Uses

The fat-soluble vitamin D’s most important role is maintaining blood levels of calcium, which it accomplishes by increasing absorption of calcium from food and reducing urinary calcium loss. Both effects keep calcium in the body and therefore spare the calcium that is stored in bones. When necessary, vitamin D transfers calcium from the bone into the bloodstream, which does not benefit bones. Although the overall effect of vitamin D on the bones is complicated, some vitamin D is necessary for healthy bones and teeth.

When "D” is used without a subscript it refers to either D2 or D3, the two primary forms used as supplements.    

What Are Star Ratings?

Our proprietary “Star-Rating” system was developed to help you easily understand the amount of scientific support behind each supplement in relation to a specific health condition. While there is no way to predict whether a vitamin, mineral, or herb will successfully treat or prevent associated health conditions, our unique ratings tell you how well these supplements are understood by the medical community, and whether studies have found them to be effective for other people.

For over a decade, our team has combed through thousands of research articles published in reputable journals. To help you make educated decisions, and to better understand controversial or confusing supplements, our medical experts have digested the science into these three easy-to-follow ratings. We hope this provides you with a helpful resource to make informed decisions towards your health and well-being.

3 Stars Reliable and relatively consistent scientific data showing a substantial health benefit.

2 Stars Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.

1 Star For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support.

This supplement has been used in connection with the following health conditions:

Used for Why
3 Stars
Crohn’s Disease
1,000 to 1,200 IU daily under medical supervision
Vitamin D malabsorption is common in Crohn’s and can lead to a deficiency of the vitamin. Supplementation can help prevent bone loss in cases of deficiency.

Vitamin D malabsorption is common in Crohn’s and can lead to a deficiency of the vitamin. Successful treatment with vitamin D for osteomalacia (bone brittleness caused by vitamin D deficiency) triggered by Crohn’s disease has been reported. Another study found 1,000 IU per day of vitamin D prevented bone loss in people with Crohn’s, while an unsupplemented group experienced significant bone loss. In addition, in a double-blind trial, vitamin D supplementation (1,200 IU per day for 12 months) prevented relapses in patients with Crohn's disease in remission. The patients in that study had normal vitamin D status prior to receiving vitamin D supplementation. In a preliminary study of patients with mild-to-moderate Crohn's disease, vitamin D supplementation for 24 weeks was associated with an improvement in disease activity. The amount used in that study was 1,000 to 5,000 IU per day, based on blood levels of the vitamin. A doctor should be consulted to determine the right level of vitamin D for supplementation.

3 Stars
Cystic Fibrosis
1,000 to 2,000 IU daily
The fat malabsorption associated with cystic fibrosis often leads to a deficiency of fat-soluble vitamins, such as vitamin D. Supplementation can help counteract the deficiency.

The fat malabsorption associated with CF often leads to a deficiency of fat-soluble vitamins. Oral supplementation of these nutrients is considered crucial to maintaining good nutritional status. Current recommendations for supplementation are as follows: vitamin A, 5,000 to 10,000 IU/day; vitamin D, 1,000 to 2,000 IU/day; vitamin E, 100 to 300 IU/day; and vitamin K, 5 mg every three days. Of the water-soluble vitamins, only vitamin B12 is poorly absorbed in cystic fibrosis, and taking pancreatic enzymes helps prevent B12 deficiencies.

3 Stars
Osteoporosis
400 to 800 IU daily depending on age, sun exposure, and dietary sources
Vitamin D increases calcium absorption and helps make bones stronger. Vitamin D supplementation has reduced bone loss in women who don’t get enough of the vitamin from food and slowed bone loss in people with osteoporosis and in postmenopausal women. It also works with calcium to prevent some musculoskeletal causes of falls and subsequent fractures.

Vitamin D increases calcium absorption, and blood levels of vitamin D are directly related to the strength of bones. Mild deficiency of vitamin D is common in the fit, active elderly population and leads to an acceleration of age-related loss of bone mass and an increased risk of fracture. In double-blind research, vitamin D supplementation has reduced bone loss in women who consume insufficient vitamin D from food and slowed bone loss in people with osteoporosis and in postmenopausal women. However, the effect of vitamin D supplementation on osteoporosis risk remains surprisingly unclear, with some trials reporting little if any benefit. Moreover, trials reporting reduced risk of fracture have usually combined vitamin D with calcium supplementation, making it difficult to assess how much benefit is caused by supplementation with vitamin D alone.

Impaired balance and increased body sway are important causes of falls in elderly people with osteoporosis. Vitamin D works with calcium to prevent some musculoskeletal causes of falls. In a double-blind trial, elderly women who were given 800 IU per day of vitamin D and 1,200 mg per day of calcium had a significantly lower rate of falls and subsequent fractures than did women given the same amount of calcium alone. Vitamin D in the amount of 800 IU per day effectively prevented falls in a double-blind study of elderly nursing home residents, but lower amounts were ineffective.

Despite inconsistency in the research, many doctors recommend 400 to 800 IU per day of supplemental vitamin D, depending upon dietary intake and exposure to sunlight.

One trial studying postmenopausal women combined hormone replacement therapy with magnesium (600 mg per day), calcium (500 mg per day), vitamin C, B vitamins, vitamin D, zinc, copper, manganese, boron, and other nutrients for an eight- to nine-month period. In addition, participants were told to avoid processed foods, limit protein intake, emphasize vegetable over animal protein, and limit consumption of salt, sugar, alcohol, coffee, tea, chocolate, and tobacco. Bone density increased a remarkable 11%, compared to only 0.7% in women receiving hormone replacement alone.

3 Stars
Rickets
Consult a qualified healthcare practitioner
Vitamin D supplements may be helpful in preventing and treating rickets.

Vitamin D and calcium supplements should be used to treat rickets only if a medical professional has diagnosed rickets and has also determined the cause is a nutritional deficiency. Amounts needed to treat rickets should be determined by a doctor and will depend on the age, weight, and condition of the child. For prevention of rickets, 400 IU of vitamin D per day is considered reasonable. Doctors often suggest 1,600 IU per day for treating rickets caused by a lack of dietary vitamin D.

3 Stars
Vitamin D Deficiency
Vitamin D deficiency should be diagnosed by a doctor
One in seven adults has been reported to be deficient in vitamin D. In adults, vitamin D deficiency may result in a softening of the bones known as osteomalacia.

In adults, vitamin D deficiency may result in a softening of the bones known as osteomalacia. This condition is treated with vitamin D, sometimes in combination with calcium supplements. Osteomalacia should be diagnosed, and its treatment monitored, by a doctor. In people of any age, vitamin D deficiency causes abnormal bone formation. It occurs more commonly following winter, owing to restricted sunlight exposure during that season. Living in an area with a lot of atmospheric pollution, which can block the sun's ultraviolet rays, also appears to increase the risk of vitamin D deficiency.[REF] [REF]

Vitamin D deficiency is more common in strict vegetarians (who avoid vitamin D-fortified dairy foods), dark-skinned people,[REF] alcoholics, and people with liver or kidney disease. People with liver and kidney disease can make vitamin D but cannot activate it.

Vitamin D deficiency is more common in people suffering from intestinal malabsorption, which may have occurred following previous intestinal surgeries, or from celiac disease.[REF] People with insufficient pancreatic function (for example, those with pancreatitis or cystic fibrosis) tend to be deficient in vitamin D. Vitamin D deficiency is also common in individuals with hyperthyroidism (Graves' disease), particularly women.[REF]

In children, vitamin D deficiency is called rickets and causes a bowing of bones not seen in adults with vitamin D deficiency. Vitamin D deficiency is common among people with hyperparathyroidism, a condition in which the parathyroid gland is overactive. In a study of 124 people with mild hyperparathyroidism, vitamin D levels were below normal in 7% of them and suboptimal in 53% of them.[REF] Vitamin D deficiency is also common in men with advanced prostate cancer. In one study, 44% of 16 men with advanced prostate cancer had decreased blood levels of vitamin D.[REF]

One in seven adults has been reported to be deficient in vitamin D.[REF] In one study, 42% of hospitalized patients under age 65 were reported to be vitamin D deficient.[REF] In this same study, 37% of the people were found to be deficient in vitamin D, despite the fact they were eating the currently recommended amount of this nutrient. Vitamin D deficiency is particularly common among the elderly. Age-related decline in vitamin D status may be due to reduced absorption, transport, or liver metabolism of vitamin D.[REF]

2 Stars
Asthma
1,200 IU per day for 15 to 17 weeks
One study found that daily supplementation with vitamin D during the winter months significantly reduced the amount of times the children experienced asthma attacks.
In a double-blind study of Japanese children (average age, ten years), supplementation with 1,200 IU per day of vitamin D for 15 to 17 weeks during the winter significantly reduced the incidence of asthma attacks compared with a placebo. In another double-blind study, however, vitamin D (2,000 IU per day for 15 weeks) did not provide any clear benefit in children with asthma. Vitamin D has not been found to be beneficial for adults with asthma.
2 Stars
Autism
Refer to label instructions
In a preliminary study and a follow-up double-blind study of autistic children, daily supplementation with vitamin D was associated with improvements in various symptoms of autism.
In a preliminary study and a follow-up double-blind study of Egyptian autistic children, daily supplementation with vitamin D for 3 to 4 months was associated with improvements in various symptoms of autism, including irritability, hyperactivity, social withdrawal, inappropriate speech, stereotypical behavior, and communication.. The amount of vitamin D given was 136 IU per pound of body weight, with a maximum of 5,000 IU per day. Since the amount of vitamin D used in the study was relatively large and could potentially cause adverse effects, this treatment should be monitored by a doctor.
2 Stars
Burns
200 to 600 IU day in cases of extensive burns
People with a history of an extensive burn might benefit from vitamin D supplementation, since the skin may not be as effective at manufacturing vitamin D from sunlight.

Burns affecting a large proportion of the body may result in vitamin D deficiency, potentially increasing the risk of osteoporosis, which is a frequent long-term consequence of severe burns. Vitamin D deficiency may result from the inability of previously burned skin to manufacture vitamin D after exposure to sunlight. People with a history of an extensive burn might benefit from vitamin D supplementation.

2 Stars
Celiac Disease
Consult a qualified healthcare practitioner
Malabsorption-induced vitamin D deficiency can lead to bone weakening in people with celiac disease. Supplementing with vitamin D may help increase bone density.

The malabsorption that occurs in celiac disease can lead to multiple nutritional deficiencies. The most common nutritional problems in people with celiac disease include deficiencies of essential fatty acids, iron, vitamin D, vitamin K, calcium, magnesium, and folic acid.Zinc malabsorption also occurs frequently in celiac disease and may result in zinc deficiency, even in people who are otherwise in remission. People with newly diagnosed celiac disease should be assessed for nutritional deficiencies by a doctor. Celiac patients who have not yet completely recovered should supplement with a high-potency multivitamin-mineral. Some patients may require even higher amounts of some of these vitamins and minerals—an issue that should be discussed with their healthcare practitioner. Evidence of a nutrient deficiency in a celiac patient is a clear indication for supplementation with that nutrient.

