The Power of Undetectable: What you need to know about HIV treatment as prevention

Treatment as Prevention

We now know that medications that treat HIV can also prevent HIV transmission: If you are HIV-positive and take HIV treatment that suppresses your virus to undetectable levels (you have an undetectable viral load), you will not pass HIV to the people you have sex with. In other words, undetectable HIV is sexually untransmittable.

Effective treatment can also prevent HIV transmission to a baby during pregnancy and birth, if the pregnant person maintains an undetectable viral load while pregnant. Finally, research shows that effective treatment greatly reduces the risk of HIV transmission between people who share drug equipment.

If you have HIV, take HIV treatment and maintain an undetectable viral load…

when you have sex

you will not pass HIV to your sex partners


during pregnancy and delivery

you will not pass HIV to your fetus or baby


if you use injection drugs and share needles or other equipment

you greatly reduce the risk of transmission (we don’t know by how much)

In short, effective HIV treatment not only treats HIV but it can also prevent HIV. Hence the term treatment as prevention (TasP).

The World Health Organization has said, “It is certain that TasP needs to be considered as a key element of combination HIV prevention and as a major part of the solution to ending the HIV epidemic.” If you want to know more about this way of preventing HIV and how you can make it work for you, read on.

First, a few basics

What is an undetectable viral load?

HIV viral load refers to the amount of HIV in the blood of a person living with HIV. If you take HIV treatment consistently, you can reduce the viral load to a level too low to be detected by a blood test. Once your viral load has fallen below this level, it is said to be undetectable. For most people, this occurs after taking HIV treatment consistently for 3 to 6 months. Having an undetectable viral load is good for your immune system and for your long-term health.

Having an undetectable viral load does not mean you are cured of HIV. The virus is still in the body. If you stop taking HIV treatment or miss too many doses, your viral load will once again become detectable.

How do I know if I’m undetectable?

The only way to know is to have a blood test, called a viral load test, regularly. (You and your doctor will decide how often you should get tested, probably every 3 to 6 months.) If your viral load becomes detectable again, there may be a risk of HIV transmission.

Some people see occasional blips in their viral load. A blip is when your viral load becomes detectable at a very low level on one test and then becomes undetectable again on the next test. A single blip is not cause for alarm, but if you have two detectable results in a row, talk to your doctor.

How can I make treatment as prevention work for me?

You can make this prevention strategy work for you by taking your HIV medications as prescribed and by seeing your doctor regularly. Your ongoing healthcare should include viral load blood tests.

Wait until you’ve had at least 2 undetectable results in a row over a 6-month period before depending on this strategy.

To make this strategy keep working for you, adherence is key. This means taking your HIV meds every day, as prescribed.

I need some help taking my meds on time.

To help you stay on top of your pill-taking schedule, you can:

  • set an alarm on your cell phone or watch to remind you that it’s time to take your pills
  • use a dosette to organize your pills
  • ask your pharmacist to package your pills in blister packs
  • if you have a smartphone, download a free adherence app

If you’re having trouble taking your drugs as prescribed, talk to your doctor, nurse, pharmacist and/or local HIV organization.