Emergency HIV prevention

Do I Need PEP After an HIV Exposure?

PEP is HIV medicine that can stop an infection before it starts, but only if you begin within 72 hours. Answer three quick questions, privately, to see whether you're still in the window and exactly what to do next.

If you may have been exposed in the last 72 hours, don't wait for this tool or an appointment, call or go to an emergency room, urgent care, or sexual health clinic now.

The basics

What is PEP?

PEP (post-exposure prophylaxis) is a 28-day course of HIV medicine taken after a possible exposure to stop the virus from taking hold. Taken correctly and started in time, it is highly effective, but it is an emergency measure with a hard deadline.

The window is 72 hours, and sooner is dramatically better: HIV can establish infection within about 24–36 hours, so PEP works best when started within hours, not days. If you have repeated exposures, the better long-term tool is PrEP, which is taken before exposure.

The clock

Why every hour matters

Within 24 hours

The ideal window. Start PEP as fast as you can, this is when it works best.

24–72 hours

Still worth it. PEP can be started up to 72 hours out; go get evaluated today.

After 72 hours

Too late for PEP. Switch to HIV testing now and PrEP for the future.

Getting PEP

Where to get PEP right now

Emergency room

Open 24/7 and among the most common places PEP is started. Say 'I need PEP for HIV.' They won't turn you away over cost.

Urgent care & clinics

Urgent care, sexual-health and HIV clinics, and many telehealth services can start PEP fast.

Pharmacies

In some states a pharmacist can start PEP directly. Call ahead and ask.

If cost worries you

Ask about assistance programs and manufacturer copay help, don't let cost delay starting.

Next steps

After PEP: protect yourself going forward

PrEP eligibility

Prevent HIV before exposure, see if PrEP is recommended for you.

HIV testing guide

When to test after an exposure and how to read the result.

Test-window calculator

When each test becomes reliable after a possible exposure.

Find testing & care

Clinics, at-home kits and free options near you.

Sources

Where this guidance comes from

The timing rules are from the CDC's 2025 PEP guidelines; the per-act figures are the CDC's own HIV transmission risk estimates. We don't reinterpret them.

Medically Reviewed & Fact-Checked · Updated July 2026

Reviewed by EasySTD Editorial Team

Compiled and checked by EasySTD's editorial team against CDC and public-health sources. This is educational information, not a substitute for advice from a licensed clinician. Our editorial guidelines →

3 Sources

Data & references

CDC: Nonoccupational PEP Guidelines (MMWR, 2025)https://www.cdc.gov/mmwr/volumes/74/rr/rr7401a1.htm
CDC: Clinical Guidance for PEPhttps://www.cdc.gov/hivnexus/hcp/pep/index.html
CDC: HIV Risk & Prevention Estimates (per-act risk)https://www.cdc.gov/hivpartners/php/riskandprevention/index.html

EasySTD is an information and comparison directory, not a healthcare provider. This tool is general information based on published CDC guidelines: it is not medical advice, a diagnosis, or a prescription, and it does not create a doctor-patient relationship. In an emergency, seek care immediately.

Good to Know

PEP: frequently asked questions

The 72-hour window, where to get it, and what counts as an exposure.

How long do I have to start PEP?

PEP must be started within 72 hours (3 days) of the exposure: and the sooner the better, ideally within 24 hours. HIV can establish infection within about 24–36 hours, so every hour counts. After 72 hours PEP is no longer effective and isn't recommended. If you think you were exposed and it's been less than 72 hours, don't wait for an appointment: go to an emergency room, urgent care, or sexual health clinic now.

Where do I get PEP?

Emergency rooms are among the most common places to start PEP, along with urgent care, sexual health and HIV clinics, and many pharmacies and telehealth services. Ask specifically for 'PEP for HIV.' It's a 28-day course of HIV medicine. If cost is a worry, say so: there are assistance programs, and an ER will not turn you away over the clock. Starting today matters more than where.

What actually counts as an HIV exposure?

The exposures that can transmit HIV are condomless anal or vaginal sex, sharing needles or injection equipment, and blood contact through a needlestick, when the other person has HIV that isn't virally suppressed. Oral sex is very low risk. Crucially, a partner who has HIV but is on treatment and reliably undetectable cannot transmit it (Undetectable = Untransmittable, U=U). If you're unsure whether they're undetectable, treat their status as unknown and get evaluated.

The risk number looks low, should I still get PEP?

Yes, if you're within the window and there was a real exposure, let a provider decide, not a percentage. The per-act figures are population averages that assume an untreated partner and no prevention; they can't tell you your personal outcome, and they go up with a high viral load or a co-occurring STI. PEP exists precisely because a preventable infection is worth preventing. Don't let a small-sounding number talk you out of care.

What if it's been more than 72 hours?

PEP won't help after 72 hours, but this isn't the end of the story. Get an HIV test now to establish a baseline, and test again at about 30 and 90 days (an early infection can take weeks to show up). Then talk to a provider about PrEP, daily or injectable medicine that prevents HIV going forward, so a future exposure is covered before it happens.

Is what I enter here private?

Completely. This tool runs entirely in your browser: your answers are never sent to a server, saved, or shared. Close the tab and they're gone. It's educational and can't diagnose you or prescribe PEP; only a clinician can do that.

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