After commencement of a gluten-free diet, overall nutritional status gradually improves. However, deficiencies of some nutrients may persist, even in people who are strictly avoiding gluten. For example, magnesium deficiency was found in 8 of 23 adults with celiac disease who had been following a gluten-free diet and were symptom-free. When these adults were supplemented with magnesium for two years, their bone mineral density increased significantly.

Malabsorption-induced depletion of vitamin D can lead to osteomalacia (defective bone mineralization) in people with celiac disease. Although supplementation with vitamin D appears to increase bone density, the excess risk of bone fracture may not be entirely eliminated.

2 Stars
Common Cold and Sore Throat
300 IU per day for three months in winter
Research suggests that supplementing with vitamin D may prevent upper respiratory tract infections in people who are deficient in the vitamin, but not in those who have normal vitamin D status.
In a double-blind trial, supplementation with 300 IU per day of vitamin D for three months during the winter decreased the frequency of upper respiratory tract infections in Mongolian children with vitamin D deficiency. Vitamin D supplementation also decreased the incidence of colds in several other studies, but was ineffective in other research. In one of the negative studies, vitamin D supplementation significantly increased the incidence of colds among African Americans, but not in the entire study population. While it is not certain why the results differed in the different studies, vitamin D seems to be most effective in children, in adults with frequent respiratory infections, and possibly in people with low baseline vitamin D status.
2 Stars
Congestive Heart Failure
Refer to label instructions
In preliminary research, the prevalence of vitamin D deficiency was significantly higher in patients with congestive heart failure than in patients without it.
In one study, the prevalence of vitamin D deficiency was significantly higher in patients with CHF than in patients without CHF (28% vs. 22%). In that study, heart failure patients who received vitamin D supplementation (usually 800 to 1,000 IU per day) had a 32% lower death rate, compared with heart failure patients who did not receive vitamin D supplementation. In a double-blind study of elderly people who had suffered a fracture, supplementing with 800 IU per day of vitamin D for 2 to 5 years significantly decreased the incidence of CHF by 25%, compared with a placebo.
2 Stars
Depression
400 to 800 IU daily
Some studies have shown that supplementing with vitamin D leads to improved mood.

Blood levels of vitamin D (measured as 25-hydroxyvitamin D) have been found to be significantly lower in people with depression than in healthy people. Vitamin D supplementation may be associated with elevations in mood. In a double-blind trial, healthy people were given 400–800 IU per day of vitamin D3, or no vitamin D3, for five days during late winter. Results showed that vitamin D3 significantly enhanced positive mood and there was some evidence of a reduction in negative mood compared to a placebo. In another double-blind trial, people without depression took 600 IU of vitamin D along with 1,000 mg of calcium, or a placebo, twice daily for four weeks. Compared to the placebo, combined vitamin D and calcium supplementation produced significant elevations in mood that persisted at least one week after supplementation was discontinued. In still another double-blind trial, the combination of 1,500 IU per day of vitamin D and the antidepressant drug fluoxetine was more effective than fluoxetine alone in the treatment of major depression.

2 Stars
Eczema
Refer to label instructions
In one preliminary trial, eczema significantly improved in people who had very low blood levels of vitamin D after supplementing with vitamin D.
In a preliminary trial, adults with eczema who had very low blood levels of vitamin D (measured as 25-hydroxyvitamin D) had a significant improvement in their eczema after supplementing with 2,000 IU of vitamin D per day for three months. In a double-blind trial, there was a significantly greater improvement of winter-related eczema in children who received 1,000 IU per day of vitamin D for 1 month than in those who received a placebo. However, in another double-blind trial, supplementation with 4,000 IU per day of vitamin D for 3 weeks was not beneficial for adults with eczema. In that trial, blood levels of vitamin D were normal or slightly low prior to treatment.
2 Stars
Epilepsy
Refer to label instructions
In a preliminary study, correcting vitamin D deficiency resulted in a decrease in the number of seizures in patients with epilepsy who had failed to respond adequately to medications.
Vitamin D deficiency is common in people with epilepsy, partly because some anticonvulsant drugs deplete vitamin D. In a preliminary study, correcting vitamin D deficiency resulted in a decrease in the number of seizures in patients with epilepsy who had failed to respond adequately to medications.
2 Stars
Fibromyalgia
Refer to label instructions
In a double-blind study of women with fibromyalgia who had low or moderately low blood levels of vitamin D, supplementing with vitamin D improved pain, compared with a placebo.
In a double-blind study of women with fibromyalgia who had low or moderately low blood levels of vitamin D (25-hydroxyvitamin D), supplementing with vitamin D for 24 weeks improved pain, compared with a placebo. The amount of vitamin D used was 1,200 to 2,400 IU per day, depending on the blood level of vitamin D. The amount given was adjusted during the study, to maintain blood levels of vitamin D between 32 ng/ml and 48 ng/ml.
2 Stars
Hypertension
800 to 2,000 IU daily
In one trial, women with low blood levels of vitamin D who were given calcium supplement plus vitamin D experienced significantly reduced systolic blood pressure.
In a double-blind trial, women with low blood levels of vitamin D (measured as 25-hydroxyvitamin D3) were given a calcium supplement, plus either 800 IU of vitamin D per day or a placebo for eight weeks. Compared with the placebo, vitamin D significantly reduced systolic blood pressure by an average of 9.3%, but did not affect diastolic blood pressure.In another double-blind trial, vitamin D supplementation (1,000, 2,000, or 4,000 IU per day) for 3 months produced a modest but statistically significant decrease in systolic but not diastolic blood pressure in African Americans who had low blood levels of vitamin D. The reduction in blood pressure was greater with higher amounts of vitamin D intake.
2 Stars
Influenza
800 IU per day for two years; then 2,000 IU per day after that
In one study, long-term vitamin D supplementation for three years significantly reduced flu and cold symptoms.

In a double-blind study, African Americans who received vitamin D supplements for three years had significantly fewer symptoms of influenza or colds, when compared with women who received a placebo. The amount of vitamin D was 800 IU per day for the first two years, followed by 2,000 IU per day for one year.

2 Stars
Influenza and Children
1,200 IU per day for 15 to 17 weeks
A study of Japanese children found that daily supplementation with vitamin D during the winter months significantly reduced the amount of times the children developed the flu.
In a double-blind study of Japanese children (average age, ten years), supplementation with 1,200 IU per day of vitamin D for 15 to 17 weeks during the winter significantly reduced the incidence of influenza infections by 42%, compared with a placebo.
2 Stars
Low Back Pain
Refer to label instructions
In people with muscle pain associated with vitamin D deficiency, supplementing with the vitamin may improve pain.
Some studies have found that vitamin D levels are lower in people with back pain than in healthy people. In patients with muscle pain associated with vitamin D deficiency, vitamin D supplementation has resulted in improvement in the pain.
2 Stars
Lupus
Refer to label instructions
In a double-blind trial, people who took vitamin D daily experienced a decrease in disease activity and flare-ups.
People with SLE frequently have low blood levels of vitamin D (measured as 25-hydroxyvitamin D). In a double-blind trial, supplementing with 2,000 IU per day of vitamin D for 12 months significantly decreased disease activity by an average of 37%, compared with a placebo. In addition, the proportion of patients who experienced a disease flare during the study was significantly lower in the vitamin D group than in the placebo group (10% vs. 24%). Vitamin D in the amount of 50,000 IU once a week for 24 weeks also decreased disease activity in another study. A few patients taking vitamin D in the first study developed elevated levels of calcium in the blood or urine. Therefore, SLE patients interested in taking vitamin D supplements should be monitored by a doctor.
2 Stars
Neuropathy
2,000 IU of vitamin D per day for three months
In a preliminary trial, supplementing with vitamin D per day significantly improved pain by almost 50% in patients with diabetic neuropathy.
A preliminary trial supplementation with about 2,000 IU of vitamin D per day for 3 months significantly improved pain by almost 50% in patients with diabetic neuropathy.
2 Stars
Seasonal Affective Disorder
Refer to label instructions
Supplementing with vitamin D may improve SAD in people with low levels of the vitamin.

Vitamin D is well known for its effects on helping to maintain normal calcium levels, but it also exerts influence on the brain, spinal cord, and hormone-producing tissues of the body that may be important in the regulation of mood.

In one study, people with SAD were randomly assigned to receive either 100,000 IU of vitamin D one time only or two hours of bright-light therapy every day for one month. After one month, researchers observed a significant improvement in depression in the group that received vitamin D, but not in the group given light therapy. However, another double-blind study found that supplementation with 2,800 IU per day of vitamin D during the winter was not beneficial for people with SAD. Most of the participants in the study in which vitamin D was beneficial were deficient in vitamin D, whereas most of the participants in the negative study were not deficient. While additional research needs to be done, current evidence suggests that vitamin D supplementation may improve SAD in people with vitamin D deficiency but not in people without vitamin D deficiency.

2 Stars
Tension Headache (Calcium)
1,000 to 1,500 mg per day (plus the same amount of calcium)
In preliminary research, people with chronic tension-type headaches who were also suffering from severe vitamin D deficiency experienced an improvement in their symptoms after supplementing with vitamin D and calcium.
In a preliminary trial, eight patients had chronic tension-type headache in association with severe vitamin D deficiency. In each case, the headaches resolved after treatment with vitamin D3 (1,000 to 1,500 IU per day) and calcium (1,000 to 1,500 mg per day).
2 Stars
Type 1 Diabetes
Consult a qualified healthcare practitioner
Vitamin D is needed to maintain adequate insulin levels, and supplementing with it may reduce the risk of developing type 1 diabetes.
Vitamin D is needed to maintain adequate blood levels of insulin. Vitamin D receptors have been found in the pancreas where insulin is made and some, but not all preliminary evidence suggests that supplementation might reduce the risk of developing type 1 diabetes. Vitamin D supplementation may also slow the decline of pancreatic function in people with newly diagnosed type 1 diabetes who have not yet suffered an extensive loss of pancreatic function. Not enough is known about optimal amounts of vitamin D for people with diabetes, and high amounts of vitamin D can be toxic. Therefore, people with diabetes considering vitamin D supplementation should talk with a doctor and have their vitamin D status assessed.
2 Stars
Type 2 Diabetes
1,332 IU daily
Vitamin D is needed to maintain adequate insulin levels, and supplementing with it may improve blood sugar control in people with type 2 diabetes.
Vitamin D is needed to maintain adequate blood levels of insulin. Vitamin D receptors have been found in the pancreas where insulin is made. Some, but not all, preliminary trials have found that supplementation can improve some measures of blood sugar control in people with type 2 diabetes. In addition, in a preliminary trial supplementation with about 2,000 IU of vitamin D per day for three months significantly improved pain by almost 50% in patients with diabetic neuropathy. Not enough is known about optimal amounts of vitamin D for people with diabetes, and high amounts of vitamin D can be toxic; therefore, people with diabetes considering vitamin D supplementation should talk with a doctor and have their vitamin D status assessed.
2 Stars
Type 2 Diabetes and Diabetic Neuropathy
2,000 IU of vitamin D per day for three months
In a preliminary trial, supplementing with vitamin D per day significantly improved pain by almost 50% in patients with diabetic neuropathy.
A preliminary trial supplementation with about 2,000 IU of vitamin D per day for 3 months significantly improved pain by almost 50% in patients with diabetic neuropathy.
2 Stars
Vaginitis
Refer to label instructions
In one double-blind trial, women with vaginitis who were not experiencing any symptoms were given vitamin D daily and had a higher cure rate than the control group.
In a double-blind trial, women with bacterial vaginosis who were not experiencing any symptoms were given 2,000 IU of vitamin D per day or no vitamin D (control group) for 15 weeks. The cure rate was significantly higher in the vitamin D group than in the control group (63.5% vs. 19.2%). Vitamin D is thought to work by improving the functioning of the immune system.
1 Star
Alcohol Withdrawal
Refer to label instructions
If deficient, supplementing with this vitamin may help prevent bone loss and muscle weakness.

