PEP stands for post exposure prophylaxis. PEP is a series of pills you can start taking very soon after you’ve been exposed to HIV that lowers your chances of getting it. But you have to start PEP within 72 hours, or 3 days, after you were exposed to HIV, or it won’t work. The sooner you start, the better it works — every hour matters.

You take PEP 1-2 times a day for at least 28 days. The medicines used in PEP are called antiretroviral medications (ART). These medicines work by stopping HIV from spreading through your body.

Who can use PEP?

PEP is for people who may have been exposed to HIV in the last 3 days. PEP might be right for you if:

• You had sex with someone who may have HIV and didn’t use a condom, or the condom broke

• You were sexually assaulted

• You shared needles or works (like cotton, cookers, or water) with someone who may have HIV

If you were exposed to HIV in the last 3 days and want PEP, see a nurse or doctor or go to the emergency room immediately. Timing is really important. You must start PEP as soon as you can after being exposed to HIV for it to work.

PEP is for emergencies. It can’t take the place of proven, ongoing ways to prevent HIV — like using condoms, taking PrEP (a daily pill that lowers your chances of getting HIV), and not sharing needles or works. If you know you may be exposed to HIV often (like if you have a sexual partner or partners who may be HIV-positive), talk to your nurse or doctor about PrEP.

If you’re a health care worker and think you may have been exposed to HIV at work, go to your doctor or the emergency room right away. Then report the incident to your supervisor. HIV transmission in health care settings is extremely rare, and there are procedures and safety devices that can lower your chances of coming into contact with HIV while caring for patients.

How do I get PEP?

You can get PEP from emergency rooms, a Planned Parenthood Keystone health center, and some doctors’ offices, but call first to make sure they have PEP in stock. 

You can start PEP up to 72 hours (3 days) after you were exposed to HIV, but don’t wait — it’s really important to start PEP as soon as possible. So if you can’t get to a doctor or nurse right away, go to the emergency room as soon as you can. Every hour counts.

Before you get PEP, the nurse or doctor will talk with you about what happened, to decide whether PEP is right for you. They’ll give you a blood test for HIV (if you already have HIV, you won’t be able to use PEP). You’ll also be tested for Hepatitis B. And if you were exposed to HIV through sex, you’ll get tests for other STIs like gonorrhea, chlamydia, and syphilis.

What happens when I’m on PEP?

PEP isn’t just a one-time pill — it’s a regimen where you take many pills over many weeks. If your nurse or doctor gives you PEP, you’ll need to take medicine 1-2 times a day for at least 28 days (4 weeks). It’s important that you take every pill as directed and don’t skip doses, otherwise PEP may not work as well.

PEP isn’t 100% effective, and it won't prevent future HIV infections like PrEP can. So it’s important to keep protecting yourself and others from HIV while you’re on PEP. Use condoms every time you have sex. If you inject drugs, don’t share needles or works. This helps protect you from being exposed to HIV again. And it lowers the chances of giving HIV to others if you do have it.

If you develop symptoms like a fever or rash while using PEP, talk with your doctor. These may be signs of the beginning stages of HIV.

What are the side effects of PEP?

There can be side effects of PEP, like stomach aches and being tired. But PEP side effects aren’t dangerous, and they can be treated. Talk with your nurse or doctor if you have side effects that are really bothering you.

If PEP doesn’t work, you may have symptoms of the first stage of an HIV infection, like a fever or rash. If you have these symptoms while you’re on PEP, or within a month after finishing PEP, call your nurse or doctor.

What happens after I take PEP?

You need to visit your nurse or doctor for follow-up testing after you finish PEP. You’ll get another HIV test 4-6 weeks after you were first exposed to HIV, and then you’ll be tested again 3 months later. Depending on your situation, your doctor may recommend another HIV test 6 months later.

It’s really important to get these follow-up tests to make sure PEP worked. In the meantime, keep protecting yourself and others from HIV by using condoms when you have sex, and not sharing needles or works.