Your test results help your doctor follow what's happening with your infection and guide treatment choices. HIV viral load predicts how fast the disease will progress, while other tests, like the CD4 count, indicate how much damage the virus has already caused.
The test can also help diagnose recent HIV infection in someone with inconclusive HIV antibody tests. However, in theses cases, a subsequent positive HIV antibody test should be used to confirm the diagnosis.
Keeping your viral load low will make complications of HIV less likely and help you live longer. It is possible if you adhere to your treatment to obtain a normal, or near-normal life expectancy.
How It's Tested
HIV viral load tests look for RNA, the part of HIV that has the recipe for reproducing itself. They add an enzyme, a kind of protein, to make more copies of the RNA. This makes it easier to measure how much HIV is in your blood sample.
These RT-PCR (real-time polymerase chain reaction) tests are much more sensitive than HIV tests used in the past. They can find as few as 20 copies of HIV RNA in a milliliter of blood.
Your doctor should use the same HIV viral load test each time, because tests made by different manufacturers might give you slightly different results. If your viral load changes, you want to be confident it's from what's happening inside you, not skewed by the testing method.
Scientists are working on new, even more sensitive methods, too.
What the Results Mean
A high viral load is generally considered about 100,000 copies, but you could have 1 million or more. The virus is at work making copies of itself, and the disease may progress quickly.
A lower HIV viral load is below 10,000 copies. The virus probably isn't actively reproducing as fast, and damage to your immune system may be slowed, but this is not optimal.
A viral load that can't be detected -- less than 20 copies -- is always the goal of HIV treatment. This doesn't mean you're cured. Unfortunately, the virus is still able to survive in various cells in the body. But maintaining an undetectable viral load is compatible with a normal, or near-normal life span. Continuing to take your medicine as prescribed to keep the virus undetectable is very important.
When your HIV viral load is undetectable, there is little to no risk of infecting others, but most doctors still advise using condoms to prevent acquiring other strains of HIV and other sexually transmitted infections.
When to Get a Test
Right after you're diagnosed, you should get a viral load test for a "baseline measurement." That gives your doctor something to compare future test results to.
When you start or change medicine, a test every 2 to 8 weeks afterwards helps your doctor decide how well it's working. An effective drug combination can often drop the HIV viral load to one-tenth of what it was within a couple of months.
After that, you should get a test as often as your doctor recommends to see how your medications are controlling the virus. Within 6 months, the viral load should continue to drop to fewer than 20 copies. If your HIV seems to be under control, you can probably be tested less frequently.