PEP: What to Do After a Possible HIV Exposure

If you think you may have been exposed to HIV, the first step is care, not certainty. You do not need to work out your exact risk alone before asking for help.

What PEP is, in plain language

PEP stands for post-exposure prophylaxis. “Post-exposure” means after a possible exposure; “prophylaxis” means prevention. HIV PEP uses antiretroviral medicines to help prevent HIV from establishing an infection in someone who does not already have HIV. ³

PEP is for an urgent, recent situation, not a daily long-term prevention plan. PrEP, or pre-exposure prophylaxis, is a different approach used before possible future exposures. Someone may appropriately need PEP now and then move to PrEP afterward. ¹

Doxy-PEP is not HIV PEP. Doxy-PEP uses an antibiotic to help prevent certain bacterial sexually transmitted infections in eligible people; it does not replace the antiretroviral medicines used for HIV PEP. ²¹

The first hours: what to do

You can say: “I may have been exposed to HIV, and I need a PEP assessment. The exposure was about ___ hours ago.” Be as accurate as you can about timing and what happened, but do not postpone care because you do not know every detail.

CDC recommends rapid assessment and starting the first dose without waiting for laboratory results when PEP is indicated. An initial blood test is part of care, but getting every result back should not become a reason to miss the prevention window. ¹

If one service cannot assess you or provide medication promptly, ask where you can receive immediate care. Before leaving, confirm how you will obtain the first dose and the rest of the course; a prescription alone does not guarantee that a nearby pharmacy has it. CDC identifies medication access and pharmacy barriers as important parts of PEP care. ¹

If more than 72 hours have passed, still seek care. Routine PEP initiation after that point is not supported by sufficient evidence, but HIV testing, a follow-up plan, other exposure-related care, and discussion of PrEP remain important. Do not interpret “outside the PEP window” as “nothing can be done.” ¹

When PEP may be appropriate, and when it is not

A clinician considers the type of exposure, timing, the other person's HIV status when known, and whether they have sustained viral suppression. If their HIV status is unknown, PEP is assessed case by case; “unknown” does not automatically mean either “safe” or “HIV is present.” ¹

Examples that warrant prompt assessment include a condom breaking during sex, sharing injection equipment, sexual assault, or a needlestick or other qualifying blood exposure. Not every event in these categories requires PEP; the details determine the recommendation. ²¹

Ordinary contact with non-bloody saliva, sweat, tears, or urine is not an indication for HIV PEP. A clinician can explain why a particular contact does or does not present an HIV risk without dismissing your concern. ³

What if the other person is undetectable?

A person living with HIV who achieves and maintains an undetectable viral load does not transmit HIV through sex. That is U=U, and it should not be undermined by suggesting that every sexual encounter with someone living with HIV requires emergency medication. ⁴

The PEP assessment should use reliable, available information about sustained viral suppression. If that information is uncertain, do not spend the prevention window trying to investigate it yourself; let the clinician assess the situation promptly. The sexual-transmission evidence should not simply be applied to a needlestick or shared-injection exposure. ¹

What if I already take PrEP or already live with HIV?

People taking PrEP as prescribed usually do not need PEP, but missed doses, the type of PrEP, and timing can change the assessment. Tell the clinician exactly what you have taken, including any recent long-acting injection. ³¹

PEP is not the treatment plan for someone already living with HIV. A new HIV diagnosis needs a complete ongoing treatment plan and prompt linkage to care, not simply a 28-day prevention course. ³⁴

What happens at the first visit

The clinician will review the exposure and arrange an HIV blood test. A negative test today cannot rule out HIV from an exposure that happened only hours ago. It provides a starting point; follow-up testing is still needed. ¹

Depending on the situation, care can also include kidney and liver tests, hepatitis B and C testing, other STI testing, and a pregnancy test. Hepatitis B vaccination or other preventive care may be needed separately; HIV PEP is not a complete prevention package for every infection or for pregnancy. ¹

Tell the clinician about prescriptions, supplements, antacids, vitamins, and any kidney or liver conditions. Some combinations affect how PEP medicines work, so the regimen should be chosen for you rather than borrowed from someone else. ¹

Pregnancy or breastfeeding does not automatically rule out PEP. These situations need prompt, individualized counseling about the exposure, medication choice, testing, and infant-feeding considerations. ¹

