Thiazide Diuretics


Thiazide Diuretics

Thiazide diuretics are a family of drugs that remove water from the body. They are referred to as potassium-depleting because they cause the body to lose potassium as well as water. Potassium-depleting diuretics also cause the body to lose magnesium. Thiazide diuretics are used to lower blood pressure in people with high blood pressure. Diuretics are also used to reduce water accumulation caused by other diseases.

Thiazide diuretics are also combined with other drugs to treat various conditions.

The information in this article pertains to thiazide diuretics in general. The interactions reported here may not apply to all the Also Indexed As terms. Talk to your doctor or pharmacist if you are taking any of these drugs.

At the time of writing, this product had no well-known interactions with food, supplements, or other compounds. Follow manufacturer instructions for safe use.

Interactions Details

Interactions with Vitamins


Thiazide diuretics decrease calcium loss in the urine due to actions on the kidneys.1 As a result, it may be less important for some people taking thiazide diuretics to supplement calcium than it is for other people.

Folic acid

One study showed that people taking diuretics for more than six months had dramatically lower blood levels of folic acid and higher levels of homocysteine compared with individuals not taking diuretics.2 Homocysteine, a toxic amino acid byproduct, has been associated with atherosclerosis. Until further information is available, people taking diuretics for longer than six months should probably supplement with folic acid.

Magnesium and Potassium

Potassium-depleting diuretics, including thiazide diuretics, cause the body to lose potassium; they may also cause cellular magnesium depletion,3 although this deficiency may not be reflected by a low blood level of magnesium.4 Magnesium loss induced by potassium-depleting diuretics can cause additional potassium loss. Until more is known, it has been suggested that people taking potassium-depleting diuretics, including thiazide diuretics, should supplement both potassium and magnesium.5

People taking thiazide diuretics should be monitored by their prescribing doctor, who will prescribe potassium supplements if needed. Such supplementation is particularly critical before surgery in patients with a history of heart disease. In a preliminary study, people with low blood levels of potassium (in part related to diuretic use) had a higher incidence of serious problems resulting from surgery (including death) compared with those having normal potassium levels.6 A double-blind trial showed that thiazide diuretic use led to a reduction in blood levels of potassium in some participants. Those experiencing decreased potassium levels were also more likely to experience cardiovascular events, such as heart attacks, stroke, heart failure, aneurysm, and sudden cardiac death.7Fruit is high in potassium, and increasing fruit intake (especially bananas) is another way of supplementing potassium.

Magnesium supplementation for people taking thiazide diuretics is typically 300–600 mg per day, though higher amounts (over 800 mg per day) have been reported in a controlled study to reduce side effects of thiazides.8 Combining supplementation of both potassium and magnesium has been reported to correct abnormally low blood levels of potassium and also to protect against excessive loss of magnesium.9

Vitamin D

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.


Thiazide diuretics can increase urinary zinc loss.11


Diuretics, including thiazide diuretics, cause increased loss of sodium in the urine. By removing sodium from the body, diuretics also cause water to leave the body. This reduction of body water is the purpose of taking diuretics. Therefore, there is usually no reason to replace lost sodium, although strict limitation of salt intake in combination with the actions of diuretics can sometimes cause excessive sodium depletion. On the other hand, people who restrict sodium intake, and in the process reduce blood pressure, may need to have their dose of diuretics lowered.

Interactions with Herbs

Herbs that have a diuretic effect should be avoided when taking diuretic medications, as they may enhance the effect of these drugs and lead to possible cardiovascular side effects. These herbs include dandelion, uva ursi, juniper, buchu, cleavers, horsetail, and gravel root.12

Alder Buckthorn , Buckthorn(Rhamnus catartica, Rhamnus frangula, Frangula alnus)

Use buckthorn or alder buckthorn for more than ten days consecutively may cause a loss of electrolytes (especially the mineral potassium). Medications that also cause potassium loss, such as some diuretics, should be used with caution when taking buckthorn or alder buckthorn.13

Digitalis (Digitalis purpurea)

Digitalis refers to a family of plants commonly called foxglove, which contains digitalis glycosides, chemicals with actions and toxicities similar to the prescription drug digoxin. Thiazide diuretics can increase the risk of digitalis-induced heart disturbances.14 Thiazide diuretics and digitalis-containing products should be used only under the direct supervision of a doctor trained in their use.

