Post-Exposure Prophylaxis (PEP)

Medically Reviewed by Poonam Sachdev on April 28, 2022
Written by Matt Smith
3 min read

Post-exposure prophylaxis (PEP) is medicine you take after you’ve come into contact with HIV, the virus that causes AIDS, to lower your chance of infection.

You must start PEP within 72 hours (3 days) after you were exposed to HIV. The sooner you start it, the better. It has little to no effect if you start it 3 days or more after exposure.

PEP can lower your risk of HIV infection by 80% if you take it as your doctor prescribes.

PEP may help:

  • People who think they might have been exposed to HIV during sex
  • People who have been sexually assaulted
  • Drug users who recently shared needles or other related items
  • Health care workers who think they've been exposed to HIV on the job

If you think you were exposed to HIV, go to the hospital or see your doctor as soon as possible. They can help you figure out whether you need PEP.

The same drugs that treat HIV can fight the virus as it tries to infect you. These medications are called antiretrovirals.

PEP is a combination of three drugs. You take them once or twice a day for 28 days:

  • For adults, the CDC recommends tenofovir, emtricitabine (these two drugs come in one pill), and a third drug, either raltegravir or dolutegravir.
  • Women who are in early pregnancy, who are sexually active and could become pregnant while taking PEP, or who were sexually assaulted without birth control should take raltegravir rather than dolutegravir because of a risk of birth defects.
  • Children 2 or older who need PEP usually get the same drugs in different doses.

Your doctor will take a sample of your blood when you start PEP and may want to test for other sexually transmitted diseases. You’ll need HIV tests after you’re through with PEP to make sure you didn’t get the virus.

If you're on PEP, use condoms when you have sex to lower the chances that you'll come into contact with HIV again or, if you have the virus, that you'll spread it.

If PEP doesn’t work and you get HIV, it might be because the virus resists some of the medications.

Side effects of PEP include:

Rarely, the drugs can cause serious health issues, including liver problems.

PEP is only for emergencies. Don’t use it in place of safe sex or new sterile needles.

If you're exposed to HIV a lot -- for example, because you have multiple sex partners or use injected drugs -- talk with your doctor about pre-exposure prophylaxis (PrEP). That’s a medicine you take every day to keep HIV from taking hold in your body.

If your doctor gives you PEP after you were sexually assaulted, the federal Office for Victims of Crime might cover part or all of your related health care costs.

If you work in health care and had contact with HIV on the job, your health insurance or workers’ compensation will probably pay for PEP.

If your doctor gives you PEP for another reason and you don’t have insurance or can’t get coverage, you might be able to get the drugs for free from the companies that make them. The doctor’s office or hospital can apply for you.