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HIV Prevention

Pre-Exposure Prophylaxis (PrEP)

Last Reviewed: September 24, 2020

Key Points

  • Pre-exposure prophylaxis (PrEP) is when people who don’t have HIV but who are at risk of getting HIV take HIV medicine every day to prevent HIV infection. PrEP is used by people without HIV who are at risk of being exposed to HIV through sex or injection drug use.
  • Two HIV medicines are approved by the U.S. Food and Drug Administration (FDA) for use as PrEP: Truvada and Descovy. PrEP is most effective when taken consistently each day.
  • The Centers for Disease Control and Prevention (CDC) reports that studies have shown that consistent use of PrEP reduces the risk of getting HIV from sex by about 99% and from injection drug use by at least 74%.

What is PrEP?

PrEP stands for pre-exposure prophylaxis. The word “prophylaxis” means to prevent or control the spread of an infection or disease.

PrEP is when people who don’t have HIV but who are at risk of getting HIV take HIV medicine every day to prevent HIV infection. PrEP is used by people without HIV who are at risk of being exposed to HIV through sex or injection drug use. Two HIV medicines are approved by the U.S. Food and Drug Administration (FDA) for use as PrEP: Truvada and Descovy. Which medicine to use for PrEP depends on a person’s individual situation.

If a person is exposed to HIV through sex or injection drug use, having the PrEP medicine in the bloodstream can stop HIV from taking hold and spreading throughout the body. However, if PrEP is not taken every day, there may not be enough medicine in the bloodstream to block the virus.

Who should consider taking PrEP?

PrEP is for people who don’t have HIV but who are at risk of getting HIV through sex or injection drug use. 

Specifically, the Centers for Disease Control and Prevention (CDC) recommends that PrEP be considered for people who are HIV negative who have had anal or vaginal sex in the past 6 months and:

  • have a sexual partner with HIV (especially if the partner has an unknown or detectable viral load), or
  • have not consistently used a condom, or
  • have been diagnosed with a sexually transmitted disease (STD) in the past 6 months.

PrEP is also recommended for people without HIV who inject drugs and:

  • have an injection partner with HIV, or
  • share needles, syringes, or other equipment to inject drugs.

PrEP should also be considered for people without HIV who have been prescribed non-occupational post-exposure prophylaxis (PEP) and:

  • report continued risk behavior, or
  • have used multiple courses of PEP.

If you think PrEP may be right for you, talk to your health care provider.

How well does PrEP work?

PrEP is most effective when taken consistently each day. CDC reports that studies have shown that consistent use of PrEP reduces the risk of getting HIV from sex by about 99% and from injection drug use by at least 74%. Adding other prevention methods, such as condom use, along with PrEP can reduce a person’s risk of getting HIV even further.

Does PrEP cause side effects?

In some people, PrEP can cause side effects, such as nausea. These side effects aren’t serious and generally go away over time. If you are taking PrEP, tell your health care provider if you have any side effect that bothers you or that does not go away.

What should I do if I think PrEP could help me?

If you think PrEP may be right for you, see a heath care provider. PrEP can be prescribed only by a health care provider. If your health care provider agrees that PrEP may reduce your risk of getting HIV, the next step is an HIV test. You must be HIV negative to start PrEP.

What happens once I start PrEP?

Once you start PrEP, you will need to take PrEP every day. PrEP is much less effective when it is not taken every day.

Continue to use condoms while taking PrEP. Even though daily PrEP can greatly reduce your risk of HIV, it doesn’t protect against other STDs, such as gonorrhea and chlamydia. Combining condom use with PrEP will reduce your risk of HIV even further, as well as protect you from other STDs.  

You must also take an HIV test every 3 months while taking PrEP, so you’ll have regular follow-up visits with your health care provider. If you are having trouble taking PrEP every day or if you want to stop taking PrEP, talk to your health care provider.