Don’t wait to see if you feel ill, and don’t wait for a clinic appointment next week. PEP must start within 72 hours of the exposure, ideally within 24. If your usual clinic can’t see you today, go to an emergency department.

PEP (post-exposure prophylaxis) is a short course of HIV medicines taken after a possible exposure to stop the virus from taking hold. You take it every day for 28 days.

Where to go

The CDC advises talking right away to a health care provider, an emergency room doctor or an urgent care provider. In practice, your options are:

  • An emergency department. Usually the fastest option at night, on weekends and on holidays.
  • A sexual health clinic. Call first and ask whether they can see you today for PEP.
  • Urgent care or your own doctor, if they can see you today. Call ahead and ask whether they can prescribe PEP.

If the exposure happened during a sexual assault, there is extra care you can get at the same visit. See after sexual assault.

What to say

You don’t need to explain everything at the front desk. Something like this is enough: “I had a possible HIV exposure about 20 hours ago and I need PEP.”

The clinician will then ask some private questions. Being open helps them decide quickly:

  • When it happened, as close to the hour as you can.
  • What kind of contact it was, for example anal or vaginal sex without a condom, a broken condom, or a shared needle.
  • What you know about the other person: whether they have HIV, and if so whether they’re on treatment.
  • Whether you’re pregnant or breastfeeding, or take other medicines.

You’ll usually have a baseline HIV test so there’s a starting point to compare against. You may also be offered tests for other STIs.

You might leave with the full 28-day supply, or with a starter pack of a few days and a prescription for the rest. If you get a starter pack, fill the prescription straight away so you don’t run out.

Paying for PEP

Costs depend on where you live and your insurance, so ask at the visit. According to the CDC:

  • You may qualify for free or low-cost PEP medicines.
  • After a sexual assault, you may be able to get some or all of the cost of medicines and care reimbursed.
  • After an exposure at work, workplace insurance or workers’ compensation usually pays.
  • If you can’t get insurance coverage, your provider can apply for free PEP through manufacturers’ medication assistance programs.

Don’t let cost stop you from going. Ask about help with payment once you’re there.

Taking PEP and side effects

Take PEP exactly as prescribed every day for the full 28 days, at about the same time each day. The CDC says PEP is safe but may cause side effects like nausea in some people, and that in almost all cases these can be treated and aren’t life-threatening. If side effects bother you, call the clinic rather than stopping.

How much PEP helps depends on timing. The calculator assumes PEP started within 24 hours lowers the risk by about 90%, started within 48 hours by about 80%, and started within 72 hours by about 70%, as long as you take every dose.

Follow-up tests

You’ll need HIV tests after the course, even if you feel fine. The CDC recommends testing 4 to 6 weeks and 12 weeks after the exposure. Each time, it advises both a lab antigen/antibody test (blood from a vein) and a NAT (nucleic acid test, which looks for the virus itself). Negative results at 12 weeks rule out infection from this exposure. For more on timing, see HIV test accuracy by week.

If you get a fever, rash, sore throat or swollen glands in the weeks after the exposure, contact your clinic and ask for an HIV test.

Moving on to PrEP

PEP is for emergencies. The CDC says it isn’t the right choice for people who may be exposed to HIV often. If you expect more exposures, ask about PrEP (pre-exposure prophylaxis), which you take before exposure. CDC guidelines support moving straight from PEP to PrEP without a gap, with an HIV test at the end of the PEP course. Read more in HIV risk on PrEP.

What to do now

  1. Within 72 hours? Go now. Emergency department if nowhere else can see you today.
  2. Say you need PEP and when the exposure happened.
  3. Start the first dose as soon as it’s offered and take every dose for 28 days.
  4. Book your follow-up tests for 4 to 6 weeks and 12 weeks after the exposure.
  5. More than 72 hours? PEP is no longer recommended. Read what to do after 72 hours.