Although the incidence of B-complex deficiencies is known to be high in alcoholics, the incidence of other vitamin deficiencies remains less clear. Nonetheless, deficiencies of vitamin A, vitamin D, vitamin E, and vitamin C are seen in many alcoholics. While some reports have suggested it may be safer for alcoholics to supplement with beta-carotene instead of vitamin A, potential problems accompany the use of either vitamin A or beta-carotene in correcting the deficiency induced by alcoholism. These problems result in part because the combinations of alcohol and vitamin A or alcohol and beta-carotene appear to increase potential damage to the liver. Thus, vitamin A-depleted alcoholics require a doctor’s intervention, including supplementation with vitamin A and beta-carotene accompanied by assessment of liver function. Supplementing with vitamin C, on the other hand, appears to help the body rid itself of alcohol. Some doctors recommend 1 to 3 grams per day of vitamin C.

1 Star
Amenorrhea and Osteoporosis (Calcium)
Refer to label instructions
Despite the lack of evidence that calcium and vitamin D supplements alone are helpful to amenorrheic women, they are still generally recommended to prevent the added burden of calcium and vitamin D deficiency from further contributing to bone loss.

A preliminary trial showed that bone loss occurred over a one-year period in amenorrheic exercising women despite daily supplementation with 1,200 mg of calcium and 400 IU of vitamin D. In a controlled study of amenorrheic nursing women, who ordinarily experience brief bone loss that reverses when menstruation returns, bone loss was not prevented by a multivitamin supplement providing 400 IU of vitamin D along with 500 mg twice daily of calcium or placebo. Despite the lack of evidence that calcium and vitamin D supplements alone are helpful to amenorrheic women, they are still generally recommended to prevent the added burden of calcium and vitamin D deficiency from further contributing to bone loss. Amounts typically recommended are 1,200 to 1,500 mg calcium and 400 to 800 IU vitamin D daily.

1 Star
Breast Cancer
Refer to label instructions
Vitamin D from supplements and from exposure to the sun both appear to protect against breast cancer.

Breast cancer rates have been reported to be relatively high in areas of low exposure to sunlight. Sunlight triggers the formation of vitamin D in the skin, which can be activated in the liver and kidneys into a hormone with great activity. This activated form of vitamin D causes “cellular differentiation”—essentially the opposite of cancer.

The following evidence indicates that vitamin D might have a protective role against breast cancer:

  • Synthetic vitamin D-like molecules have prevented the equivalent of breast cancer in animals.
  • Activated vitamin D appears to have antiestrogenic activity.
  • Both sunlight and dietary exposure to vitamin D have correlated with a reduced risk of breast cancer.

Activated vitamin D comes in several forms. One of them—1,25 dihydroxycholecalciferol—is an exact duplicate of the hormone made in the human body.

The following preliminary, non-clinical evidence supports the idea that activated vitamin D may be of help to some breast cancer patients:

  • In combination with tamoxifen, a synthetic, activated-vitamin D-like molecule has inhibited the growth of breast cancer cells in test tube research.
  • Synthetic vitamin D-like molecules induce tumor cell death in breast cancer cells.
  • Activated vitamin D suppresses the growth of human cancer cells transplanted into animals.
  • In test tube research, activated vitamin D has increased the anticancer action of chemotherapy.

In a preliminary trial, activated vitamin D was applied topically to the breast, once per day for six weeks, in 19 patients with breast cancer. Of the 14 patients who completed the trial, three showed a large reduction in tumor size, and one showed a minor improvement. Those who responded had tumors that contained receptors for activated vitamin D. However, other preliminary reports have not found that high levels of these receptors consistently correlate with a better outcome.

With a doctor’s prescription, compounding pharmacists can put activated vitamin D, a hormone, into a topical ointment. Due to potential toxicity, use of this hormone, even topically, requires careful monitoring by a physician. Standard vitamin D supplements are unlikely to duplicate the effects of activated vitamin D in women with breast cancer. The patients in the breast cancer trial all had locally advanced disease.

1 Star
Cardiac Arrhythmia
Refer to label instructions
One case report described relief from a type of arrhythmia after supplementing with vitamin D.

One case of long-standing sick-sinus syndrome (another type of arrhythmia) was reported to resolve upon supplementation with 800 IU per day of vitamin D prescribed for an unrelated condition. However, it was not clear from that report whether the improvement was due to the vitamin D. More research is needed.

1 Star
Colon Cancer
Refer to label instructions
People who take vitamin D supplements have been shown to be at low risk for colon cancer.

Ultraviolet light from sun exposure increases the risk of skin cancers and melanoma. Nonetheless, where sun exposure is low, rates of several cancers have been reported to be high. An association between greater sun exposure and a reduced risk of colon cancer has appeared in some, but not all, studies.

In preliminary reports, people who take vitamin D supplements have been reported to be at low risk for colon cancer, though the differences between supplement takers and others might have been due to chance. More research is needed to determine whether vitamin D supplements may be useful in connection with the prevention of colon cancer.

1 Star
Dysmenorrhea
Refer to label instructions
In a double-blind trial, women with dysmenorrhea received a placebo or a single administration of a large amount of vitamin D, which appeared to significantly diminish menstrual pain. This should only be done under doctor supervision.
In a double-blind trial, women with dysmenorrhea received a placebo or a single administration of a large amount of vitamin D (300,000), five days before the expected onset of the next menstrual period. During the next two menstrual periods, menstrual pain was significantly lower in the vitamin D group than in the placebo group. Such a large amount of vitamin D should be given only under the supervision of a doctor. Further research is needed to determine whether daily supplementation of a smaller amount (such as 800 to 2,000 IU per day) would have a similar beneficial effect.
1 Star
Hepatitis and Hepatitis C
Refer to label instructions
In a study of people with hepatitis C who were being treated with standard medication, vitamin D supplementation increased the proportion of patients who had undetectable levels of the virus after 24 weeks of treatment.
In a study of people with hepatitis C (genotype 1b) who were being treated with standard medication (pegylated interferon and ribavirin), vitamin D supplementation (1,000 IU per day) increased the proportion of patients who had undetectable levels of the virus after 24 weeks of treatment (79% vs. 55%).
1 Star
Migraine Headache
Refer to label instructions
Taking large amounts of the combination of calcium and vitamin D has been reported to produce a marked reduction in the incidence of migraines in several women.

Taking large amounts of the combination of calcium (1,000 to 2,000 mg per day) and vitamin D has been reported to produce a marked reduction in the incidence of migraines in several women. However, the amount of vitamin D given to these women (usually 50,000 IU once a week), can cause adverse reactions, particularly when used in combination with calcium. This amount of vitamin D should be used only under medical supervision. Doctors often recommend that people take 800 to 1,200 mg of calcium and 400 IU of vitamin D per day. However, it is not known whether theses amounts would have an effect on migraines.

1 Star
Multiple Sclerosis
Refer to label instructions
Studies suggest that vitamin D may help reduce the number of MS attacks and may protect against the development of the disease.
Animal studies have demonstrated that vitamin D can prevent an experimental form of multiple sclerosis. In humans, striking geographical differences in the prevalence of multiple sclerosis suggest that sun exposure (which promotes the synthesis of vitamin D) may protect against the development of the disease. In addition, higher blood levels of vitamin D are associated with a lower risk of developing MS. However, no clinical trials have been done to determine whether increasing vitamin D intake or sunlight exposure would prevent MS.

In a preliminary trial, treatment with very large amounts of vitamin D (more than 10,000 IU per day) was associated with a decrease in the number of relapses in patients with MS; however, the decrease was not statistically significant. In a double-blind study of patients with MS, a large amount of vitamin D (approximately 10,000 IU per day), when compared with a moderate amount (1,000 IU per day), resulted in a significant increase in the relapse rate and in the degree of disability. Based on the available evidence, large amounts of vitamin D cannot be recommended as a treatment for MS. Additional research is needed to determine whether moderate amounts of vitamin D would be beneficial.

1 Star
Parkinson’s Disease
Refer to label instructions
Vitamin D deficiency is common in Parkinson’s disease and may increase the risk of hip fracture due to osteoporosis. This risk may be reduced by taking vitamin D.

Vitamin D deficiency is common in Parkinson’s disease. In a double-blind trial, supplementation with 1,200 IU per day of vitamin D for 1 year slowed the progression of Parkinson's disease, compared with a placebo.

In people with Parkinson's disease, vitamin D deficiency combined with reduced levels of activity may increase the risk of developing osteoporosis. Low vitamin D levels in Parkinson’s disease have been reported to increase the risk of hip fracture due to osteoporosis. This risk has been significantly reduced with the use of synthetic, activated vitamin D—a prescription drug. Whether the same effect could be achieved with supplemental vitamin D remains unknown, though some doctors recommend 400–1,000 IU vitamin D per day. People with Parkinson’s disease may wish to discuss the use of synthetic activated vitamin D with a healthcare professional.

1 Star
Prostate Cancer
2,000 IU daily
Where sun exposure is low, the rate of prostate cancer has been reported to be high.
Where sun exposure is low, the rate of prostate cancer has been reported to be high. In the body, vitamin D is changed into a hormone with great activity. This activated vitamin D causes “cellular differentiation”—essentially the opposite of cancer.
1 Star
Restless Legs Syndrome
Refer to label instructions
In one small study, in people with a vitamin D blood level below 20 ng/ml, vitamin D supplementation decreased the severity of restless legs syndrome.
In a study of 12 Saudi Arabian adults, the average blood level of vitamin D (measured as 25-hydroxyvitamin D) was very low (8.7 ng/ml). In people with a level below 20 ng/ml, vitamin D supplementation decreased the severity of restless legs syndrome by 62%. Double-blind trials are needed to confirm this study
1 Star
Urinary Incontinence
Refer to label instructions
Higher blood levels of vitamin D are associated with lower risk of urinary incontinence in women.
Vitamin D may be important for normal muscle function, including muscles that help control urinary continence. Higher blood levels of vitamin D are associated with lower risk of urinary incontinence in women, according to one preliminary study. Controlled trials are needed to determine whether vitamin D supplements can help prevent or treat urinary incontinence.
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Vitiligo
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When used in combination with sun exposure, a form of vitamin D called calcipotriol may be effective in stimulating repigmentation in children with vitiligo.

