HIV PrEP (pre-exposure prophylaxis) is medication taken by people who don’t have HIV to prevent them from getting it. When taken as prescribed, PrEP reduces the risk of getting HIV from sex by about 99%. It comes in two forms: a daily pill or a long-acting injection given every few months.
How PrEP Works in Your Body
PrEP contains antiretroviral drugs that block HIV from copying itself inside your cells. After you take the medication, it travels to the tissues where HIV typically enters your body and builds up to protective levels. If you’re then exposed to HIV, the virus can’t establish a permanent foothold because the drug is already present in those tissues, stopping the virus from replicating before it can spread.
This is why consistency matters. The medication needs to be at sufficient levels in your body at the time of exposure. Missing doses means lower drug concentrations and less protection.
The Four FDA-Approved Options
There are currently four FDA-approved PrEP medications, split between daily pills and long-acting injections.
Daily Pills
The two oral options are both single tablets taken once a day. The first, sold as Truvada, has been available the longest and is now also available as a generic, making it the most affordable option for many people. The second, sold as Descovy, uses a newer formulation of one of the same active ingredients. Both are effective, but they differ in side effect profiles: Descovy is gentler on the kidneys and bones, while Truvada has more long-term safety data behind it. One important distinction is that Descovy has only been studied and approved for people at risk through receptive vaginal sex and insertive or receptive anal sex. It has not been studied for people at risk through receptive vaginal sex who were assigned female at birth, so Truvada remains the recommended oral option for that group.
Long-Acting Injections
For people who don’t want to take a daily pill, there are two injectable options. Cabotegravir (brand name Apretude) is given as a shot in the gluteal muscle. You get the first two injections one month apart, then one injection every two months after that. In clinical trials, it reduced the risk of HIV infection by roughly two-thirds compared to daily oral PrEP, largely because injections eliminate the challenge of remembering a daily pill.
The newest option is lenacapavir (brand name Sunlenca), a subcutaneous injection given just twice a year after an initial loading phase. The startup process involves taking oral tablets and getting injections on days one and two, then receiving injections every six months going forward. This is the least frequent dosing schedule of any PrEP option available.
Who Can Take PrEP
PrEP is for anyone who is HIV-negative and has a realistic chance of being exposed to HIV. That includes people who have a sexual partner with HIV, people who don’t consistently use condoms, people who have been diagnosed with a sexually transmitted infection in the past six months, and people who inject drugs and share equipment. You don’t need to check every box. If you feel your circumstances put you at risk, you’re a reasonable candidate for a conversation about PrEP with a provider.
Before starting, you’ll need an HIV test to confirm you’re negative. This is non-negotiable: taking PrEP when you already have HIV can lead to drug resistance, making the virus harder to treat. You’ll also be screened for other STIs like chlamydia, gonorrhea, and syphilis. If you’re starting one of the oral pills, your provider will check your kidney function and screen for hepatitis B, since the medications can affect both.
What Ongoing Monitoring Looks Like
PrEP isn’t a set-it-and-forget-it prescription. If you’re on a daily pill, you’ll return to your provider at least every three months for an HIV test and a prescription refill (refills are limited to 90 days at a time for this reason). STI screening happens at regular intervals too, typically every six months for most people and every three months for gay and bisexual men with risk factors for recurrent infections. Kidney function is monitored yearly for everyone on oral PrEP, and more frequently if you’re over 50 or had borderline kidney numbers at the start.
If you’re on the injectable form, the monitoring schedule aligns with your injection visits. You’ll get an HIV test at every visit, starting one month after your first injection and continuing every two months after that. STI screening follows a similar pattern to oral PrEP, every four to six months depending on your risk profile.
Side Effects
Most people tolerate PrEP well. The most common early side effects are mild: nausea, headache, and fatigue that typically resolve within a few weeks of starting. These “start-up” symptoms affect a minority of users and rarely lead people to stop the medication.
The more notable long-term concerns are kidney function and bone density, both associated primarily with the older oral formulation (Truvada). PrEP can cause small, reversible decreases in kidney function and bone mineral density. The risk is higher if you’re over 50 or already have kidney problems, which is why regular lab monitoring is built into the prescribing protocol. Both effects reverse after stopping the medication. Serious allergic reactions are possible but rare.
For the injectable options, injection-site reactions like pain, swelling, or hardness at the injection spot are the most common complaint. These tend to be mild and improve with subsequent injections.
Cost and How to Access PrEP
The sticker price of PrEP can look daunting, but most people pay far less than the list price, and many pay nothing at all. Generic versions of Truvada have significantly lowered costs for the oldest oral option. Most private insurance plans cover PrEP with no cost-sharing, as it’s classified as a preventive service under the Affordable Care Act.
If you’re uninsured, every PrEP manufacturer runs a patient assistance program that provides the medication at no cost to people earning up to 500% of the federal poverty level. For Descovy or Truvada, you can call Gilead Sciences at 800-226-2056. For Apretude, contact ViiV Healthcare at 844-588-3288. If you have insurance but face high copays, co-payment assistance programs can cover thousands of dollars per year in out-of-pocket costs.
One limitation to be aware of: these manufacturer programs cover only the medication itself. The cost of clinic visits, lab work, and STI testing is separate. Many community health centers and sexual health clinics offer these services on a sliding-fee scale, and programs like the Ryan White HIV/AIDS Program or state-funded PrEP assistance programs can help fill the gap. Enrollment in assistance programs is typically valid for 12 months and requires annual renewal.
On-Demand PrEP
You may have heard of “2-1-1” or “on-demand” PrEP, a dosing strategy where you take two pills 2 to 24 hours before sex, one pill 24 hours later, and one more pill 24 hours after that. This approach was studied in a major trial and showed effectiveness for men who have sex with men, but it is not FDA-approved and is not recommended by the CDC. The only FDA-approved dosing schedules are daily oral pills or the injection timelines described above. If daily pills feel like too much and on-demand dosing appeals to you, the long-acting injectable options may be a better fit.