Why the risk is higher

Being gay or bisexual doesn’t make anyone more vulnerable to HIV. Two other things do the work.

HIV is more common among partners. UNAIDS estimates that gay men and other men who have sex with men are about 23 times more likely to acquire HIV than the general population. So a male partner of unknown status is more likely to have HIV than a random member of the public.

Anal sex carries the most risk per act. CDC says being the bottom makes you more likely to get HIV than being the top. With a partner who has HIV and isn’t on treatment, one act is estimated at:

  • Bottoming (receptive anal sex): 1.4% (about 1 in 72)
  • Topping (insertive anal sex): 0.11% (about 1 in 910)
  • Oral sex: 0.01% (about 1 in 10,000)

With a partner of unknown status

A partner of unknown status may well not have HIV, so the estimate is much lower than the figures above. For one act without a condom:

  • Bottoming, United States: 0.05% (about 1 in 2,000)
  • Topping, United States: 0.004% (about 1 in 25,000)
  • Bottoming, United Kingdom: 0.01% (about 1 in 9,800)
  • Giving oral sex, United States: 0.00036% (about 1 in 280,000)

The calculator applies the higher likelihood automatically whenever both partners are men. If you’re bisexual, enter each partner separately: the figures for sex with women are different. See HIV risk from vaginal sex.

PrEP

PrEP (pre-exposure prophylaxis) is medicine taken by people without HIV to prevent it. Taken as prescribed, it lowers the risk from anal sex by about 99%. Bottoming on consistent PrEP with a partner who has HIV comes to 0.014% (about 1 in 7,200).

There are three main options: daily pills, event-driven pills taken around sex (an option for some men who have sex with men), and long-acting injections. A clinic can help you choose. See PrEP and PEP and HIV risk on PrEP.

Condoms, U=U and circumcision

  • Condoms lower risk by about 80% in real-world use. Bottoming with a condom and a partner who has HIV: 0.28% (about 1 in 360).
  • U=U. A partner with HIV who keeps an undetectable viral load on treatment doesn’t pass HIV on through sex. See U=U.
  • Circumcision lowers men’s risk in vaginal sex, but a Cochrane review found the evidence for men who have sex with men inconclusive.

How often to test

CDC recommends that everyone aged 13 to 64 test for HIV at least once, and that men who have sex with men test at least once a year. It adds that sexually active gay and bisexual men may benefit from testing every 3 to 6 months. You can find free testing in the United States at gettested.cdc.gov, and our HIV testing guide covers the options, including home tests.

Regular STI checks matter too. Other STIs make HIV easier to pass on, and the calculator multiplies the estimate by 2 if either partner has one.

What to do now

Sex without a condom or PrEP in the last 72 hours? If your partner has HIV and isn’t on effective treatment, or you don’t know their status, ask about PEP (post-exposure prophylaxis) now at an emergency department, urgent care center or sexual health clinic. It must start within 72 hours, ideally within 24. How to get PEP

  1. Recent exposure: go for PEP, taken daily for 28 days. Ask about moving onto PrEP when the course ends.
  2. No recent exposure: test now, and set a routine of every 3 to 6 months if you’re sexually active.
  3. Starting PrEP: you’ll need an HIV test first and regular tests while you’re on it.
  4. Talk with partners about status, testing and treatment. A partner who keeps an undetectable viral load can’t pass HIV on through sex.