When used topically in combination with sun exposure, a pharmaceutical form of vitamin D, called calcipotriol, may be effective in stimulating repigmentation in children with vitiligo. In a preliminary study, children applied a cream containing calcipotriol daily and exposed themselves to sunlight for 10–15 minutes the following morning. After 11 months, marked to complete repigmentation occurred in 55% of the children, moderate repigmentation occurred in 22%, and little or no improvement was seen in 22%. None of the children developed new areas of vitiligo. The first evidence of repigmentation occurred within 6 to 12 weeks in the majority of the children. All participants tolerated the cream well, with approximately 17% complaining of mild, transient skin irritation. Calcipotriol is a prescription medication to be used only under the supervision of a doctor. It is not known whether vitamin D as a dietary supplement has any effect on vitiligo.

How It Works

How to Use It

People who get plenty of sun exposure do not require supplemental vitamin D, since sunlight increases vitamin D synthesis when it strikes bare skin. Although the recommended dietary allowance for vitamin D is 200 IU per day for adults, there is some evidence that elderly people need 800 to 1,000 IU per day for maximum effects on preserving bone density and preventing fractures.1 , 2 , 3 , 4 Sun-deprived people should take no less than 600 IU per day and ideally around 1,000 IU per day.5 , 6

Where to Find It

Cod liver oil is an excellent dietary source of vitamin D, as are vitamin D-fortified foods. Traces of vitamin D are found in egg yolks and butter. However, the majority of vitamin D in the body is created during a chemical reaction that starts with sunlight exposure to the skin. Cholecalciferol (vitamin D3) is the animal form of this vitamin.

Possible Deficiencies

In adults, vitamin D deficiency may result in a softening of the bones known as osteomalacia. This condition is treated with vitamin D, sometimes in combination with calcium supplements. Osteomalacia should be diagnosed, and its treatment monitored, by a doctor. In people of any age, vitamin D deficiency causes abnormal bone formation. In addition, vitamin D deficiency can cause muscle weakness, which improves with vitamin D supplementation.7 Vitamin D deficiency occurs more commonly following winter, owing to restricted sunlight exposure during that season. Living in an area with a lot of atmospheric pollution, which can block the sun's ultraviolet rays, also appears to increase the risk of vitamin D deficiency.8 9

Vitamin D deficiency is more common in strict vegetarians (who avoid vitamin D-fortified dairy foods), dark-skinned people,10 alcoholics, and people with liver or kidney disease. People with liver and kidney disease can make vitamin D but cannot activate it.

Vitamin D deficiency is more common in people suffering from intestinal malabsorption, which may have occurred following previous intestinal surgeries, or from celiac disease.11 People with insufficient pancreatic function (e.g., those with pancreatitis or cystic fibrosis) tend to be deficient in vitamin D. Vitamin D deficiency is also common in individuals with hyperthyroidism (Graves' disease), particularly women.12

In children, vitamin D deficiency is called rickets and causes a bowing of bones not seen in adults with vitamin D deficiency. Vitamin D deficiency is common among people with hyperparathyroidism, a condition in which the parathyroid gland is overactive. In a study of 124 people with mild hyperparathyroidism, vitamin D levels were below normal in 7% of them and suboptimal in 53% of them.13 Vitamin D deficiency is also common in men with advanced prostate cancer. In one study, 44% of 16 men with advanced prostate cancer had decreased blood levels of vitamin D.14

One in seven adults has been reported to be deficient in vitamin D.15 In one study, 42% of hospitalized patients under age 65 were reported to be vitamin D deficient.16 In this same study, 37% of the people were found to be deficient in vitamin D, despite the fact they were eating the currently recommended amount of this nutrient. Vitamin D deficiency is particularly common among the elderly. Age-related decline in vitamin D status may be due to reduced absorption, transport, or liver metabolism of vitamin D.17

Best Form to Take

Vitamin D3 (cholecalciferol) is the form of vitamin D produced in the skin from sunlight exposure, and is also the form of vitamin D present in food. As a supplement, therefore, it is to be preferred over vitamin D2 (ergocalciferol).18

Interactions

Interactions with Supplements, Foods, & Other Compounds

Vitamin D increases both calcium and phosphorus absorption and has also been reported to increase aluminum absorption.19

Interactions with Medicines

Certain medicines interact with this supplement.

Types of interactions: Beneficial Adverse Check

Replenish Depleted Nutrients

  • Amphotericin B

    Oral corticosteroids have been found to increase urinary loss of vitamin K, vitamin C, selenium, and zinc. The importance of these losses is unknown.

  • Amphotericin B Chol Sulf Cmplx

    Oral corticosteroids have been found to increase urinary loss of vitamin K, vitamin C, selenium, and zinc. The importance of these losses is unknown.

  • Amphotericin B Lipid Complex

    Oral corticosteroids have been found to increase urinary loss of vitamin K, vitamin C, selenium, and zinc. The importance of these losses is unknown.

  • Amphotericin B Liposome

    Oral corticosteroids have been found to increase urinary loss of vitamin K, vitamin C, selenium, and zinc. The importance of these losses is unknown.

  • Carbamazepine

    Though research results vary, long-term use of anticonvulsant drugs appears to interfere with vitamin D activity, which might lead to softening of bones (osteomalacia). One study showed that blood levels of vitamin D in males taking anticonvulsants were lower than those found in men who were not taking seizure medication. In a controlled study, bone strength improved in children taking anticonvulsant drugs who were supplemented with the activated form of vitamin D and 500 mg per day of calcium for nine months. Some research suggests that differences in exposure to sunlight—which normally increases blood levels of vitamin D—might explain why some studies have failed to find a beneficial effect of vitamin D supplementation. In one controlled study, blood vitamin D levels in children taking anticonvulsants were dramatically lower in winter months than in summer months. Another study of 450 people in Florida taking anticonvulsants found that few had drug-induced bone disease. Consequently, people taking anticonvulsant drugs who do not receive adequate sunlight should supplement with 400 IU of vitamin D each day to help prevent osteomalacia.

  • Cholestyramine

    Bile acid sequestrants may prevent absorption of folic acid and the fat-soluble vitamins A, D, E, and K. Other medications and vitamin supplements should be taken one hour before or four to six hours after bile acid sequestrants for optimal absorption. Animal studies suggest calcium and zinc may also be depleted by taking cholestyramine.

  • Cimetidine

    Cimetidine may reduce vitamin D activation by the liver. Lab tests can measure activated vitamin D levels in the blood. Forms of vitamin D that do not require liver activation are available, but only by prescription.

  • Colesevelam

    Bile acid sequestrants may prevent absorption of folic acid and the fat-soluble vitamins A, D, E, and K. Other medications and vitamin supplements should be taken one hour before or four to six hours after bile acid sequestrants for optimal absorption. Animal studies suggest calcium and zinc may also be depleted by taking cholestyramine.

  • Colestipol

    Bile acid sequestrants, including colestipol, may prevent absorption of folic acid and the fat-soluble vitamins A, D, E, K. People taking colestipol should consult with their doctor about vitamin malabsorption and supplementation. People should take other drugs and vitamin supplements one hour before or four to six hours after colestipol to improve absorption.

    Animal studies suggest calcium and zinc may be depleted by taking cholestyramine, another bile acid sequestrant. Whether these same interactions would occur with colestipol is not known.

  • Cortisone

    Oral corticosteroids have been found to increase urinary loss of vitamin K, vitamin C, selenium, and zinc. The importance of these losses is unknown.

  • Dexamethasone

    Oral corticosteroids reduce absorption of calcium and interfere with the activation and metabolism of the vitamin, increasing the risk of bone loss. Doctors can measure levels of activated vitamin D (called 1,25 dihydroxycholecalciferol) to determine whether a deficiency exists; if so, activated vitamin D is only available by prescription. A study of rheumatoid arthritis patients treated with low amounts of prednisone found that those who received 1,000 mg of calcium per day plus 500 IU of vitamin D per day for two years experienced no bone loss during that time period. An analysis of properly conducted trials concluded that supplementation with vitamin D and calcium was more effective than placebo or calcium alone in protecting against corticosteroid-induced osteoporosis. Most doctors recommend 1,000 mg of calcium and 400–800 IU vitamin D per day for the prevention of osteoporosis.

  • Diclofenac-Misoprostol

    Elevated calcium and vitamin D blood levels are commonly found in people with sarcoidosis. In one individual with sarcoidosis, taking flubiprofen lowered elevated blood calcium levels, but did not alter the concentration of vitamin D. One controlled study showed that flurbiprofen reduced blood levels of vitamin D in people with frequent calcium kidney stones. Further research is needed to determine whether flurbiprofen reduces blood calcium and vitamin D levels in healthy people.

  • Felbamate

    Though research results vary, long-term use of anticonvulsant drugs appears to interfere with vitamin D activity, which might lead to softening of bones (osteomalacia). One study showed that blood levels of vitamin D in males taking anticonvulsants were lower than those found in men who were not taking seizure medication. In a controlled study, bone strength improved in children taking anticonvulsant drugs who were supplemented with the activated form of vitamin D and 500 mg per day of calcium for nine months. Some research suggests that differences in exposure to sunlight—which normally increases blood levels of vitamin D—might explain why some studies have failed to find a beneficial effect of vitamin D supplementation. In one controlled study, blood vitamin D levels in children taking anticonvulsants were dramatically lower in winter months than in summer months. Another study of 450 people in Florida taking anticonvulsants found that few had drug-induced bone disease. Consequently, people taking anticonvulsant drugs who do not receive adequate sunlight should supplement with 400 IU of vitamin D each day to help prevent osteomalacia.

  • Heparin

    Heparin may interfere with activation of vitamin D in the body.Osteoporosis (thinning of the bone) has been reported in patients who received high amounts of heparin for several months. Osteopenia (decreased bone density) has been reported in women who received heparin therapy during pregnancy.

  • Hydroxychloroquine

    Normally, the active form of vitamin D increases the absorption of calcium into the body. In a 45-year-old woman with sarcoidosis, taking hydroxychloroquine blocked the formation of active vitamin D, which helped normalize elevated blood levels of calcium in this case. Whether hydroxychloroquine has this effect in people who don’t have sarcoidosis or elevated calcium is unknown. Until controlled research explores this interaction more thoroughly, people taking hydroxychloroquine might consider having their vitamin D and/or calcium status monitored by a health practitioner.

  • Isoniazid

    Isoniazid may interfere with the activity of other nutrients, including vitamin B3 (niacin), vitamin B12, vitamin D, and vitamin E, folic acid, calcium, and magnesium. People should consider using a daily multivitamin-mineral supplement during isoniazid therapy.

  • Levetiracetam

    Though research results vary, long-term use of anticonvulsant drugs appears to interfere with vitamin D activity, which might lead to softening of bones (osteomalacia). One study showed that blood levels of vitamin D in males taking anticonvulsants were lower than those found in men who were not taking seizure medication. In a controlled study, bone strength improved in children taking anticonvulsant drugs who were supplemented with the activated form of vitamin D and 500 mg per day of calcium for nine months. Some research suggests that differences in exposure to sunlight—which normally increases blood levels of vitamin D—might explain why some studies have failed to find a beneficial effect of vitamin D supplementation. In one controlled study, blood vitamin D levels in children taking anticonvulsants were dramatically lower in winter months than in summer months. Another study of 450 people in Florida taking anticonvulsants found that few had drug-induced bone disease. Consequently, people taking anticonvulsant drugs who do not receive adequate sunlight should supplement with 400 IU of vitamin D each day to help prevent osteomalacia.

