Worried about a possible exposure? Get a clear-eyed number.

Topics

Answers to specific questions

• Condom broke? Your HIV risk and what to do

  If a condom broke, slipped or came off, treat that act as sex without a condom. The risk from one act is usually low, but if your partner has HIV or you don't know their status, PEP started within 72 hours can stop an infection.

• Can you get HIV from one time?

  Yes, it's possible to get HIV from one exposure, but it's unlikely. Even when a partner has HIV and isn't on treatment, most single acts don't pass it on, and with a partner whose status you don't know the chance is much smaller still.

• HIV risk from oral sex

  The chance of getting HIV from oral sex is very low. CDC says there is little to no risk, though ejaculation in the mouth with mouth ulcers, bleeding gums or genital sores can raise it.

• HIV risk from anal sex

  Receptive anal sex, or bottoming, carries the highest HIV risk of any type of sex. Insertive anal sex, or topping, carries much less. Condoms, PrEP and a partner's undetectable viral load each bring the risk down sharply, in the last case to zero.

• HIV risk from vaginal sex

  The HIV risk from one act of vaginal sex is low, even with a partner who has HIV and isn't on treatment, and much lower with a partner whose status you don't know. Women, as the receptive partner, face a higher risk per act than men.

• HIV risk after sex with a sex worker

  The HIV risk from one act with a sex worker is usually low, and very low if a condom was used and stayed on. It's higher than with other partners mainly because HIV is more common among sex workers in many countries. If there was no condom or it failed, consider PEP within 72 hours.

• HIV risk for gay and bisexual men

  Gay, bisexual and other men who have sex with men face a higher HIV risk than most groups, because HIV is more common among their partners and receptive anal sex carries the highest per-act risk. PrEP, condoms and partners on effective treatment bring that risk right down, and regular testing catches any infection early.

• HIV risk across many exposures

  HIV risk adds up with each exposure, but not by simple multiplication. With one regular partner, everything hinges on whether that person has HIV; with different partners, each new partner is a fresh chance, so the risk keeps climbing.

• How accurate is an HIV test at each week after exposure?

  A negative HIV test means more the longer you wait after the exposure. No test can detect HIV in the first week. A NAT (nucleic acid test) is conclusive from day 33, a lab antigen/antibody test from day 45, and rapid and home tests from day 90.

• What is the HIV window period?

  The window period is the time between getting HIV and when a test can detect it. It depends on the test: 10 to 33 days for a NAT, 18 to 45 days for a lab antigen/antibody test, 18 to 90 days for a rapid antigen/antibody test (finger-prick), and 23 to 90 days for antibody tests, including most home tests.

• Early HIV symptoms: a timeline, and why they can't tell you if you have HIV

  Some people get a short flu-like illness 2 to 4 weeks after getting HIV, but many have no symptoms at all, and the same symptoms have many other causes. Symptoms can't tell you whether you have HIV. Only a test can.

• Home HIV tests: how self-tests work and how accurate they are

  Most home HIV tests are antibody tests that use an oral swab or a drop of blood from your finger, with results in about 20 minutes. A negative result is only conclusive from 90 days after the exposure, and a positive result always needs a follow-up test at a clinic.

• Positive or reactive HIV test: what happens next

  A reactive or positive result on a rapid or home test isn't a final diagnosis until a follow-up lab test confirms it. If HIV is confirmed, starting treatment as soon as possible lets you live a long, healthy life. While your viral load stays undetectable, you won't pass HIV on through sex.

• HIV anxiety: coping with worry after a possible exposure

  Worry after a possible HIV exposure is common, and for most exposures the actual chance of HIV is low. The way through is a plan: check your real risk, ask about PEP if it's been less than 72 hours, and take a test once its window period has closed.

• HIV and other STIs: how they raise risk and why to test for both

  Having another sexually transmitted infection, such as syphilis, herpes, gonorrhea or chlamydia, can make HIV easier to get and to pass on. The calculator roughly doubles the risk when either partner has an STI, so test for both, and get any STI treated.