After sexual assault, you deserve confidential, trauma-informed care that addresses your priorities. PEP can be one part of that care alongside other medical needs and support; CDC recommends tailoring services to the person and the circumstances. ¹

Taking PEP for 28 days

The recommended course is 28 days of a three-drug HIV regimen. The number of medicines is not necessarily the number of pills: some options combine several medicines in one tablet. CDC's 2025 recommendations include updated preferred regimens, so an older medication list should not be treated as the only option. ¹

Take the prescribed doses on schedule and arrange the entire course. If you receive only a starter supply, confirm before it runs out how the remaining medicine will reach you. Phone reminders, a calendar, or linking the dose to an established daily routine can help. ¹

If you miss a dose, vomit after taking it, or cannot obtain the next supply, contact the prescriber or pharmacist promptly for instructions specific to your medication. Do not invent a catch-up schedule, double doses on your own, or assume the whole course is pointless.

Nausea, diarrhea, headache, or fatigue can occur, depending on the medicines. Side effects can often be managed; contact the care team rather than quietly stopping treatment. Seek urgent help for a severe reaction or if you feel seriously unwell. ¹²

If you have chronic hepatitis B, make sure the clinician plans for the end of PEP as well as the beginning. Some PEP medicines also suppress hepatitis B, and stopping them can trigger a hepatitis flare in someone with that infection. ¹

Follow-up: finishing the tablets is not the last step

CDC recommends early follow-up within 24 hours to confirm that you obtained the medicine and can take it. That contact can be remote or in person; it is an opportunity to fix access and side-effect problems before they interrupt the course. ¹

The usual follow-up testing schedule includes checks around 4–6 weeks and 12 weeks after the exposure. CDC recommends laboratory antigen/antibody testing plus an HIV nucleic acid test, which looks for the virus; the clinician may tailor the interim visit in some circumstances. ¹

Ask for actual calendar dates before leaving. The detailed CDC text also describes timing from PEP initiation, which may be a few days after exposure, so the care team should set the exact dates rather than leaving you to count them alone. ¹

PEP medicines can temporarily affect how soon HIV becomes detectable. A negative early test is reassuring but does not replace the final follow-up test; stay connected with care even when you feel well. ¹

During follow-up, discuss ways to prevent new exposures, such as condoms and sterile injection equipment, and follow the clinician's advice about blood donation and other precautions. PEP is highly effective when taken as prescribed, but starting it is not a guarantee that follow-up is unnecessary. ¹

Getting PEP when cost or access is a barrier

Tell the clinician immediately if you are uninsured, cannot afford a copayment, lack transport, or cannot get to an open pharmacy. Depending on the circumstances, help may come through insurance, medication-assistance programs, workplace coverage, or sexual-assault assistance resources. Eligibility and the costs covered vary; do not assume all visits, tests, and medicines will automatically be free. ²¹

Ask the care team to help resolve access urgently rather than sending you away with a list of numbers. CDC notes that some manufacturer medication-assistance requests can be handled urgently, but a licensed clinician may need to complete the request. ²³

For a possible workplace exposure, report it through your workplace's exposure process and seek immediate medical attention. Occupational exposures have their own assessment pathway; paperwork should not delay care. ²

After PEP: plan the next step without judgment

If future exposures are possible, ask about moving directly from PEP to PrEP. CDC supports an immediate transition when appropriate, with the required HIV assessment and continued follow-up testing rather than an unnecessary gap in prevention. ¹

Needing PEP is not a moral failing, and needing it more than once is not a reason to withhold respectful care. The useful question is what combination of prevention, access, and support will work for your life.

A checklist you can use today

• Timing: When did the exposure happen?
• Access: Where will I get the first dose, and is the pharmacy open?
• Supply: Do I have all 28 days, or a clear plan for the rest?
• Medication review: Have I shared my PrEP history, medicines, supplements, and relevant health conditions?
• Troubleshooting: Who do I call after hours about a missed dose, side effect, or supply problem?
• Testing: What are my exact follow-up dates?
• Other care: Do I need hepatitis vaccines, other STI care, pregnancy-related care, or support after assault?
• Next step: Would PrEP make sense after PEP?

Keep the urgent message simple: ask for an assessment now if the possible exposure was within 72 hours. You can read the rest of this guide after care is underway. ¹