HIV medications have been tremendously successful in keeping HIV-positive people healthy. They’re also great at stopping HIV infections. Here’s more information about both.

What is PrEP?

PrEP stands for pre-exposure prophylaxis. PrEP is an effective way to prevent HIV infection. Currently, there is one method of PrEP approved by the FDA – taking one Truvada pill every day. Studies (iPrEx study and iPrEx OLE study) show that PrEP can reduce the risk of getting infected with HIV by 92-99% when taken daily.

PrEP 2-1-1 (or “intermittent”)  also has been shown to be effective; see below for more information.

Who is PrEP for?

PrEP is for HIV-negative people who may be at risk of HIV infection through sex or injection drug use. According to the CDC, PrEP should be considered for anyone who is HIV-negative and:

  • in an ongoing sexual relationship with an HIV-positive partner,
  • is not in a mutually monogamous relationship with a partner who recently tested HIV-negative,
  • is a gay or bisexual man who has had anal sex without using a condom or been diagnosed with an 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).

Consider talking to your healthcare provider to decide if PrEP is right for you.

How effective is PrEP?

The simplest answer: the more you take, the better it works. PrEP works very well to protect against HIV if it’s taken every day. You should commit to taking it every day, and seeing your healthcare provider every three months for an evaluation and lab testing that includes comprehensive STD screening ( Studies show that it offers a 92-99% reduction in HIV risk when taken regularly. When PrEP is taken less consistently, it doesn’t work as well to prevent HIV. PrEP does not protect people from any sexually transmitted infections (like gonorrhea, chlamydia, and syphilis, to name a few). Health organizations recommend that people who take PrEP combine it with other safe sex strategies – like using condoms, and Treatment as Prevention for HIV-positive partners – to reduce risk even more.

Also, it’s important to note that PrEP doesn’t begin working immediately. When you start taking PrEP, it takes at least seven days for the drug to become effective at preventing HIV. Also, if you intend to stop taking PrEP, you should keep on taking it for at least four weeks after your last potential exposure.

There have been, as of May, 2017, only three well-documented instances of people being infected with HIV while being on, and adherent, to PrEP. Two of the cases involved exposure to a strain of HIV that is resistant to many HIV drugs, so PrEP could not protect them against it. The third case was in a man who had condomless anal sex with approximately 150 different men in six months. This is out of an estimated 100,000 people who are taking PrEP in the U.S. This doesn’t mean that PrEP isn’t effective. It simply means that PrEP is not 100% effective (as are most things in healthcare and life).

Once daily Truvada is the most widely studied and only FDA approved version of PrEP. Other trials ( are currently underway to examine other forms of PrEP (including injectables, implants, and topical gels). However, until more data are available, anything other than Truvada should not be used for PrEP.

Side effects of PrEP

There are relatively few side-effects reported by people taking PrEP. Some people report experiencing “start-up syndrome” when they begin PrEP. This can include nausea, headache, and loss of appetite. Usually, symptoms are mild and stop after the first month.

Truvada-based PrEP is also associated with small decreases in bone mineral density (bone strength) in some people. People with greater bone density are less likely to suffer from broken bones or fractures after injury, which is why decreases in bone density can be worrying. Studies show that decreases in bone strength are usually small, not associated with fractures or broken bones, and that bone density recovers after people stop PrEP.

Truvada-based PrEP may also cause kidney abnormalities. Following-up with your healthcare provider every three months is important so that they can perform lab testing to ensure your kidneys are working properly and to determine if PrEP should be held or stopped for your safety.

Where to get PrEP

People at risk for HIV can get PrEP in a number of different ways. If you are currently in medical care and have medical insurance, you can talk to your regular healthcare provider about PrEP. Check out the CDC guide about how to talk about PrEP with your doctor here.

You can also look for PrEP-friendly medical providers through the national PrEP directory here. This website has a location-based tool so you can search by region. It includes providers who require insurance as well as those who don’t.

LGBT health centers or local AIDS service organizations in your area may also have PrEP services or have recommendations on how to access PrEP. Reach out to your local LGBT or AIDS service agencies for more information.

How to afford PrEP

If you have health insurance, you can expect to pay the normal co-pay for a brand-name drug for Truvada-based PrEP. This cost varies from plan to plan.

Without insurance, PrEP is not cheap. It can cost thousands of dollars every year. But there are ways to get Truvada for PrEP at no or low cost. A number of states have established their own PrEP Assistance Programs ( Most cover out-of-pocket expenses for the medication for insured patients and almost all programs cover the cost of clinical visits and lab tests regardless of health insurance coverage. In addition, Gilead Sciences (the manufacturer of Truvada) has a prescription assistance program.

Another option is to participate in a clinical research study or demonstration project of PrEP. You can search for PrEP studies that are now enrolling across the U.S. on the AVAC website.

What is PrEP 2-1-1?

PrEP 2-1-1 is named for a particular PrEP dosing schedule:

  1. 2 pills are taken 2 to 24 hours before sex
  2. 1 pill 24 hours after the initial dose
  3. 1 final pill 24 hours later.

PrEP 2-1-1 is also known as “on-demand,” “event-driven,” “sex-driven” and “intermittent” PrEP.

