FAQ: Pre-Exposure Prophylaxis (PrEP) for HIV

Medically Reviewed by Jonathan E. Kaplan, MD on October 22, 2019

Because there's currently no cure for HIV, it's better to prevent an  infection if you can than to take medicine for the rest of your life.

For years, the most common prevention method has been condoms. Newer methods, like PrEP, are showing real promise, helping to lower the chance of infection for people who are HIV-negative. And both men and women can use it.

What is PrEP? How does it work?

PrEP stands for pre-exposure prophylaxis. It's a pill you can take when you don't have HIV but are likely to get the virus, perhaps because of sex or injection-drug use. It helps before you're infected, so HIV can't settle into your body and spread.

The PrEP medications sold as Descovy or Truvada, which are a combination of two drugs -- tenofovir and emtricitabine -- which taken correctly prevents HIV from taking hold in your body. There's no generic version of PrEP yet.

You need to take PrEP medicine once a day, every day.

How effective is it?

Skipping a dose or not taking PrEP regularly lowers the pill's ability to protect you. If you take it:

  • Every day, your level of protection is around 99%
  • 4 days a week, your level of protection is around 96%
  • 2 days a week, your level of protection is around 76%

It can take 7-20 days from when you take your first pill until it's most effective.

Descovy is the newer of the approved drugs and, unlike Truvada, it is not yet known if Descovy will protect HIV-negative women who have sex with an HIV positive man,

Is it safe?

The first PrEP medication, Truvada, was approved by the FDA in 2012 and Descovy was aproved in 2019. They may cause nausea, stomach upset, and dizziness, but these typically go away over time. None of the side effects have been life-threatening. Even after taking PrEP for 5 years, people aren't having health problems because of it.

And you can't get HIV from taking PrEP, because it's not a vaccine. There's no HIV in it.

PrEP doesn't seem to cause problems when you take it while you're using hormonal birth control, medication for depression, or alcohol and other party drugs.

If you have kidney or bone problems, though, let your doctor know before you start taking PrEP medication.

We're still learning how PrEP later affects kids whose mothers used it during pregnancy and breastfeeding.

Could PrEP work for me?

It doesn't matter what your gender identity and sexual orientation are. It's a good option for someone in any of these situations:

  • In an ongoing relationship with an HIV-positive partner
  • Has sex with multiple partners and doesn't always use condoms
  • Injects drugs or shares needles

If you're a woman who wants to have a baby with an HIV-positive man, ask your doctor about PrEP. It may be a way to lower the chances of you and your baby getting HIV.

Research is still being done on the effects of taking PrEP when you're transgender and having hormone therapy. No bad reactions have been reported so far.

Will PrEP work if I might already have HIV?

For PrEP to protect you, it needs to be taken before you come in contact with the virus. PrEP isn't a cure for HIV.

If you think you've been exposed, call your doctor right away or head to the emergency room. If you start taking a different kind of medication called PEP (post-exposure prophylaxis) within 72 hours, it can lower your odds of HIV infection.

If I'm taking PrEP, do I still need to use condoms?

PrEP can stop you from getting HIV, but it doesn't protect you from other sexually transmitted diseases like syphilis, chlamydia, and gonorrhea, so you'll still need condoms for that. PrEP also doesn't prevent pregnancy.

You should visit your doctor every 3 months for an HIV test and follow-up care while you're taking PrEP.

When can I stop taking it?

It isn't a pill you have to take forever. You get to decide when to start and stop PrEP. Just remember that if you don't take it regularly, you aren't as safe.

Once you've started taking PrEP, you should stay on it for at least a month after you were last exposed to HIV.

If you think that you're no longer at risk of getting HIV, talk with your doctor before you stop taking PrEP.

Where can I get PrEP?

You need a prescription for it, from any health provider -- doctor, nurse practitioner, or physician assistant -- who is qualified. You might need to contact your local health department or a local AIDS organization to find someone who understands what it is and is comfortable writing the prescription for you.

You'll also need to get an HIV test first to make sure you don't already have the virus.

How much does it cost?

PrEP is expensive -- it can cost as much as $13,000 a year without insurance. Most insurance plans do cover Truvada, which means you'd pay your normal copay amount for brand-name drugs.

Coverage differs from state to state, but PrEP should also be covered by Medicaid and Medicare.

If you have to pay for PrEP yourself, there are financial assistance programs that may help, including from the drug manufacturer, public health services, and clinical trials.

WebMD Medical Reference



CDC: "PrEP." "Pre-Exposure Prophylaxis." "What is PrEP?" "The Research," "The Questions About PrEP."

Harvard Health Publishing: "PrEP: Protection against HIV in a pill?"

Science Translational Medicine: "Emtricitabine-Tenofovir Concentrations and Pre-Exposure Prophylaxis Efficacy in Men Who Have Sex with Men." "The Questions About PrEP."

Human Rights Campaign: "Is PrEP Right For Me?"

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