PrEP, PEP, Condoms and U=U: HIV Prevention Options Compared

The options side by side

PrEP: prevention before exposure

PrEP is medicine taken by people without HIV to prevent getting it. CDC describes it as being for adults and adolescents who may be exposed through sex or injection drug use. There are four FDA-approved options:

• Daily pills: generic Truvada (F/TDF), Truvada, or Descovy (F/TAF). Descovy isn't indicated for receptive vaginal sex.
• Shots: Apretude every 2 months, or Yeztugo every 6 months.

How well it works: NIH says PrEP reduces the risk of HIV from sex by about 99% when taken exactly as prescribed, and PrEP pills reduce the risk from injecting drugs by as much as 74%. Daily pills take time to build up. CDC says about 7 days for receptive anal sex and about 21 days for receptive vaginal sex and injection drug use.

Trade-offs: it needs an HIV test before starting and regular testing after, and it doesn't prevent other STIs. Compare the forms in oral vs injectable PrEP, and see how to get it free on our free PrEP page.

PEP: the emergency option

PEP is a 28-day course of HIV medicines started after a possible exposure. CDC says it must start within 72 hours, and the sooner the better. It's meant for emergencies, not as a regular plan. If you find yourself needing PEP more than once, PrEP is usually the better fit, and you can move from PEP straight onto PrEP after a negative HIV test.

Emergency rooms, urgent care, some clinics and telehealth services can start PEP. See how to get PEP fast.

U=U: treatment as prevention

CDC states that people with HIV who take treatment and have an undetectable viral load will not transmit HIV through sex. This is called Undetectable = Untransmittable, or U=U. CDC also says most people can get the virus under control within six months of starting treatment, as long as they take it as prescribed.

In practice, U=U depends on:

• the partner with HIV taking treatment consistently,
• regular viral load tests confirming they're undetectable, and
• open communication if treatment is interrupted.

Many mixed-status couples rely on U=U. Some HIV-negative partners also use PrEP, for example while their partner is reaching undetectable, if testing is irregular, or if there are other partners. Our guide for couples goes deeper.

Condoms

Condoms, external or internal, are the one tool here that also helps prevent other STIs and pregnancy. CDC recommends them as a way to reduce the chance of getting or transmitting HIV through sex, and notes that PrEP doesn't protect against other STIs or pregnancy.

Their limitation is human. They have to be used correctly every time, and they can break or slip. That's where PrEP and PEP serve as backups. Using condoms some of the time while on PrEP is common and fine.

For injection exposure: sterile supplies

For people who inject drugs, hormones or anything else, new sterile needles, syringes and equipment for every injection prevents HIV and hepatitis C. CDC's guidance tells PrEP prescribers to offer PrEP to people who inject drugs and link them to syringe services. Oral PrEP is the option studied for injection exposure.

Combining tools: common combinations

What each option asks of you

Effectiveness numbers assume an option is used as intended, so the practical question is which one you can stick with.

• Daily PrEP pills ask for a daily habit, a clinic or telehealth check-in about every 3 months, and lab tests. They're easy to start and easy to stop.
• PrEP shots ask you to keep injection appointments, every 2 months for Apretude or every 6 months for Yeztugo, with an HIV test each time. In exchange, you don't have to remember daily pills. They linger in the body after you stop, so stopping takes a plan. See our injectable PrEP guide.
• PEP asks for speed, getting care within 72 hours, and then 28 days of daily medicine plus follow-up testing.
• U=U asks the partner with HIV to stay on treatment and get regular viral load tests, and both partners to talk openly if anything changes.
• Condoms ask for in-the-moment consistency and correct use every time. They need no prescription and no appointment.
• Sterile supplies ask for a reliable source, such as a syringe services program or pharmacy, so you never have to share.

Your answer can change over time. Plenty of people use condoms and PEP before starting PrEP, switch from pills to shots, or come off PrEP when a relationship settles into U=U. A plan that fits now is better than a perfect plan you can't keep.

Testing ties it all together

Whatever mix you choose, regular testing is the common thread. HIV testing is required for PrEP and confirms you're negative. STI testing catches the infections PrEP and U=U don't prevent. Viral load testing is what makes U=U reliable. Our sister site covers how often to test with new or multiple partners, and our free STI testing guide shows where to get it at no cost.

This guide is general health information, not medical advice, and it doesn't replace a conversation with a clinician who knows your history. Guidance and program rules change; we last reviewed this page on October 12, 2026. Spot something out of date? Tell us.