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.

PEP should be used only in emergency situations. It is not meant for regular use by people who may be exposed to HIV frequently.

How Do You Know If You Need PEP?

PEP may be right for you if you are HIV-negative or don’t know your HIV status, and you think you may have been exposed to HIV in the last 72 hours:

  • During sex (for example, you had a condom break with a partner of unknown HIV status or a partner with HIV who is not virally suppressed)
  • You were sexually assualted
  • Through shared needles, syringes, or other equipment used to inject drugs, or
    Through sexual assault

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. It might also be available at some health clinics, some doctors’ offices, and pharmacists’ offices (Updated 2021 – SB 325), 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 STDs like gonorrhea, chlamydia, and syphilis.

Some medical providers don’t know about PEP, or they don’t want to prescribe it because they don’t have all the facts about PEP. Please refer them to the following pages:

  • Comprehensive guidelines for prescribing PEP have been published by the Centers for Disease Control and Prevention (CDC) in A Clinical Practice Guidelinepdf icon,[1] including a Clinical Providers’ Supplementpdf icon.[2]
    • The Clinical Providers’ Supplement contains additional tools for clinicians providing PEP, such as a patient/provider checklist, patient information sheets, provider information sheets, a risk incidence assessment, supplemental counseling information, billing codes, and practice quality measures.
    • PEP Consultation Service for Clinicians 1-888-448-4911 (9 a.m. – 2 a.m. ET) For more information on the services offered through the PEPline, visit the National Clinicians Consultation Centerexternal.
  • Southern Nevada Health District PrEPing for Change
    • Call one of SNHD PrEP Navigators at (702) 759-1381 and Press 1 to be linked to a PrEP Navigator, they can also give you guidances regarding PEP.

How Long Do You Need to Take PEP?

If you are prescribed PEP, you will need to take the HIV medicines every day for 28 days.

You will also need to return to your health care provider at certain times while taking PEP and after you finish taking it for HIV testing and other tests.

How Well Does PEP Work?

PEP is effective in preventing HIV infection when it’s taken correctly, but it’s not 100% effective. The sooner you start PEP after a possible HIV exposure, the better.

While taking PEP, it’s important to use other HIV prevention methods, such as using condoms the right way, every time you have sex and using only new, sterile needles and works when injecting drugs

Does PEP Cause Side Effects?

PEP is safe, but the HIV medicines used for PEP may cause side effects like nausea in some people. In almost all cases, these side effects can be treated and aren’t life-threatening.

If you are taking PEP, talk to your health care provider if you have any side effect that bothers you or that does not go away.

PEP medicines may also interact with other medicines that a person is taking (called a drug interaction). For this reason, it’s important to tell your health care provider about any other medicines that you take.

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 medical provider 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.

Can You Take PEP Every Time You Have a Potential Exposure to HIV?

No. PEP should be used only in emergency situations. It is not intended to replace regular use of other HIV prevention methods. If you feel that you might be exposed to HIV frequently, talk to your health care professional about PrEP (pre-exposure prophylaxis).

Can You Get Help Paying for PEP?


Depending on the reason you are prescribed PEP, you may qualify for free or low-cost PEP medicines.

Paying for PEP After a Sexual Assault

Paying for PEP After an Exposure at Work

  • Your workplace health insurance or workers’ compensation will usually pay for PEP.

Paying for PEP for Another Reason

Last Updated: 06/2021

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