Viral Load

What is "viral load"?

The term “viral load” refers to the amount of HIV in a sample of your blood. When your viral load is high, you have more HIV in your body, and that means your immune system is not fighting HIV as well.

What is a Viral Load Test and Why is it Important?

A viral load test is a lab test that measures the number of HIV virus particles in a milliliter of your blood. These particles are called "copies."

A viral load test helps provide information on your health status and how well antiretroviral therapy (ART – treatment with HIV medicines) is controlling the virus.

ART involves taking a combination of HIV medicines (called an HIV regimen) every day. ART can’t cure HIV, but it can help you live a longer, healthier life and reduce your risk of HIV transmission.

The goal of ART is to move your viral load down, ideally to undetectable levels. In general, your viral load will be declared "undetectable" if it is under 40 to 75 copies in a sample of your blood. The exact number depends on the lab that analyzes your test.

Having an “undetectable” viral load doesn’t mean that the virus is completely gone from your body, just that it is below what a lab test can find. You still have HIV and need to stay on ART to remain healthy.

What is a Normal Viral Load?

There is really no such thing as a “normal” viral load. People who aren’t infected with HIV have no viral load at all, so there’s no “normal” range for reference, as there is for many other HIV lab tests (such as CD4 counts.)

When and How Often do I Need a Viral Load Test?

Your HIV care provider will order a viral load test at your first visit to determine your viral load. A viral load test will:

• Show how well your HIV treatment is controlling the virus, and
• Provide health information on your health status.

After that, you should have a viral load test every 3 to 6 months before you start taking a new HIV medicine, and 2 to 8 weeks after starting or changing HIV medicines until your viral load is suppressed.  For more information, see the HIV treatment guidelines regarding laboratory testing.

Can I transmit HIV if I Have an Undetectable Viral Load?

As noted above, the goal of ART is to reduce your viral load, ideally to an undetectable level. If your viral load goes down after starting ART, the treatment is working.

Having an undetectable viral load greatly lowers your chance of transmitting the virus to your sexual and drug-using partners who are HIV-negative. However, even when your viral load is undetectable, HIV can still exist in semen, vaginal and rectal fluids, breast milk, and other parts of your body. For this reason, you should continue to take steps to prevent HIV transmission. For example:

1. HIV may still be found in your genital fluids (semen or vaginal fluids). The viral load test only measures the amount of HIV in your blood. Although ART also lowers viral load in genital fluids, HIV can sometimes be present in your genital fluids even when it is undetectable in your blood.
2. Your viral load may go up between tests. When this happens, you may be more likely to transmit HIV to your partner(s). Your viral load may go up without you knowing it because you may not feel any different.
3. Sexually transmitted diseases (STDs) can increase your viral load in your genital fluids. This means that if you are living with HIV and also have an STD, you may be able to transmit HIV to your partner(s) even if your viral load is undetectable.

Researchers are studying how much you can lower your chances of transmitting HIV when your viral load is undetectable. One large multinational study indicates that ART that consistently suppresses HIV is highly effective at preventing sexual transmission of the virus in heterosexual couples where one person is HIV-infected and the other is not. In fact, that study found that ARTreduces the risk of heterosexual HIV transmission by 93% or more if viral suppression is achieved and maintained. Researchers did not observe any HIV transmission during this study when the HIV-infected partner’s virus was stably suppressed by ART. (Read more about these NIH-supported study findings released in the summer of 2015.)

If you are taking ART, follow your HIV care provider’s advice. Visit your HIV care provider regularly and always take your HIV meds as directed. This will give you the greatest chance of having an undetectable viral load. Taking other actions, like using a condom consistently and correctly, can lower your chances of transmitting HIV or contracting an STD even more. For more information, see Lower Your Sexual Risk of HIV.