• U=U: undetectable means untransmittable

  A person with HIV who takes treatment and keeps an undetectable viral load (under 200 copies per milliliter of blood) does not pass HIV to sexual partners. This is what U=U means: undetectable equals untransmittable.

• How to get PEP within 72 hours

  Go to an emergency room, urgent care center, sexual health clinic or your own doctor as soon as you can and say you need PEP for a possible HIV exposure. PEP has to start within 72 hours, and the sooner you start, the better it works.

• More than 72 hours since a possible HIV exposure?

  After 72 hours, PEP is no longer recommended, because there isn't enough evidence that it still works. What helps now is testing at the right times, knowing which symptoms to act on, and planning protection for the future.

• HIV risk on PrEP: how protected are you?

  If you take PrEP as prescribed, your chance of getting HIV from sex is very low. Protection drops when doses are missed, takes time to build when you start, and doesn't extend to other STIs.

• Circumcision and HIV: how much does it protect?

  Circumcision partly protects men from getting HIV through vaginal sex, but it is not full protection. It doesn't protect the partners of men who already have HIV, and for sex between men the evidence is inconclusive.

• HIV exposure while pregnant or after giving birth

  During pregnancy and in the months after giving birth, HIV passes more easily through vaginal sex, so a possible exposure is worth acting on quickly. Pregnancy and breastfeeding are not reasons to avoid PEP, which must start within 72 hours.

• After sexual assault: HIV, PEP and getting care

  If you were sexually assaulted in the last 72 hours, try to get medical care as soon as you can. PEP can lower the chance of HIV, and the same visit can include emergency contraception and care for other infections. What happened is not your fault.

• How HIV is not transmitted: everyday contact and common myths

  HIV doesn't spread through everyday contact. You can't get it from hugging, shaking hands, closed-mouth kissing, saliva, sweat, tears, sharing food or drinks, toilet seats or insect bites, because none of these lets the virus reach your bloodstream.

• Can you get HIV from kissing? Saliva, biting and spitting

  No, you can't get HIV from kissing. HIV isn't transmitted through saliva, so closed-mouth kissing carries no risk, and deep kissing has only been linked to HIV in very rare cases where both people had bleeding gums or open sores.

• Needlestick injury: HIV risk and what to do

  The HIV risk from one needlestick is small, even when the needle was used on someone with HIV, and most needles weren't. Wash the wound with soap and water, report it, and get medical advice the same day, because PEP must start within 72 hours.

• HIV risk from sharing needles and injection equipment

  Sharing a needle with someone who has HIV carries more risk than any kind of sex except receptive anal sex, because their blood goes straight into your bloodstream. Using sterile equipment every time prevents it, and PrEP and PEP add protection.

• Blood in your eyes, mouth or a cut: HIV risk and first aid

  Blood on unbroken skin carries no HIV risk. Blood splashed into your eyes, mouth or a fresh wound carries a very small risk, even from someone with HIV. Rinse it off, and if the person may have HIV and it was in the last 72 hours, get advice about PEP.

• How long does HIV survive outside the body?

  Not long. HIV doesn't survive for long outside the human body, for example on surfaces, and it can't reproduce outside a person. Touching a surface or dried blood won't give you HIV. The one real exception is blood left inside a used syringe, where HIV can stay alive for weeks.

• Can you get HIV from a tattoo or piercing? Razors and toothbrushes too

  There are no known cases of anyone getting HIV from a tattoo or body piercing. It is possible in theory, but only if the equipment or ink contains blood from someone with HIV. A studio that uses new, sterile needles and fresh ink for each client removes that risk.

• HIV prevalence by country: how common HIV is, and what it means for you

  In most countries HIV is uncommon among adults, and even in the countries where it is most common, most people don't have it. With a partner of unknown status, your risk from one act is the chance they have HIV times the per-act risk, so it is usually far lower than people fear.