HIV Prevention

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Pre-Exposure Prophylaxis (PrEP)

Last Reviewed: August 7, 2019

Key Points

  • Pre-exposure prophylaxis (PrEP) is when people who don’t have HIV but who are at high risk of getting HIV take HIV medicine every day to reduce their chances of HIV infection.
  • The HIV medicine used for PrEP is called Truvada. 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 high risk of getting HIV take HIV medicine every day to reduce their chances of HIV infection. The HIV medicine used for PrEP is called Truvada. If a person is exposed to HIV through sex or injection drug use, having the PrEP medicine in the bloodstream can often 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 high risk of becoming infected with 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 and in an ongoing sexual relationship with an HIV-positive partner. This recommendation also includes anyone who isn’t in a mutually monogamous relationship with a partner who recently tested HIV negative, and:

  • is a gay or bisexual man who has had anal sex without using a condom or been diagnosed with a sexually transmitted disease (STD) in the past 6 months, or
  • is a heterosexual man or woman who does not regularly use condoms during sex with partners of unknown HIV status who are at substantial risk of HIV infection (for example, people who inject drugs or women who have bisexual male partners).

PrEP is also recommended for people who have injected drugs in the past 6 months and have shared needles or works or been in a drug treatment program in the past 6 months.

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 even further.

Does PrEP cause side effects?

Some people taking PrEP may have side effects, like nausea, but these side effects are usually not serious and 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 you may be at high risk for HIV and that you might benefit from PrEP, talk to your health care provider. If you and your health care provider agree that PrEP may be a good choice for you, the next step is an HIV test to be sure you don’t already have HIV. If you are HIV negative and additional tests show that PrEP is likely safe for you, your health care provider can give you a prescription for PrEP. 

Many health insurance plans cover the cost of PrEP. Various medication assistance programs are available for people who may need help paying for PrEP.

What happens once I start PrEP?

Once you start PrEP, you will need to take PrEP every day. Studies have shown that PrEP is much less effective if 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. Read this fact sheet from CDC for information on how to use condoms correctly.   

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.

This fact sheet is based on information from the following sources:

From CDC: 

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