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Understanding Pre-Exposure Prophylaxis (PrEP) for HIV

Pre-exposure prophylaxis (PrEP) is medicine you take to lower your risk of HIV infection. When you use PrEP consistently, it can greatly reduce your risk. The information below will tell you how it works, who should consider using it, and how to use it safely.

Who should consider PrEP?

PrEP is advised for people who:

  • Do not have HIV

  • May have a higher risk of HIV infection

This includes:

  • People who have a partner with HIV, especially if their HIV is not well-controlled

  • People who have sex without condoms, especially with multiple partners or people with unknown HIV status

  • People who had a sexually transmitted infection (STI) in the past 6 months

  • People who inject drugs and share needles or other drug tools

How well does PrEP work?

The medicines in PrEP help stop the HIV virus from making copies of itself and infecting your body. Research has shown that when you take PrEP consistently, it can greatly reduce your risk of getting infected with HIV. It can reduce your risk by up to 99% during sex. It can reduce your risk by more than 70% if you use injected drugs. But keep in mind that PrEP doesn't protect you from other sexually transmitted infections (STIs).

What are the medicines for PrEP?

If PrEP is advised for you, your provider will give you a prescription for 1 of these:

  • Truvada. This is a pill that has 2 medicines. They are called emtricitabine and tenofovir disoproxil fumarate. You take it daily. But some people may be advised to take it before and after sex.

  • Descovy. This is a pill that has 2 medicines. They are called emtricitabine and tenofovir alafenamide. You take it daily. It’s not approved for people assigned female at birth.

  • Apretude. This medicine contains cabotegravir. It is given by a shot (injection). The shot is done monthly for the first 2 months, and then every other month.

Before starting PrEP, you will need to have some blood tests. These are to check for infections and to see how well your kidneys are working.

Are there any side effects?

Most medicines have some side effects. Most side effects of PrEP are mild and go away after a few days. The common ones include:

  • Nausea

  • Diarrhea

  • Headaches

  • Tiredness

  • Reaction at injection site (for shots)

If you have any severe or long-lasting side effects, tell your healthcare provider.

Paying for PrEP

Most health insurance covers PrEP fully, with no copay. This includes clinic visits and follow-up tests. State Medicaid programs also cover it. If you don’t have health insurance or Medicaid, you can enroll for free PrEP medicine at readysetprep.hiv.gov. Many states have PrEP assistance programs. Pharmaceutical companies also have these programs. Ask your healthcare clinic for more information about PrEP assistance in your area.

When you are taking PrEP

While you are on PrEP, you will need to:

  • Take the medicine exactly as instructed. You will get instructions for when to take the medicine. Take it exactly as your provider says. This is to make sure you get the most protection.

  • Stick to a routine. To get the most out of PrEP medicine that comes in pills, take it every day. Or take it if instructed just before and for 2 days after sex. For PrEP shots, don’t miss your appointments. Skipping doses could make PrEP not work as well to protect you from HIV.

  • Combine it with other protection. PrEP is best used with other protective steps. It's best to use condoms as well. Get tested for STIs regularly. Use needles safely if you inject drugs.

  • Get regular tests. You will need to have HIV tests, kidney function tests, and STI screenings while using PrEP. Have these tests as often as instructed.

What is PEP?

Post-exposure prophylaxis (PEP) is medicine to help prevent HIV infection after possible contact. It’s for emergency use if you had unprotected sex or were stuck by a used needle. PEP is a combination of medicines taken every day for 28 days. It helps to reduce the chances of the HIV virus taking hold in your body.

You need to start PEP quickly after contact with HIV. It works best within 72 hours (3 days) after contact. It’s best to take it as soon as possible. PEP is not a guarantee. But it greatly lowers the risk of HIV infection if started within 72 hours of possible exposure to HIV. If you may have had contact with HIV, call your healthcare provider right away. Or you can go to your local health clinic or urgent care.

Talk to a healthcare provider

If you think you might be at higher risk of HIV, talk to a healthcare provider who knows about PrEP. They will assess your risk and see if PrEP is the right option to protect your health.

Online Medical Reviewer: Barry Zingman MD
Online Medical Reviewer: Rita Sather RN
Date Last Reviewed: 4/1/2024
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