Why speed matters
A condom breaking or slipping, sex without a condom with a partner of unknown HIV status, or a used-needle injury leaves many people shocked and unsure what to do first. The most important answer is to seek assessment quickly, because post-exposure prophylaxis (PEP) works best when started early and must begin within 72 hours when indicated.[1]
Knowing the steps in advance reduces panic and avoids losing precious time.
Every hour counts
Prompt assessment helps ensure PEP starts in time.[1] The CDC's 2025 guidance recommends starting as soon as possible, ideally within 24 hours and no later than 72 hours after exposure.[1] Many people lose time searching online, waiting for symptoms or waiting to ask a partner, and miss the window when the medicine works best.
What determines the real risk
The risk from a single event depends on the type of exposure, other prevention used and the partner's viral load; it is not the same as HIV prevalence in the population.[1] Receptive anal sex carries higher risk than other sexual exposures, and sharing needles is also high risk. Your doctor weighs these details to decide whether PEP is needed.
How HIV enters, and how PEP helps
HIV enters through mucous membranes, such as the rectum, vagina or urethra, or through the blood. After it enters, it takes some time before infection becomes permanently established. PEP has to act during this window to stop the virus before it is too late.[1],[2]
This is why you should never wait for symptoms: by the time symptoms of early infection appear, the window for PEP has passed.
What information to bring
This information helps a doctor assess you quickly[1],[2]:
- When it happened, as precisely as possible.
- Type of exposure: anal, vaginal, oral or needle; whether a condom was used, broke or slipped.
- Information about the partner or source, if known, such as HIV status and whether they are on treatment with an undetectable viral load.
- Your current medicines and health conditions.
The doctor will do a baseline HIV test but will not wait for every result before starting indicated treatment, to avoid delay.[1],[2]
What happens next
Start indicated PEP as soon as possible, ideally within 24 hours and no later than 72 hours, and take it for 28 days.[1]
Do not delay for every kidney or liver result. Other blood tests can run alongside but should not hold up the first dose.[1]
If more than 72 hours have passed, PEP is usually not recommended, but you should still seek testing and prevention advice: HIV testing at the right intervals, testing for other STIs, and considering PrEP for the future.[1],[3]
In the meantime, use condoms or avoid sex until follow-up results are known, to avoid passing on infection if it has occurred.
How we care for you at Dr. Kris Clinic
We know the hours after a risk are very stressful. Message LINE @dr.krisclinic straight away to arrange PEP assessment as quickly as possible. Assessment is confidential and judgement-free, in English or Thai, and treatment can start the same day when indicated.
If the clinic is closed at that moment, do not wait for a reply: go to a hospital or service providing PEP immediately, then follow up with us. After PEP, we help plan follow-up testing and consider PrEP if it suits you.
Frequently asked questions
My condom broke. Do I always need PEP?
It depends on the type of exposure and what is known about the partner. Get assessed quickly so a doctor can decide.
It's been more than 72 hours. What can I do?
PEP is usually no longer recommended, but you should still have HIV testing at the right intervals, test for other STIs and talk about PrEP.
Will an HIV test straight after the exposure tell me anything?
It provides a baseline, but cannot show whether this exposure caused infection. Repeat testing at the intervals your doctor advises.
My partner says they're HIV-negative. Do I still need PEP?
It depends on when they were last tested and whether they have had risks since. Your doctor will help assess this.
PEP assessment is urgent; do not wait for symptoms or for the end of a test window.[1] See a doctor within 72 hours, the sooner the better, and if the clinic is closed, go to a hospital that provides PEP immediately.
Talk to a doctor about this
Confidential care in Surat Thani, the mainland gateway to Koh Samui, Koh Phangan and Koh Tao. Tue–Fri 17:00–20:00 · Sat–Sun 10:00–15:00 (UTC+7)
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Dr. Krida Uakridathikarn (Dr. Kris)
Board-certified family physician with certificate training in clinical sexology and sexual medicine. He works at Suratthani Hospital and provides sexual health, hormone and LGBTQ+ inclusive care at Dr. Kris Clinic. Profile and CV
References
- CDC nPEP Recommendations 2025. MMWR 74(RR-1)
- CDC: Getting Tested for HIV; test window periods
- CDC HIV Nexus: Clinical Guidance for PrEP (current page)
Keep reading
Main guide: HIV & STI prevention
PrEP vs PEP: HIV Prevention Before and After Exposure
After Starting PEP: The 28-Day Course and Follow-Up Testing
Daily vs On-Demand (2-1-1) PrEP: Who Can Use WhichThis article is general education, not personal medical advice or a promise of results. Diagnosis and treatment require assessment by a doctor. Content reflects the cited sources as of the update date.