How effective is PrEP 2-1-1?

An ongoing French study of more than 1,500 gay/bi men has seen no new HIV infections among high-risk participants who opted either for PrEP 2-1-1 or daily PrEP to prevent HIV infection.

Previous studies have also demonstrated effective results. The most well-known study, named IPERGAY, showed that PrEP 2-1-1 reduced risk of HIV infection by 86% compared to placebo. The continuation of the study provided a real-world look at how people use PrEP 2-1-1. This part of the study found that PrEP 2-1-1 reduced risk of HIV infection by 97%.  Among those people having sex less frequently, there were zero HIV infections.

Overall, PrEP 2-1-1, when used correctly, seems to be an effective way to prevent HIV infection. It is important to note, however, that PrEP 2-1-1 is neither endorsed by the CDC, nor approved by the FDA, and is considered “off-label” use.

Who might benefit from PrEP 2-1-1?

While daily PrEP is currently the recommended way to take PrEP, PrEP 2-1-1 provides an alternative dosing strategy for gay men who would benefit from PrEP but find it hard to take a pill every day. It may be an option if you are able to anticipate when you’ll next have sex, and can take your pre-sex dose of PrEP 2 hours (preferably 24 hours) before then, and daily doses of PrEP for 48 hours after your last sexual encounter.

Who should not take PrEP 2-1-1?

PrEP 2-1-1 is only recommended for people having anal sex, since the drug may not be present at levels high enough if using PrEP 2-1-1 to protect vaginal tissues.  PrEP 2-1-1 has not been adequately studied in cis-women, men who have sex with women, transgender men and women, or people who inject drugs. Furthermore, PrEP 2-1-1 is not recommended for people with chronic Hepatitis B infection.

In addition, if you are not able to anticipate when you have sex and cannot take your pre-sex dose of PrEP at least 2 hours (and preferably closer to 24 hours) before sexual activity, 2-1-1 PrEP may not be right for you.  People who find it more difficult to plan ahead and take their pre-sex dose at least two hours ahead, or to remember to take a second and third dose afterwards, may instead benefit from daily use.

Whatever your decision is about PrEP, or PrEP 2-1-1, be sure to ask your healthcare provider. If you switch between 2-1-1 and daily PrEP use, you should retest for HIV prior to restarting if you’ve had a period of activity not covered by daily or 2-1-1 PrEP.


Want to learn more about PrEP? Check out these short videos and other resources. You’ll get a quick overview of what PrEP is, how well it works, and how to figure out if it may be right for you.

  • Are You Ready for PrEP? Video by the CDC
    Get quick and easy-to-understand info about PrEP to help you decide if PrEP might be the right option for you.
  • Is PrEP For You? Harlem United
    Q&A about PrEP and “PrEP conversations” videos.
  • Acute HIV and PrEP Fact Sheet: From the CDC
    It’s really important that people living with HIV do not to take PrEP. If you’ve recently started taking PrEP, and are worried that you’ve recently contracted HIV (either right before, or right after you started PrEP), find out what to do.

PEP stands for Post-Exposure Prophylaxis. PEP prevents HIV infection in people who have been recently exposed to HIV. If you are HIV-negative but recently had condomless sex with a guy whose HIV status you didn’t know, for example, consider taking PEP to prevent a possible HIV infection. If you have HIV, and think there’s a chance you exposed someone else to HIV, you can tell that person about PEP.

PEP is a four-week course of anti-HIV medications that prevent HIV infection. In order for PEP to work, it has to be started as soon as possible after the HIV exposure event.

That means if you think you’ve been exposed to HIV, and want to start taking PEP, do so as soon as possible. PEP has to be started within 72 hours (3 days) in order to work.

Should I go on PEP?

If you’re HIV-negative and your answer to any of the questions below is yes, talk to your doctor right away.

  • Did you bottom without a condom with someone who is either HIV-positive and not undetectable or someone whose HIV status you don’t know?
  • Did the condom break and you got a load up your butt?
  • Did you top someone raw who is either HIV-positive and not undetectable or someone whose HIV status you don’t know?
  • Have you shared needles with someone?

What is PEP for?

PEP is for HIV-negative people who may have been exposed to HIV during a single event. PEP is not a substitute for other proven HIV prevention methods, such as correct and consistent condom use, PrEP (pre-exposure prophylaxis), or use of sterile injection equipment.

How does PEP work?

You have to start PEP within 72 hours of exposure for PEP to work. Seek PEP right away if you think you’ve been exposed to HIV. Your doctor will determine what treatment is right for you based on how you may have been exposed to HIV.

PEP consists of 2-3 antiretroviral medications that are taken for 28 days. PEP is safe but may cause side effects like nausea in some people. These side effects can be treated and are not life threatening. PEP is not 100% effective; it does not guarantee that someone exposed to HIV will not become infected with HIV.

What happens after I start PEP?

Make sure you take your meds. PEP does not work if you do not take the medications.
Continue to use condoms with sex partners while taking PEP and do not use injection equipment that has been used by others. This will help avoid spreading the virus to others if you become infected.

Return to your healthcare provider for more HIV testing one month, three months, and six months after the potential exposure to HIV. Your healthcare provider will give you a follow-up schedule.

Adapted from Strut