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

Safer Sex

When you maintain an undetectable viral load, you cannot pass HIV to the people you have sex with. This is true for oral sex, vaginal sex and anal sex. It is true for sex with a condom and sex without a condom.

We can say with confidence that undetectable HIV is sexually untransmittable: u=u.

Studies show that a person will not transmit HIV sexually if their viral load is below 200 copies/ml; however, the ideal treatment outcome for a person’s long-term health is to maintain an undetectable viral load (usually 50 copies/ml or less).

How do we know this?

Large international studies have confirmed that when an HIV-positive person who has an undetectable viral load has sex with an HIV-negative person, they do not pass HIV. The evidence is clear.

What about STIs?

When you have an undetectable viral load, you can still give and get other STIs (sexually transmitted infections), such as chlamydia, herpes, gonorrhea and syphilis. However, condoms can reduce the risk of many STIs, so you might want to double up and use HIV treatment and condoms.

If I have an undetectable viral load, do I still need to tell someone I have sex with that I have HIV?

If you have an undetectable viral load, you are not putting your sex partner at risk for HIV, but Canadian law does require that you tell your sex partner that you have HIV in certain circumstances. For the most up-to-date information on when people living with HIV have a legal duty to disclose their HIV status, contact the HIV/AIDS Legal Network (

What if I have a detectable viral load?

Clearly, achieving an undetectable viral load has numerous benefits: In addition to significant health benefits, it is an effective way to prevent HIV transmission. If your viral load remains detectable, work with your medical team to find a combination of meds that might work better for you.

If you are adherent and you continue to have a detectable viral load, rest assured that there are other things you can do to stay healthy and prevent transmission. Other highly effective ways to prevent HIV include using condoms and (for HIV-negative people) PrEP. 

What is PrEP?

PrEP (pre-exposure prophylaxis) is an effective prevention strategy that involves an HIV-negative person who is at risk for HIV taking a certain kind of HIV medication. Once on PrEP, it is important to take the medication as prescribed and to see a doctor or nurse every three months to get tested for HIV and other STIs and to check for side effects.

What is PEP?

PEP (post-exposure prophylaxis) involves an HIV-negative person taking HIV medications immediately after being exposed to HIV to reduce their risk of HIV infection. PEP consists of a combination of two to three drugs that should be taken as soon as possible, within 72 hours of being exposed to HIV. These drugs need to be taken every day exactly as prescribed for four full weeks.