PEP (post-exposure prophylaxis) is a 28-day course of HIV medication you can get from an emergency room, urgent care clinic, or your regular doctor. The critical detail: it must be started within 72 hours of exposure, and the sooner you start, the better it works. If you think you’ve been exposed to HIV, go to the nearest emergency room now and ask for PEP by name.
Why the First 24 Hours Matter Most
PEP works by flooding your body with antiretroviral drugs before HIV has a chance to establish itself in your immune system. The clock starts at the moment of exposure, and every hour counts.
With a three-drug regimen (which is the current standard), PEP almost certainly prevents HIV infection if taken within 48 hours. Between 48 and 72 hours, effectiveness drops steeply regardless of how many drugs are used. And a two-drug combination is likely effective only if started within 24 hours. This is why the World Health Organization recommends starting PEP as soon as possible, ideally within the first 24 hours. After 72 hours, PEP is generally not offered because the window has closed.
Who Qualifies for PEP
PEP is appropriate after any suspected or known exposure to HIV. The most common scenarios include:
- Sex where a condom broke or wasn’t used with a partner who has HIV or whose status you don’t know
- Sharing needles, syringes, or other injection equipment
- Sexual assault
PEP also exists for healthcare workers and first responders who experience occupational exposures like needlestick injuries. The medications are the same, but occupational PEP (oPEP) is handled through separate workplace protocols. If you’re a healthcare worker, your employer should have a process for this.
PEP is not for people who are regularly exposed to HIV. If you’re frequently in situations where exposure is possible, PrEP (pre-exposure prophylaxis) is the daily medication designed for ongoing prevention.
Where to Go
Emergency rooms are the most reliable option, especially after hours or on weekends, because they’re open 24/7 and stock the medications. Urgent care clinics can also prescribe PEP, though not all locations carry the drugs on-site. Your primary care doctor or an infectious disease specialist can prescribe PEP during office hours, but given the time pressure, an ER visit is often the fastest route.
If you’re unsure where to go, you can call 1-888-788-PrEP to speak with someone who can help you find a nearby provider. Sexual health clinics and community health centers in many cities also offer PEP, sometimes with walk-in availability.
What Happens at the Visit
When you arrive, tell the provider you may have been exposed to HIV and need PEP. They’ll ask about the type of exposure, when it happened, and anything you know about the other person’s HIV status. The goal is to get the first dose into your system as quickly as possible, so most providers will start treatment before all lab results are back.
You’ll have blood drawn for an HIV test (to confirm you’re not already positive), along with baseline lab work. These results help guide the rest of your care but shouldn’t delay your first dose. You’ll leave with a prescription for a full 28-day supply.
The 28-Day Treatment
The standard PEP regimen is three antiretroviral drugs taken every day for 28 days. You’ll typically take a combination pill once a day plus a second medication either once or twice daily, depending on which drugs your provider prescribes. Completing the entire course is essential. Stopping early reduces effectiveness.
The most common side effects are nausea, diarrhea, tiredness, and headaches. These are generally mild and tend to improve as your body adjusts to the medication. If side effects are making it hard to keep taking the pills, talk to your provider. They may be able to switch you to a different combination or suggest ways to manage symptoms. Nausea, for example, often improves if you take the medication with food.
Follow-Up Testing
Taking PEP doesn’t replace the need for HIV testing afterward. You’ll need to be tested at specific intervals to confirm the treatment worked:
- Baseline: At your first visit, before or alongside starting PEP
- Week 4: Around the time you finish the 28-day course
- Week 12: The final test to confirm your HIV status
The week-12 test is the one that gives you a definitive answer. Until that result comes back negative, it’s important to use condoms and take precautions to avoid potentially passing HIV to others.
Cost and Financial Assistance
Most insurance plans, including Medicaid, cover PEP. If you have insurance, your out-of-pocket cost depends on your plan’s deductible and copay structure. Co-payment assistance programs from the drug manufacturers can lower or eliminate what you owe for the medications specifically. These programs offer between $5,000 and $7,500 per year in assistance depending on the drug.
If you don’t have insurance, patient assistance programs can provide the medications at no cost. Gilead, which makes one of the core PEP drugs, offers a patient assistance program for people earning up to 500% of the federal poverty level. Keep in mind that these pharmaceutical programs typically cover only the cost of the medication itself, not the clinic visit or lab work. For those expenses, community health centers often use sliding-scale fees based on income, and emergency rooms are required to treat you regardless of ability to pay.
If you were sexually assaulted, many states cover the full cost of PEP through victim compensation programs. Hospital social workers can help you navigate this.
Transitioning to PrEP
If the exposure that led you to PEP reflects an ongoing risk in your life, your provider will likely discuss switching to PrEP once the 28-day course is complete. PrEP is a daily pill (or a long-acting injection given every two months) that prevents HIV before exposure happens. It’s far more practical than relying on PEP after the fact, and it’s over 99% effective when taken consistently.