  • Mineral Oil

    Mineral oil has interfered with the absorption of many nutrients, including beta-carotenephosphorus, potassium, and vitamins A, D, K, and E in some, but not all, research. Taking mineral oil on an empty stomach may reduce this interference. It makes sense to take a daily multivitamin-mineral supplement two hours before or after mineral oil. It is important to read labels, because many multivitamins do not contain vitamin K or contain inadequate (less than 100 mcg per day) amounts.

  • Naproxen-Esomeprazole Mag

    Elevated calcium and vitamin D blood levels are commonly found in people with sarcoidosis. In one individual with sarcoidosis, taking flubiprofen lowered elevated blood calcium levels, but did not alter the concentration of vitamin D. One controlled study showed that flurbiprofen reduced blood levels of vitamin D in people with frequent calcium kidney stones. Further research is needed to determine whether flurbiprofen reduces blood calcium and vitamin D levels in healthy people.

  • Neomycin

    Neomycin can decrease absorption or increase elimination of many nutrients, including calcium, carbohydrates, beta-carotene, fats, folic acid, iron, magnesium, potassium, sodium, and vitamin A, vitamin B12, vitamin D, and vitamin K. Surgery preparation with oral neomycin is unlikely to lead to deficiencies. It makes sense for people taking neomycin for more than a few days to also take a multivitamin-mineral supplement.

  • Nystatin

    Oral corticosteroids have been found to increase urinary loss of vitamin K, vitamin C, selenium, and zinc. The importance of these losses is unknown.

  • Orlistat

    In one well-controlled study, taking orlistat for six months resulted in reduced blood levels of vitamins A and D, though levels for most individuals remained within the normal range. However, a few people developed levels low enough to require supplementation. Other studies have shown that taking orlistat had no affect on blood vitamin A levels. Although additional research is needed, the current evidence suggests that individuals taking orlistat for more than six months should supplement with vitamins A and D.

  • Oxcarbazepine

    Though research results vary, long-term use of anticonvulsant drugs appears to interfere with vitamin D activity, which might lead to softening of bones (osteomalacia). One study showed that blood levels of vitamin D in males taking anticonvulsants were lower than those found in men who were not taking seizure medication. In a controlled study, bone strength improved in children taking anticonvulsant drugs who were supplemented with the activated form of vitamin D and 500 mg per day of calcium for nine months. Some research suggests that differences in exposure to sunlight—which normally increases blood levels of vitamin D—might explain why some studies have failed to find a beneficial effect of vitamin D supplementation. In one controlled study, blood vitamin D levels in children taking anticonvulsants were dramatically lower in winter months than in summer months. Another study of 450 people in Florida taking anticonvulsants found that few had drug-induced bone disease. Consequently, people taking anticonvulsant drugs who do not receive adequate sunlight should supplement with 400 IU of vitamin D each day to help prevent osteomalacia.

  • Phenobarbital

    Though research results vary, long-term use of anticonvulsant drugs appears to interfere with vitamin D activity, which might lead to softening of bones (osteomalacia). One study showed that blood levels of vitamin D in males taking anticonvulsants were lower than those found in men who were not taking seizure medication. In a controlled study, bone strength improved in children taking anticonvulsant drugs who were supplemented with the activated form of vitamin D and 500 mg per day of calcium for nine months. Some research suggests that differences in exposure to sunlight—which normally increases blood levels of vitamin D—might explain why some studies have failed to find a beneficial effect of vitamin D supplementation. In one controlled study, blood vitamin D levels in children taking anticonvulsants were dramatically lower in winter months than in summer months. Another study of 450 people in Florida taking anticonvulsants found that few had drug-induced bone disease. Consequently, people taking anticonvulsant drugs who do not receive adequate sunlight should supplement with 400 IU of vitamin D each day to help prevent osteomalacia.

  • Phenytoin

    Though research results vary, long-term use of anticonvulsant drugs appears to interfere with vitamin D activity, which might lead to softening of bones (osteomalacia). One study showed that blood levels of vitamin D in males taking anticonvulsants were lower than those found in men who were not taking seizure medication. In a controlled study, bone strength improved in children taking anticonvulsant drugs who were supplemented with the activated form of vitamin D and 500 mg per day of calcium for nine months. Some research suggests that differences in exposure to sunlight—which normally increases blood levels of vitamin D—might explain why some studies have failed to find a beneficial effect of vitamin D supplementation. In one controlled study, blood vitamin D levels in children taking anticonvulsants were dramatically lower in winter months than in summer months. Another study of 450 people in Florida taking anticonvulsants found that few had drug-induced bone disease. Consequently, people taking anticonvulsant drugs who do not receive adequate sunlight should supplement with 400 IU of vitamin D each day to help prevent osteomalacia.

  • Prednisolone

    Oral corticosteroids reduce absorption of calcium and interfere with the activation and metabolism of the vitamin, increasing the risk of bone loss. Doctors can measure levels of activated vitamin D (called 1,25 dihydroxycholecalciferol) to determine whether a deficiency exists; if so, activated vitamin D is only available by prescription. A study of rheumatoid arthritis patients treated with low amounts of prednisone found that those who received 1,000 mg of calcium per day plus 500 IU of vitamin D per day for two years experienced no bone loss during that time period. An analysis of properly conducted trials concluded that supplementation with vitamin D and calcium was more effective than placebo or calcium alone in protecting against corticosteroid-induced osteoporosis. Most doctors recommend 1,000 mg of calcium and 400–800 IU vitamin D per day for the prevention of osteoporosis.

  • Primidone

    Though research results vary, long-term use of anticonvulsant drugs appears to interfere with vitamin D activity, which might lead to softening of bones (osteomalacia). One study showed that blood levels of vitamin D in males taking anticonvulsants were lower than those found in men who were not taking seizure medication. In a controlled study, bone strength improved in children taking anticonvulsant drugs who were supplemented with the activated form of vitamin D and 500 mg per day of calcium for nine months. Some research suggests that differences in exposure to sunlight—which normally increases blood levels of vitamin D—might explain why some studies have failed to find a beneficial effect of vitamin D supplementation. In one controlled study, blood vitamin D levels in children taking anticonvulsants were dramatically lower in winter months than in summer months. Another study of 450 people in Florida taking anticonvulsants found that few had drug-induced bone disease. Consequently, people taking anticonvulsant drugs who do not receive adequate sunlight should supplement with 400 IU of vitamin D each day to help prevent osteomalacia.

  • Topiramate

    Though research results vary, long-term use of anticonvulsant drugs appears to interfere with vitamin D activity, which might lead to softening of bones (osteomalacia). One study showed that blood levels of vitamin D in males taking anticonvulsants were lower than those found in men who were not taking seizure medication. In a controlled study, bone strength improved in children taking anticonvulsant drugs who were supplemented with the activated form of vitamin D and 500 mg per day of calcium for nine months. Some research suggests that differences in exposure to sunlight—which normally increases blood levels of vitamin D—might explain why some studies have failed to find a beneficial effect of vitamin D supplementation. In one controlled study, blood vitamin D levels in children taking anticonvulsants were dramatically lower in winter months than in summer months. Another study of 450 people in Florida taking anticonvulsants found that few had drug-induced bone disease. Consequently, people taking anticonvulsant drugs who do not receive adequate sunlight should supplement with 400 IU of vitamin D each day to help prevent osteomalacia.

  • Zonisamide

    Though research results vary, long-term use of anticonvulsant drugs appears to interfere with vitamin D activity, which might lead to softening of bones (osteomalacia). One study showed that blood levels of vitamin D in males taking anticonvulsants were lower than those found in men who were not taking seizure medication. In a controlled study, bone strength improved in children taking anticonvulsant drugs who were supplemented with the activated form of vitamin D and 500 mg per day of calcium for nine months. Some research suggests that differences in exposure to sunlight—which normally increases blood levels of vitamin D—might explain why some studies have failed to find a beneficial effect of vitamin D supplementation. In one controlled study, blood vitamin D levels in children taking anticonvulsants were dramatically lower in winter months than in summer months. Another study of 450 people in Florida taking anticonvulsants found that few had drug-induced bone disease. Consequently, people taking anticonvulsant drugs who do not receive adequate sunlight should supplement with 400 IU of vitamin D each day to help prevent osteomalacia.

Reduce Side Effects

  • Anastrozole
    In a double-blind study, vitamin D supplementation relieved drug-induced musculoskeletal symptoms in women with breast cancer who were taking anastrozole. The amount of vitamin D used was relatively large (up to 50,000 IU of vitamin D2 once a week) and is potentially toxic. Vitamin D therapy in people taking anastrozole should therefore be prescribed and monitored by a doctor.
  • Atorvastatin
    In a preliminary trial, supplementation with vitamin D appeared to prevent muscle-related side effects in patients taking statin drugs. The amount of vitamin D used in this study was very large (up to 50,000 IU twice a week) and potentially toxic. People taking statin drugs should consult with their doctor regarding how much vitamin D can be taken.
  • Betamethasone

    Oral corticosteroids reduce absorption of calcium and interfere with the activation and metabolism of the vitamin, increasing the risk of bone loss. Doctors can measure levels of activated vitamin D (called 1,25 dihydroxycholecalciferol) to determine whether a deficiency exists; if so, activated vitamin D is only available by prescription. A study of rheumatoid arthritis patients treated with low amounts of prednisone found that those who received 1,000 mg of calcium per day plus 500 IU of vitamin D per day for two years experienced no bone loss during that time period. An analysis of properly conducted trials concluded that supplementation with vitamin D and calcium was more effective than placebo or calcium alone in protecting against corticosteroid-induced osteoporosis. Most doctors recommend 1,000 mg of calcium and 400–800 IU vitamin D per day for the prevention of osteoporosis.

  • Carbamazepine

    Though research results vary, long-term use of anticonvulsant drugs appears to interfere with vitamin D activity, which might lead to softening of bones (osteomalacia). One study showed that blood levels of vitamin D in males taking anticonvulsants were lower than those found in men who were not taking seizure medication. In a controlled study, bone strength improved in children taking anticonvulsant drugs who were supplemented with the activated form of vitamin D and 500 mg per day of calcium for nine months. Some research suggests that differences in exposure to sunlight—which normally increases blood levels of vitamin D—might explain why some studies have failed to find a beneficial effect of vitamin D supplementation. In one controlled study, blood vitamin D levels in children taking anticonvulsants were dramatically lower in winter months than in summer months. Another study of 450 people in Florida taking anticonvulsants found that few had drug-induced bone disease. Consequently, people taking anticonvulsant drugs who do not receive adequate sunlight should supplement with 400 IU of vitamin D each day to help prevent osteomalacia.

