Viral load is a measurement of how much HIV is present in your blood. A sample of blood is drawn and sent to a lab for testing. Results are expressed as the number of copies of the virus per milliliter of blood. Each virus is called a "copy" because HIV reproduces by making copies of itself (replicating).
The viral load test gives a more accurate picture than a CD4+ cell count of what the virus is doing in your body at the moment. (The CD4+ test measures the effect HIV is having on your immune system.) The viral load test is used to help decide when to change antiretroviral medicines.
Medical Review:E. Gregory Thompson MD - Internal Medicine & Adam Husney MD - Family Medicine & Peter Shalit MD, PhD - Internal Medicine