HIV Prevention

What is PrEP?

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

Three HIV medicines are approved by the U.S. Food and Drug Administration (FDA) for use as PrEP: 

• Truvada (or a generic equivalent), a pill taken by mouth every day.
• Descovy (or a generic equivalent), a pill taken by mouth every day.
• Apretude, a shot taken every 2 months.

Which medicine to use for PrEP depends on a person’s individual situation.

PrEP works by blocking the HIV life cycle, preventing the virus from taking hold and spreading if exposed during sex or injection drug use. However, its effectiveness relies on taking the medication as prescribed to ensure there is enough medicine in the bloodstream to stop the virus from spreading.

Should I consider taking PrEP?

PrEP is used by people who do not have HIV and are at high risk of being exposed to HIV through sex or injection drug use. If you have HIV, PrEP medicine is not for you.

Specifically, the Centers for Disease Control and Prevention recommends that you should consider PrEP if you are HIV negative, 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 infection (STI) in the past 6 months.

PrEP is also recommended if you inject drugs and you:

• 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 (nPEP) and:

• Report continued unsafe sex practices, 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?

Oral PrEP is most effective when taken consistently each day. CDC reports that consistent PrEP use reduces the risk of getting HIV from sex by about 99% and from injection drug use by at least 74%.

Currently, Apretude shots are recommended for people who are at risk of getting HIV from sex. Because its effectiveness has not been evaluated for receptive vaginal sex, Descovy is not recommended for women who are at risk of getting HIV.

Although getting HIV is unlikely when taking PrEP as prescribed, it can still occur. People who get HIV while taking PrEP may acquire HIV drug resistance. People who acquire HIV drug resistance from PrEP may have fewer HIV treatment options, though a health care provider can still help identify effective options.

Adding other prevention methods, such as condom use, along with PrEP, can further reduce your risk of getting HIV.

Does PrEP cause side effects?

In some people, PrEP can cause side effects, such as nausea, diarrhea, headache, dizziness, depression, and insomnia. These side effects are not serious and generally go away over time. However, in rare cases, more serious side effects such as kidney failure and lactic acidosis can occur.

Before taking PrEP, consult with your health care provider about any potential side effects. If you are taking PrEP, tell your health care provider immediately if you have any side effects that bother you or that do not go away.

What should you do if you think that PrEP can help you?

If you think PrEP may be right for you, see a health 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 have a negative HIV test immediately before starting PrEP.

How often should you take PrEP?

Oral PrEP: People taking oral PrEP (Truvada or Descovy) need to take their PrEP pills every day. This is the only CDC- and Food and Drug Administration (FDA)-recommended way to take oral PrEP for HIV prevention.

Some people may take PrEP “on demand” when they think they may acquire HIV. This method of taking PrEP for HIV prevention is not recommended by the CDC or FDA and should only be considered if it is recommended by your health care provider.

On-demand PrEP relies on a “2-1-1” schedule, in which you take two pills 2 to 24 hours before sex, one pill 24 hours after the first dose, and another pill 24 hours after the second dose.

Injectable PrEP: If you are taking Apretude, do not miss any injections (every two months). PrEP is much less effective when it is not taken as prescribed, which increases your risk of getting infected with HIV and acquiring HIV drug resistance.

What else should you know about PrEP?

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

If you inject drugs, avoid sharing needles or other drug injection equipment with other people. Although HIV PrEP reduces the risk of transmission from injection drug use, the risk of getting HIV remains much higher from injecting drugs than from sex.

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

If you do become HIV positive, you will need to take other medicines to treat HIV. PrEP medications and protocols are not approved for treatment of people with HIV.

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

From CDC: 

• Preventing HIV with PrEP
• PrEP Medication Guide: Reduce Your Risk of Getting HIV
• Now’s the Time to Find Out About PrEP and PEP

From DailyMed:

• Truvada
• Descovy
• Apretude

Also see the HIV Source collection of HIV links and resources.