  • Cortisone

    Oral corticosteroids reduce absorption of calcium and interfere with the activation and metabolism of the vitamin, increasing the risk of bone loss. Doctors can measure levels of activated vitamin D (called 1,25 dihydroxycholecalciferol) to determine whether a deficiency exists; if so, activated vitamin D is only available by prescription. A study of rheumatoid arthritis patients treated with low amounts of prednisone found that those who received 1,000 mg of calcium per day plus 500 IU of vitamin D per day for two years experienced no bone loss during that time period. An analysis of properly conducted trials concluded that supplementation with vitamin D and calcium was more effective than placebo or calcium alone in protecting against corticosteroid-induced osteoporosis. Most doctors recommend 1,000 mg of calcium and 400–800 IU vitamin D per day for the prevention of osteoporosis.

  • Dexamethasone

    Oral corticosteroids reduce absorption of calcium and interfere with the activation and metabolism of the vitamin, increasing the risk of bone loss. Doctors can measure levels of activated vitamin D (called 1,25 dihydroxycholecalciferol) to determine whether a deficiency exists; if so, activated vitamin D is only available by prescription. A study of rheumatoid arthritis patients treated with low amounts of prednisone found that those who received 1,000 mg of calcium per day plus 500 IU of vitamin D per day for two years experienced no bone loss during that time period. An analysis of properly conducted trials concluded that supplementation with vitamin D and calcium was more effective than placebo or calcium alone in protecting against corticosteroid-induced osteoporosis. Most doctors recommend 1,000 mg of calcium and 400–800 IU vitamin D per day for the prevention of osteoporosis.

  • Dexamethasone Sod Phosphate-PF

    Oral corticosteroids reduce absorption of calcium and interfere with the activation and metabolism of the vitamin, increasing the risk of bone loss. Doctors can measure levels of activated vitamin D (called 1,25 dihydroxycholecalciferol) to determine whether a deficiency exists; if so, activated vitamin D is only available by prescription. A study of rheumatoid arthritis patients treated with low amounts of prednisone found that those who received 1,000 mg of calcium per day plus 500 IU of vitamin D per day for two years experienced no bone loss during that time period. An analysis of properly conducted trials concluded that supplementation with vitamin D and calcium was more effective than placebo or calcium alone in protecting against corticosteroid-induced osteoporosis. Most doctors recommend 1,000 mg of calcium and 400–800 IU vitamin D per day for the prevention of osteoporosis.

  • Dexamethasone Sodium Phosphate

    Oral corticosteroids reduce absorption of calcium and interfere with the activation and metabolism of the vitamin, increasing the risk of bone loss. Doctors can measure levels of activated vitamin D (called 1,25 dihydroxycholecalciferol) to determine whether a deficiency exists; if so, activated vitamin D is only available by prescription. A study of rheumatoid arthritis patients treated with low amounts of prednisone found that those who received 1,000 mg of calcium per day plus 500 IU of vitamin D per day for two years experienced no bone loss during that time period. An analysis of properly conducted trials concluded that supplementation with vitamin D and calcium was more effective than placebo or calcium alone in protecting against corticosteroid-induced osteoporosis. Most doctors recommend 1,000 mg of calcium and 400–800 IU vitamin D per day for the prevention of osteoporosis.

  • Felbamate

    Though research results vary, long-term use of anticonvulsant drugs appears to interfere with vitamin D activity, which might lead to softening of bones (osteomalacia). One study showed that blood levels of vitamin D in males taking anticonvulsants were lower than those found in men who were not taking seizure medication. In a controlled study, bone strength improved in children taking anticonvulsant drugs who were supplemented with the activated form of vitamin D and 500 mg per day of calcium for nine months. Some research suggests that differences in exposure to sunlight—which normally increases blood levels of vitamin D—might explain why some studies have failed to find a beneficial effect of vitamin D supplementation. In one controlled study, blood vitamin D levels in children taking anticonvulsants were dramatically lower in winter months than in summer months. Another study of 450 people in Florida taking anticonvulsants found that few had drug-induced bone disease. Consequently, people taking anticonvulsant drugs who do not receive adequate sunlight should supplement with 400 IU of vitamin D each day to help prevent osteomalacia.

  • Fluvastatin
    In a preliminary trial, supplementation with vitamin D appeared to prevent muscle-related side effects in patients taking statin drugs. The amount of vitamin D used in this study was very large (up to 50,000 IU twice a week) and potentially toxic. People taking statin drugs should consult with their doctor regarding how much vitamin D can be taken.
  • Hydrocortisone

    Oral corticosteroids reduce absorption of calcium and interfere with the activation and metabolism of the vitamin, increasing the risk of bone loss. Doctors can measure levels of activated vitamin D (called 1,25 dihydroxycholecalciferol) to determine whether a deficiency exists; if so, activated vitamin D is only available by prescription. A study of rheumatoid arthritis patients treated with low amounts of prednisone found that those who received 1,000 mg of calcium per day plus 500 IU of vitamin D per day for two years experienced no bone loss during that time period. An analysis of properly conducted trials concluded that supplementation with vitamin D and calcium was more effective than placebo or calcium alone in protecting against corticosteroid-induced osteoporosis. Most doctors recommend 1,000 mg of calcium and 400–800 IU vitamin D per day for the prevention of osteoporosis.

  • Hydrocortisone Acetate

    Oral corticosteroids reduce absorption of calcium and interfere with the activation and metabolism of the vitamin, increasing the risk of bone loss. Doctors can measure levels of activated vitamin D (called 1,25 dihydroxycholecalciferol) to determine whether a deficiency exists; if so, activated vitamin D is only available by prescription. A study of rheumatoid arthritis patients treated with low amounts of prednisone found that those who received 1,000 mg of calcium per day plus 500 IU of vitamin D per day for two years experienced no bone loss during that time period. An analysis of properly conducted trials concluded that supplementation with vitamin D and calcium was more effective than placebo or calcium alone in protecting against corticosteroid-induced osteoporosis. Most doctors recommend 1,000 mg of calcium and 400–800 IU vitamin D per day for the prevention of osteoporosis.

  • Hydrocortisone Sod Succinate

    Oral corticosteroids reduce absorption of calcium and interfere with the activation and metabolism of the vitamin, increasing the risk of bone loss. Doctors can measure levels of activated vitamin D (called 1,25 dihydroxycholecalciferol) to determine whether a deficiency exists; if so, activated vitamin D is only available by prescription. A study of rheumatoid arthritis patients treated with low amounts of prednisone found that those who received 1,000 mg of calcium per day plus 500 IU of vitamin D per day for two years experienced no bone loss during that time period. An analysis of properly conducted trials concluded that supplementation with vitamin D and calcium was more effective than placebo or calcium alone in protecting against corticosteroid-induced osteoporosis. Most doctors recommend 1,000 mg of calcium and 400–800 IU vitamin D per day for the prevention of osteoporosis.

  • Hydromorphone

    Oral corticosteroids reduce absorption of calcium and interfere with the activation and metabolism of the vitamin, increasing the risk of bone loss. Doctors can measure levels of activated vitamin D (called 1,25 dihydroxycholecalciferol) to determine whether a deficiency exists; if so, activated vitamin D is only available by prescription. A study of rheumatoid arthritis patients treated with low amounts of prednisone found that those who received 1,000 mg of calcium per day plus 500 IU of vitamin D per day for two years experienced no bone loss during that time period. An analysis of properly conducted trials concluded that supplementation with vitamin D and calcium was more effective than placebo or calcium alone in protecting against corticosteroid-induced osteoporosis. Most doctors recommend 1,000 mg of calcium and 400–800 IU vitamin D per day for the prevention of osteoporosis.

  • Levetiracetam

    Though research results vary, long-term use of anticonvulsant drugs appears to interfere with vitamin D activity, which might lead to softening of bones (osteomalacia). One study showed that blood levels of vitamin D in males taking anticonvulsants were lower than those found in men who were not taking seizure medication. In a controlled study, bone strength improved in children taking anticonvulsant drugs who were supplemented with the activated form of vitamin D and 500 mg per day of calcium for nine months. Some research suggests that differences in exposure to sunlight—which normally increases blood levels of vitamin D—might explain why some studies have failed to find a beneficial effect of vitamin D supplementation. In one controlled study, blood vitamin D levels in children taking anticonvulsants were dramatically lower in winter months than in summer months. Another study of 450 people in Florida taking anticonvulsants found that few had drug-induced bone disease. Consequently, people taking anticonvulsant drugs who do not receive adequate sunlight should supplement with 400 IU of vitamin D each day to help prevent osteomalacia.

  • Lovastatin
    In a preliminary trial, supplementation with vitamin D appeared to prevent muscle-related side effects in patients taking statin drugs. The amount of vitamin D used in this study was very large (up to 50,000 IU twice a week) and potentially toxic. People taking statin drugs should consult with their doctor regarding how much vitamin D can be taken.
  • Methylprednisolone

    Oral corticosteroids reduce absorption of calcium and interfere with the activation and metabolism of the vitamin, increasing the risk of bone loss. Doctors can measure levels of activated vitamin D (called 1,25 dihydroxycholecalciferol) to determine whether a deficiency exists; if so, activated vitamin D is only available by prescription. A study of rheumatoid arthritis patients treated with low amounts of prednisone found that those who received 1,000 mg of calcium per day plus 500 IU of vitamin D per day for two years experienced no bone loss during that time period. An analysis of properly conducted trials concluded that supplementation with vitamin D and calcium was more effective than placebo or calcium alone in protecting against corticosteroid-induced osteoporosis. Most doctors recommend 1,000 mg of calcium and 400–800 IU vitamin D per day for the prevention of osteoporosis.

  • Methylprednisolone Acetate

    Oral corticosteroids reduce absorption of calcium and interfere with the activation and metabolism of the vitamin, increasing the risk of bone loss. Doctors can measure levels of activated vitamin D (called 1,25 dihydroxycholecalciferol) to determine whether a deficiency exists; if so, activated vitamin D is only available by prescription. A study of rheumatoid arthritis patients treated with low amounts of prednisone found that those who received 1,000 mg of calcium per day plus 500 IU of vitamin D per day for two years experienced no bone loss during that time period. An analysis of properly conducted trials concluded that supplementation with vitamin D and calcium was more effective than placebo or calcium alone in protecting against corticosteroid-induced osteoporosis. Most doctors recommend 1,000 mg of calcium and 400–800 IU vitamin D per day for the prevention of osteoporosis.

  • Methylprednisolone Sodium Succ

    Oral corticosteroids reduce absorption of calcium and interfere with the activation and metabolism of the vitamin, increasing the risk of bone loss. Doctors can measure levels of activated vitamin D (called 1,25 dihydroxycholecalciferol) to determine whether a deficiency exists; if so, activated vitamin D is only available by prescription. A study of rheumatoid arthritis patients treated with low amounts of prednisone found that those who received 1,000 mg of calcium per day plus 500 IU of vitamin D per day for two years experienced no bone loss during that time period. An analysis of properly conducted trials concluded that supplementation with vitamin D and calcium was more effective than placebo or calcium alone in protecting against corticosteroid-induced osteoporosis. Most doctors recommend 1,000 mg of calcium and 400–800 IU vitamin D per day for the prevention of osteoporosis.

