"Undetectable" means that a test cannot detect the virus in the blood of a person living with HIV, although extremely small amounts of HIV are still present. Someone who is "undetectable" for 6 or more continuous months while on treatment does not transmit the virus through sex.
Undetectable also means the virus is being well controlled by HIV meds, which is also called "viral suppression". If a person with undetectable HIV stops their medications, the virus will return to a detectable level which then increases the risk of transmission.
Undetectable. U=U, short for "undetectable = untransmittable". Treatment as prevention, or "TasP". Basically, these terms all mean the same thing: If a person living with HIV stays undetectable for 6 months or more while on treatment, they cannot transmit HIV through sex.
Three international studies showed no HIV transmissions among mixed-HIV-status couples when the partner with HIV was undetectable for 6 months or longer. This included more than 75,000 acts of reported condomless sex among mixed-status heterosexual and gay male couples. (The studies were HPTN 052, PARTNER and Opposites Attract.) To date worldwide there are no verified reports of someone getting HIV from a partner who is undetectable.
Other ways to prevent HIV infection (for HIV-negative partners in mixed-status couples)
External condoms are worn over the penis and sex toys to help protect against HIV and sexually transmitted infections (STIs). They are easy to use and may be available for free at local clinics and community-based organizations, and are sold at many drugstores and online.
Internal condoms are worn inside the vagina/front hole or anus and are another way to help prevent HIV infection and STIs. Although not as commonly used as external condoms, they may be offered for free by local clinics and community-based organizations, and are sold in some drugstores and online.
PrEP (pre-exposure prophylaxis):
PrEP is a pill that can prevent HIV infection when taken as prescribed. PrEP can be used by all sexes, all genders.
Ask your doctor about PrEP. They may be able to provide PrEP services or refer you to someone who can. We can also help you find a local PrEP-friendly provider.
PEP (post-exposure prophylaxis):
PEP is a 28-day pill prescription that can be taken by people who are not on PrEP and who may have been exposed to HIV in the past 72 hours. When taken as prescribed, PEP can help prevent HIV infection.
Call your doctor if you think you need PEP, or go to your local ER or urgent care facility to get it.
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For more information on the U=U campaign and the science behind U=U, visit Prevention Access Campaign.
Visit our U=U for advocates page for more in-depth resources and information.