Antiretroviral medications not only helps people living with HIV. It also plays a role in preventing transmission of the virus.

Pre-exposure prophylaxis (PrEP): PrEP is an HIV prevention tool in which an HIV-negative person takes antiretroviral medication to reduce the risk of contracting HIV. Currently, their are two FDA-approved medications for PrEP: 

  • Truvada (tenofovir disoproxil fumarate/emtricitabine)
  • Descovy* (tenofovir alafenamide/emtricitabine)

*Descovy has not yet been indicated in individuals at risk of HIV from receptive vaginal sex

When antiretroviral medication builds up in the human body, it can stop HIV from replicating and establishing an infection. PrEP was approved in 2012 by the U.S. Food and Drug Administration (FDA) with the requirement that it be used every day, even during periods of minimal or low-risk sexual activity. Studies are exploring intermittent dosing strategies (for example, using PrEP only during high-risk periods). Researchers are also looking into injectable, long-lasting forms of PrEP as well as different medications that could be used as PrEP.

The Centers for Disease Control and Prevention (CDC) recommends PrEP for those who are HIV negative and at high risk including:

  • Sexually active gay and bisexual men without HIV
  • Sexually active heterosexual men and women without HIV
  • Sexually active transgender persons without HIV
  • Persons without HIV who inject drugs
  • Persons who have been prescribed non-occupational post-exposure prophylaxis (PEP) and report continued risk behavior, or who have used multiple courses of PEP

According to CDC recommendations, before prescribing PrEP, health care providers should thoroughly assess a patient’s HIV risk behaviors and also administer an HIV test. (More sensitive HIV tests can detect a more recent, or acute, infection; however, most home tests will not detect HIV during this “window period.”) Tests for STIs are recommended. So, too, are tests for kidney function—tenofovir is associated with kidney toxicity—and hepatitis B virus (HBV), given that Truvada is also active against HBV and must be used cautiously.

It is recommended that providers prescribe no more than a 90-day supply of PrEP and to offer extensive HIV risk-reduction counseling, adherence counseling and condoms. It is recommended that, before renewing Truvada scripts, providers follow up with patients every two to three months to test again for HIV, to assess adherence and HIV risk behavior, and to provide ongoing support and counseling. Kidney function testing is again recommended three months after a person first starts PrEP and yearly thereafter. Tests for common STIs are also recommended every six months, even if a person has no symptoms.

PrEP is appropriate for periods of time when people have greater risk for contracting HIV. Those periods may be short, long or recurrent, depending on the individual. The CDC also recommends that before people discontinue PrEP—whether because of safety concerns, a positive HIV test result, or a person requests to stop treatment—their providers should link them to HIV care (if a person has become infected) or ongoing HIV risk-reduction counseling and support. For people who have hep B, their providers should also discuss whether to continue treatment as a means to control their hepatitis.

How does PrEP work?
PrEP only works if you take it. Data from the iPrEx trial show that daily adherence reduces HIV risk between 96 percent and greater than 99 percent. Those who took four doses a week remained fully protected, and those who took two lowered their chance of getting HIV by 76 percent.

What about side effects?
Rates of side effects while on PrEP are low. Mild symptoms such as stomach cramps, headaches and loss of appetite may appear the first few weeks. Long-term use raises issues of kidney health and bone density. Health care providers should regularly test for kidney function.

What about drug resistance?
If you are HIV positive and start PrEP, the virus can become resistant to one or both meds in Truvada. This mutated virus is weaker and less likely to transmit. Still, it is important you are not in the window period of HIV infection when beginning PrEP.

Do I still need to use condoms?
PrEP is supposed to be used along with safer-sex practices, such as condom use and regular HIV testing.

How can I access PrEP?
At over $1,500 a month, PrEP is not cheap. Most insurance plans cover it, but you may have to work with your health care team before you get a prescription and coverage.

The Gilead Advancing Access program is available for qualified individuals in the United States who cannot afford Truvada or Descovy for PrEP. The program includes a co-pay assistance program for commercially insured individuals and a medication assistance program (MAP), which provides free medication for those who qualify based on financial need.

For more info, visit

Last Reviewed: August 23, 2020