  • Oxcarbazepine

    Though research results vary, long-term use of anticonvulsant drugs appears to interfere with vitamin D activity, which might lead to softening of bones (osteomalacia). One study showed that blood levels of vitamin D in males taking anticonvulsants were lower than those found in men who were not taking seizure medication. In a controlled study, bone strength improved in children taking anticonvulsant drugs who were supplemented with the activated form of vitamin D and 500 mg per day of calcium for nine months. Some research suggests that differences in exposure to sunlight—which normally increases blood levels of vitamin D—might explain why some studies have failed to find a beneficial effect of vitamin D supplementation. In one controlled study, blood vitamin D levels in children taking anticonvulsants were dramatically lower in winter months than in summer months. Another study of 450 people in Florida taking anticonvulsants found that few had drug-induced bone disease. Consequently, people taking anticonvulsant drugs who do not receive adequate sunlight should supplement with 400 IU of vitamin D each day to help prevent osteomalacia.

  • Pitavastatin
    In a preliminary trial, supplementation with vitamin D appeared to prevent muscle-related side effects in patients taking statin drugs. The amount of vitamin D used in this study was very large (up to 50,000 IU twice a week) and potentially toxic. People taking statin drugs should consult with their doctor regarding how much vitamin D can be taken.
  • Pravastatin
    In a preliminary trial, supplementation with vitamin D appeared to prevent muscle-related side effects in patients taking statin drugs. The amount of vitamin D used in this study was very large (up to 50,000 IU twice a week) and potentially toxic. People taking statin drugs should consult with their doctor regarding how much vitamin D can be taken.
  • Prednisolone

    Oral corticosteroids reduce absorption of calcium and interfere with the activation and metabolism of the vitamin, increasing the risk of bone loss. Doctors can measure levels of activated vitamin D (called 1,25 dihydroxycholecalciferol) to determine whether a deficiency exists; if so, activated vitamin D is only available by prescription. A study of rheumatoid arthritis patients treated with low amounts of prednisone found that those who received 1,000 mg of calcium per day plus 500 IU of vitamin D per day for two years experienced no bone loss during that time period. An analysis of properly conducted trials concluded that supplementation with vitamin D and calcium was more effective than placebo or calcium alone in protecting against corticosteroid-induced osteoporosis. Most doctors recommend 1,000 mg of calcium and 400–800 IU vitamin D per day for the prevention of osteoporosis.

  • Prednisolone Acetate

    Oral corticosteroids reduce absorption of calcium and interfere with the activation and metabolism of the vitamin, increasing the risk of bone loss. Doctors can measure levels of activated vitamin D (called 1,25 dihydroxycholecalciferol) to determine whether a deficiency exists; if so, activated vitamin D is only available by prescription. A study of rheumatoid arthritis patients treated with low amounts of prednisone found that those who received 1,000 mg of calcium per day plus 500 IU of vitamin D per day for two years experienced no bone loss during that time period. An analysis of properly conducted trials concluded that supplementation with vitamin D and calcium was more effective than placebo or calcium alone in protecting against corticosteroid-induced osteoporosis. Most doctors recommend 1,000 mg of calcium and 400–800 IU vitamin D per day for the prevention of osteoporosis.

  • Prednisolone Sodium Phosphate

    Oral corticosteroids reduce absorption of calcium and interfere with the activation and metabolism of the vitamin, increasing the risk of bone loss. Doctors can measure levels of activated vitamin D (called 1,25 dihydroxycholecalciferol) to determine whether a deficiency exists; if so, activated vitamin D is only available by prescription. A study of rheumatoid arthritis patients treated with low amounts of prednisone found that those who received 1,000 mg of calcium per day plus 500 IU of vitamin D per day for two years experienced no bone loss during that time period. An analysis of properly conducted trials concluded that supplementation with vitamin D and calcium was more effective than placebo or calcium alone in protecting against corticosteroid-induced osteoporosis. Most doctors recommend 1,000 mg of calcium and 400–800 IU vitamin D per day for the prevention of osteoporosis.

  • Prednisone

    Oral corticosteroids reduce absorption of calcium and interfere with the activation and metabolism of the vitamin, increasing the risk of bone loss. Doctors can measure levels of activated vitamin D (called 1,25 dihydroxycholecalciferol) to determine whether a deficiency exists; if so, activated vitamin D is only available by prescription. A study of rheumatoid arthritis patients treated with low amounts of prednisone found that those who received 1,000 mg of calcium per day plus 500 IU of vitamin D per day for two years experienced no bone loss during that time period. An analysis of properly conducted trials concluded that supplementation with vitamin D and calcium was more effective than placebo or calcium alone in protecting against corticosteroid-induced osteoporosis. Most doctors recommend 1,000 mg of calcium and 400–800 IU vitamin D per day for the prevention of osteoporosis.

  • Primidone

    Though research results vary, long-term use of anticonvulsant drugs appears to interfere with vitamin D activity, which might lead to softening of bones (osteomalacia). One study showed that blood levels of vitamin D in males taking anticonvulsants were lower than those found in men who were not taking seizure medication. In a controlled study, bone strength improved in children taking anticonvulsant drugs who were supplemented with the activated form of vitamin D and 500 mg per day of calcium for nine months. Some research suggests that differences in exposure to sunlight—which normally increases blood levels of vitamin D—might explain why some studies have failed to find a beneficial effect of vitamin D supplementation. In one controlled study, blood vitamin D levels in children taking anticonvulsants were dramatically lower in winter months than in summer months. Another study of 450 people in Florida taking anticonvulsants found that few had drug-induced bone disease. Consequently, people taking anticonvulsant drugs who do not receive adequate sunlight should supplement with 400 IU of vitamin D each day to help prevent osteomalacia.

  • Rosuvastatin
    In a preliminary trial, supplementation with vitamin D appeared to prevent muscle-related side effects in patients taking statin drugs. The amount of vitamin D used in this study was very large (up to 50,000 IU twice a week) and potentially toxic. People taking statin drugs should consult with their doctor regarding how much vitamin D can be taken.
  • Simvastatin
    In a preliminary trial, supplementation with vitamin D appeared to prevent muscle-related side effects in patients taking statin drugs. The amount of vitamin D used in this study was very large (up to 50,000 IU twice a week) and potentially toxic. People taking statin drugs should consult with their doctor regarding how much vitamin D can be taken.
  • Topiramate

    Though research results vary, long-term use of anticonvulsant drugs appears to interfere with vitamin D activity, which might lead to softening of bones (osteomalacia). One study showed that blood levels of vitamin D in males taking anticonvulsants were lower than those found in men who were not taking seizure medication. In a controlled study, bone strength improved in children taking anticonvulsant drugs who were supplemented with the activated form of vitamin D and 500 mg per day of calcium for nine months. Some research suggests that differences in exposure to sunlight—which normally increases blood levels of vitamin D—might explain why some studies have failed to find a beneficial effect of vitamin D supplementation. In one controlled study, blood vitamin D levels in children taking anticonvulsants were dramatically lower in winter months than in summer months. Another study of 450 people in Florida taking anticonvulsants found that few had drug-induced bone disease. Consequently, people taking anticonvulsant drugs who do not receive adequate sunlight should supplement with 400 IU of vitamin D each day to help prevent osteomalacia.

  • Triamcinolone

    Oral corticosteroids reduce absorption of calcium and interfere with the activation and metabolism of the vitamin, increasing the risk of bone loss. Doctors can measure levels of activated vitamin D (called 1,25 dihydroxycholecalciferol) to determine whether a deficiency exists; if so, activated vitamin D is only available by prescription. A study of rheumatoid arthritis patients treated with low amounts of prednisone found that those who received 1,000 mg of calcium per day plus 500 IU of vitamin D per day for two years experienced no bone loss during that time period. An analysis of properly conducted trials concluded that supplementation with vitamin D and calcium was more effective than placebo or calcium alone in protecting against corticosteroid-induced osteoporosis. Most doctors recommend 1,000 mg of calcium and 400–800 IU vitamin D per day for the prevention of osteoporosis.

  • Zoledronic Acid
    Musculoskeletal pain is one of the side effects of zoledronic acid. In a double-blind trial, supplementation with a single dose of vitamin D (300,000 IU) significantly decreased the severity of musculoskeletal pain in women being treated with zoledronic acid. The large amount of vitamin D used in this study has the potential to cause adverse effects, and therefore should be taken only under medical supervision.
  • Zonisamide

    Though research results vary, long-term use of anticonvulsant drugs appears to interfere with vitamin D activity, which might lead to softening of bones (osteomalacia). One study showed that blood levels of vitamin D in males taking anticonvulsants were lower than those found in men who were not taking seizure medication. In a controlled study, bone strength improved in children taking anticonvulsant drugs who were supplemented with the activated form of vitamin D and 500 mg per day of calcium for nine months. Some research suggests that differences in exposure to sunlight—which normally increases blood levels of vitamin D—might explain why some studies have failed to find a beneficial effect of vitamin D supplementation. In one controlled study, blood vitamin D levels in children taking anticonvulsants were dramatically lower in winter months than in summer months. Another study of 450 people in Florida taking anticonvulsants found that few had drug-induced bone disease. Consequently, people taking anticonvulsant drugs who do not receive adequate sunlight should supplement with 400 IU of vitamin D each day to help prevent osteomalacia.

Support Medicine

  • Estradiol

    In controlled studies, the addition of 300 IU per day of vitamin D3 (cholecalciferol) did not improve the bone-preserving or fracture-preventing effects of hormone replacement with estradiol plus a progestin (a synthetic form of progesterone) in postmenopausal women without osteoporosis. However, in a controlled study of osteoporotic women, only those receiving both hormone replacement and vitamin D had increases in bone density of the hip; no improvement occurred in the hip with hormones alone. More research is needed to determine conclusively when vitamin D is important to add to hormone replacement.

  • Sodium Fluoride

    Collagen is a protein that is used in many areas of the body for structural support. One test tube study showed that the active form of vitamin D, 1,25 dihydroxycholecalciferol, increased the production of a certain type of collagen when it was combined with fluoride. Controlled research is needed to determine whether taking 1,25 dihydroxycholecalciferol with sodium fluoride might promote beneficial collagen growth.

Reduces Effectiveness

  • none

Potential Negative Interaction

  • Verapamil

    Vitamin D may interfere with the effectiveness of verapamil. People taking verapamil should ask their doctor before using vitamin D-containing supplements.

  • Warfarin

    In 1975, a single letter to the Journal of the American Medical Association suggested that vitamin D increases the activity of anticoagulants and that this interaction could prove dangerous. However, there have been no other reports of such an interaction, even though tens of millions of people are taking multivitamins that contain vitamin D. Most doctors typically do not tell patients taking anticoagulant medications to avoid vitamin D.

Explanation Required

  • Allopurinol

    Individuals with gout have low blood concentration of the active form of vitamin D (1,25 dihydroxycholecalciferol), and allopurinol corrects this problem.

  • Bendroflumethiazide

    The reduction in urinary calcium loss resulting from treatment with thiazide diuretics is due primarily to changes in kidney function and may also be due, in part, to changes in vitamin D metabolism. However, there is no evidence to suggest that people taking diuretics have different requirements for vitamin D.