Ginkgo biloba

One case was reported in which ginkgo use was associated with high blood pressure in a person treated with a thiazide diuretic.15 Ginkgo was not proven to be the cause of this reaction.

Licorice  (Glycyrrhiza glabra)

Licorice may increase the side effects of potassium-depleting diuretics, including thiazide diuretics.16 Thiazide diuretics and licorice should be used together only under careful medical supervision. At the time of this writing, no evidence was found of interactions between deglycyrrhizinated licorice (DGL) and any diuretic was found in the medical literature.

Interactions with Foods & Other Compounds


Thiazide diuretics may be taken with food to avoid stomach upset.17


1. Threlkeld DS, ed. Diuretics and Cardiovasculars, Thiazides and Related Diuretics. In Facts and Comparisons Drug Information. St. Louis, MO: Facts and Comparisons, Jul 1993, 135a–7c.

2. Morrow LE, Grimsley EW. Long-term diuretic therapy in hypertensive patients: effects on serum homocysteine, vitamin B6, vitamin B12, and red blood cell folate concentrations. South Med J 1999;92:866–70.

3. Martin B, Milligan K. Diuretic-associated hypomagnesiumia in the elderly. Arch Intern Med 1987;147:1768–71.

4. Kroenke K, Wood DR, Hanley JF. The value of serum magnesium determination in hypertensive patients receiving diuretics. Arch Intern Med 1987;147:1553–6.

5. Whang R, Whang DD, Ryan MP. Refractory potassium repletion—a consequence of magnesium deficiency. Arch Intern Med 1992;152:40–5.

6. Wahr JA, Parks R, Boisvert D, et al. Preoperative serum potassium levels and perioperative outcomes in cardiac surgery patients. JAMA 1999;281:2203–10.

7. Franse LV, Pahor M, Di Bari M, et al. Hypokalemia associated with diuretic use and cardiovascular events in the Systolic Hypertension in the Elderly Program. Hypertension 2000;35:1025–30.

8. Ruml LA, Gonzalez G, Taylor R, et al. Effect of varying doses of potassium-magnesium citrate on thiazide-induced hypokalemia and magnesium loss. Am J Ther 1999;6:45–50.

9. Ruml LA, Pak CYO. Effect of potassium magnesium citrate on thiazide-induced hypokalemia and magnesium loss. Am J Kidney Dis 1999;34:107–13.

10. Riis B, Christiansen C. Actions of thiazide on vitamin D metabolism: A controlled therapeutic trial in normal women early in the postmenopause. Metabolism 1985;34:421–4.

11. Reyes AJ, Leary WP, Lockett CJ, et al. Diuretics and zinc. S Afr Med J 1982;62:373–5.

12. Brinker F. Herb Contraindications and Drug Interactions. Sandy, OR: Eclectic Institute, 1997, 102–3.

13. European Scientific Cooperative on Phytotherapy (ESCOP). Frangulae cortex, frangula bark. Monographs on the Medicinal Uses of Plant Drugs. Exeter, UK: University of Exeter, Centre for Complementary Health Studies, 1997.

14. Threlkeld DS, ed. Diuretics and Cardiovasculars, Thiazides and Related Diuretics. In Facts and Comparisons Drug Information. St. Louis, MO: Facts and Comparisons, Apr 1993, 135a–7c.

15. Shaw D et al. Traditional remedies and food supplements: a 5-year toxicological study (1991–1995). Drug Safety 1997;17:342–56.

16. Shintani S, Murase H, Tsukagoshi H, Shiigai T. Glycyrrhizin (licorice)-induced hypokalemic myopathy. Report of two cases and review of the literature. Eur Neurol 1992;32:44–51.

17. Threlkeld DS, ed. Diuretics and Cardiovasculars, Thiazides and Related Diuretics. In Facts and Comparisons Drug Information. St. Louis, MO: Facts and Comparisons, Jul 1993, 135a–7c.

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