  • Chlorothiazide

    The reduction in urinary calcium loss resulting from treatment with thiazide diuretics is due primarily to changes in kidney function and may also be due, in part, to changes in vitamin D metabolism. However, there is no evidence to suggest that people taking diuretics have different requirements for vitamin D.

  • Chlorthalidone

    The reduction in urinary calcium loss resulting from treatment with thiazide diuretics is due primarily to changes in kidney function and may also be due, in part, to changes in vitamin D metabolism. However, there is no evidence to suggest that people taking diuretics have different requirements for vitamin D.

  • Gabapentin

    Though research results vary, long-term use of anticonvulsant drugs appears to interfere with vitamin D activity, which might lead to softening of bones (osteomalacia). One study showed that blood levels of vitamin D in males taking anticonvulsants were lower than those found in men who were not taking seizure medication. In a controlled study, bone strength improved in children taking anticonvulsant drugs who were supplemented with the activated form of vitamin D and 500 mg per day of calcium for nine months. Some research suggests that differences in exposure to sunlight—which normally increases blood levels of vitamin D—might explain why some studies have failed to find a beneficial effect of vitamin D supplementation. In one controlled study, blood vitamin D levels in children taking anticonvulsants were dramatically lower in winter months than in summer months. Another study of 450 people in Florida taking anticonvulsants found that few had drug-induced bone disease. Consequently, people taking anticonvulsant drugs who do not receive adequate sunlight should supplement with 400 IU of vitamin D each day to help prevent osteomalacia.

  • Hydrochlorothiazide

    The reduction in urinary calcium loss resulting from treatment with thiazide diuretics is due primarily to changes in kidney function and may also be due, in part, to changes in vitamin D metabolism. However, there is no evidence to suggest that people taking diuretics have different requirements for vitamin D.

  • Hydroflumethiazide

    The reduction in urinary calcium loss resulting from treatment with thiazide diuretics is due primarily to changes in kidney function and may also be due, in part, to changes in vitamin D metabolism. However, there is no evidence to suggest that people taking diuretics have different requirements for vitamin D.

  • Medroxyprogesterone

    In a study of postmenopausal women, treatment with estrogen alone increased vitamin D blood levels, whereas estrogen plus medroxyprogesterone lowered vitamin D back to the level seen without estrogen use. This outcome might suggest that medroxyprogesterone interferes with beneficial effects estrogen may have on vitamin D metabolism and vitamin D supplementation would be called for. However, some research has not found the addition of vitamin D to estrogen/progestin combinations to be helpful. Therefore, while many doctors recommend 400 IU vitamin D to women taking estrogen/progestin combination hormone products, the efficacy of such supplementation has not been proven.

  • Methyclothiazide

    The reduction in urinary calcium loss resulting from treatment with thiazide diuretics is due primarily to changes in kidney function and may also be due, in part, to changes in vitamin D metabolism. However, there is no evidence to suggest that people taking diuretics have different requirements for vitamin D.

  • Metolazone

    The reduction in urinary calcium loss resulting from treatment with thiazide diuretics is due primarily to changes in kidney function and may also be due, in part, to changes in vitamin D metabolism.10 However, there is no evidence to suggest that people taking diuretics have different requirements for vitamin D.

  • Polythiazide

    The reduction in urinary calcium loss resulting from treatment with thiazide diuretics is due primarily to changes in kidney function and may also be due, in part, to changes in vitamin D metabolism. However, there is no evidence to suggest that people taking diuretics have different requirements for vitamin D.

  • Risedronate

    Short-term treatment with risedronate in people with hyperparathydoidism—a disorder characterized by high blood levels of calcium—resulted in lower calcium blood levels. Additional research is needed to determine whether people taking risedronate for Paget’s disease might develop low blood calcium levels. As a precaution, people with Paget’s disease should take supplemental calcium and vitamin D if dietary intake is inadequate. However, taking risedronate at the same time as calcium supplements reduces absorption of the drug. Therefore, people taking risedronate for Paget’s disease should take calcium supplements an hour before or two hours after taking the drug.

  • Trichlormethiazide

    The reduction in urinary calcium loss resulting from treatment with thiazide diuretics is due primarily to changes in kidney function and may also be due, in part, to changes in vitamin D metabolism. However, there is no evidence to suggest that people taking diuretics have different requirements for vitamin D.

  • Valproate

    Though research results vary, long-term use of anticonvulsant drugs appears to interfere with vitamin D activity, which might lead to softening of bones (osteomalacia). One study showed that blood levels of vitamin D in males taking anticonvulsants were lower than those found in men who were not taking seizure medication. In a controlled study, bone strength improved in children taking anticonvulsant drugs who were supplemented with the activated form of vitamin D and 500 mg per day of calcium for nine months. Some research suggests that differences in exposure to sunlight—which normally increases blood levels of vitamin D—might explain why some studies have failed to find a beneficial effect of vitamin D supplementation. In one controlled study, blood vitamin D levels in children taking anticonvulsants were dramatically lower in winter months than in summer months. Another study of 450 people in Florida taking anticonvulsants found that few had drug-induced bone disease. Consequently, people taking anticonvulsant drugs who do not receive adequate sunlight should supplement with 400 IU of vitamin D each day to help prevent osteomalacia.

The Drug-Nutrient Interactions table may not include every possible interaction. Taking medicines with meals, on an empty stomach, or with alcohol may influence their effects. For details, refer to the manufacturers’ package information as these are not covered in this table. If you take medications, always discuss the potential risks and benefits of adding a supplement with your doctor or pharmacist.

Side Effects

Side Effects

People with hyperparathyroidism should not take vitamin D without consulting a physician. People with sarcoidosis should not supplement with vitamin D, unless a doctor has determined that their calcium levels are not elevated. Too much vitamin D taken for long periods of time may lead to headaches, weight loss, and kidney stones. Rarely, excessive vitamin D may even lead to deafness, blindness, increased thirst, increased urination, diarrhea, irritability, children’s failure to gain weight, or death.

Most people take 400 IU per day, a safe amount for adults. Some researchers believe that amounts up to 10,000 IU per day are safe for the average healthy adult, although adverse effects may occur even at lower levels among people with hypersensitivity to vitamin D (e.g. hyperparathyroidism).20 In fact, of all published cases of vitamin D toxicity for which a vitamin D amount is known, only one occurred at a level of intake under 40,000 IU per day.21 Nevertheless, people wishing to take more than 1,000 IU per day for long periods of time should consult a physician. People should remember the total daily intake of vitamin D includes vitamin D from fortified milk and other fortified foods, cod liver oil, supplements that contain vitamin D, and sunlight. People who receive adequate sunlight exposure do not need as much vitamin D in their diet as do people who receive minimal sunlight exposure.

Some,22 but not all,23 research suggests that vitamin D may slightly raise blood levels of cholesterol in humans.

References

1. Dawson-Hughes B, Harris SS, Krall EA, Dallal GE. Effect of calcium and vitamin D supplementation on bone density in men and women 65 years of age or older. N Engl J Med 1997;337:670-6.

2. Dawson-Hughes B. Calcium and vitamin D nutritional needs of elderly women. J Nutr 1996;126(4 Suppl):1165-7S.

3. Chapuy MC, Arlot ME, Duboeuf F, et al. Vitamin D3 and calcium to prevent hip fractures in the elderly women. N Engl J Med 1992;327:1637-42.

4. Dawson-Hughes B, Harris SS, Krall EA, et al. Rates of bone loss in postmenopausal women randomly assigned to one of two dosages of vitamin D. Am J Clin Nutr 1995;61:1140-5.

5. Glerup H, Mikkelsen K, Poulsen L, et al. Commonly recommended daily intake of vitamin D is not sufficient if sunlight exposure is limited. J Intern Med 2000;247:260-8.

6. Bischoff-Ferrari HA, Giovannucci E, Willett WC, et al. Estimation of optimal serum concentrations of 25-hydroxyvitamin D for multiple health outcomes. Am J Clin Nutr 2006;84:18-28.

7. Moreira-Pfrimer LDF, Pedrosa MAC, Teixeira L, Lazaretti-Castro M. Treatment of vitamin D deficiency increases lower limb muscle strength in institutionalized older people independently of regular physical activity: a randomized double-blind controlled trial. Ann Nutr Metab 2009;54:291-300.

8. Agarwal KS, Mughal MZ, Upadhyay P, et al. The impact of atmospheric pollution on vitamin D status of infants and toddlers in Delhi, India. Arch Dis Child 2002;87:111-3.

9. Manicourt DH, Devogelaer JP. Urban tropospheric ozone increases the prevalence of vitamin D deficiency among Belgian postmenopausal women with outdoor activities during summer. J Clin Endocrinol Metab 2008;93:3893-9.

10. Kyriakidou-Himonas M, Aloia JF, Yeh JK. Vitamin D supplementation in postmenopausal black women. J Clin Endocrinol Metab 1999;84:3988-90.

11. Basha B, Rao S, Han ZH, Parfitt, AM. Osteomalacia due to vitamin D depletion: neglected consequence of intestinal malabsorption. Am J Med 2000;108(4):296-300.

12. Yamashita H, Noguchi S, Takatsu K, et al. High prevalence of vitamin D deficiency in Japanese female patients with Graves' disease. Endocr J 2001;48(6):63-9.

13. Silverberg SL, Shane E, Dempster DW, Bilezikian JP. The effects of vitamin D insufficiency in patients with primary hyperparathyroidism. Am J Med 1999; 107:561-7.

14. Van Veldhuizen PJ, Taylor SA, Williamson S, Drees BM. Treatment of vitamin D deficiency in patients with metastatic prostate cancer may improve bone pain and muscle strength. J Urol 2000;163:187-90.

15. Chapuy MC, Preziosi P, Maamer M, et al. Prevalence of vitamin D insufficiency in an adult normal population. Osteoporos Int 1997;7:439-43.

16. Thomas MK, Lloyd-Jones DM, Thadhani RI, et al. Hypovitaminosis D in medical inpatients. N Engl J Med 1998;338:777-83.

17. Harris SS, Dawson-Hughes B, Perrone GA. Plasma 25-hydroxyvitamin D responses of younger and older men to three weeks of supplementation with 1800 IU/day of vitamin D. J Am Coll Nutr 1999;18:470-4.

18. Gaby, AR. Nutritional Medicine. Concord, NH: Friz Perlberg Publishing, 2011.

19. Lind L, Skarfors E, Berglund L, et al. Serum calcium: a new, independent prospective risk factor for myocardial infarction in middle-aged men followed for 18 years. J Clin Epidemiol 1997;50:967-73.

20. Vieth R. Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safety. Am J Clin Nutr 1999;69:842-56.

21. Vieth R. Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safety. Am J Clin Nutr 1999;69:842-56.

22. Heikkinen AM, Tuppurainen MT, Komulainen M, et al. Long-term vitamin D3 supplementation may have adverse effects on serum lipids during postmenopausal hormone replacement therapy. Eur J Endocrinol 1997;137:495-502.

23. Scragg R, Khaw KT, Murphy S. Effect of winter oral vitamin D3 supplementation on cardiovascular risk factors in elderly adults. Eur J Clin Nutr 1995;49:640-6.

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Vitamin D