You Had Unprotected Sex — A Plan for the Next 72 Hours and Beyond

What to do first

The single most useful thing after unprotected sex is to sort the response by time, because two of the options expire. The first question is whether HIV could have been a factor — if so, HIV PEP is a medication that must be started as soon as possible and within 72 hours of the exposure to work 1Ref 1Centers for Disease Control and Prevention (2024).Clinical Guidance for PEP.That HIV PEP must be started as soon as possible and within 72 hours of exposure, is taken for 28 days, and is for emergency/one-time exposures.. The second, if pregnancy is possible, is emergency contraception, which is also more effective the sooner it is taken.

The order that helps. Handle the time-limited decisions first — the ones on the 72-hour clock — then move to testing, which happens on a longer timeline. Panic tends to reverse this, sending people for a test the next morning that cannot yet detect anything, while the genuinely urgent window quietly closes.

A realistic sense of risk. Not every encounter carries every risk. The chance of HIV, other STIs, or pregnancy depends on the specific situation, a partner's status, and what kind of sex occurred. The point of a plan for what to do after unprotected sex is not to assume the worst — it is to make sure the time-sensitive doors are not missed while there is still time to use them.

Where to go depends on the clock. If a time-sensitive option is in play, an emergency department, urgent care, or sexual-health clinic can act tonight; if it is purely about testing, a regular appointment in the right week is fine. Sorting which bucket you are in is the first real decision, and it is one a clinician can help make over the phone if you are unsure.

The 72-hour clock: HIV PEP

HIV PEP — post-exposure prophylaxis — is a course of HIV medication that can prevent infection after a possible exposure, and it is strictly time-limited. It must begin as soon as possible and no later than 72 hours after the exposure, and it is taken as a 28-day course 1Ref 1Centers for Disease Control and Prevention (2024).Clinical Guidance for PEP.That HIV PEP must be started as soon as possible and within 72 hours of exposure, is taken for 28 days, and is for emergency/one-time exposures.. The first dose is ideally within 24 hours; every hour earlier improves the odds 2Ref 2Centers for Disease Control and Prevention (2025).Antiretroviral Postexposure Prophylaxis After Sexual, Injection Drug Use, or Other Nonoccupational Exposure to HIV - CDC Recommendations, United States, 2025.That the first PEP dose is ideally within 24 hours, PEP includes a baseline HIV test and follow-up at about 4-6 and 12 weeks, and that people with ongoing risk should plan a transition to PrEP..

Where the pep window is handled. Because it is urgent and often needed after hours, PEP is available through emergency departments, urgent care, and sexual-health clinics — the hiv-npep-72-hour-window does not pause for office hours. Someone who thinks HIV was a real possibility does not need to be certain; a clinician assesses the risk and decides whether to start it.

What comes with it. Starting PEP includes a baseline HIV test and follow-up testing, typically around 4 to 6 weeks and again at 12 weeks, and — for anyone with ongoing risk — a conversation about moving from PEP to PrEP for continuous prevention afterward 2Ref 2Centers for Disease Control and Prevention (2025).Antiretroviral Postexposure Prophylaxis After Sexual, Injection Drug Use, or Other Nonoccupational Exposure to HIV - CDC Recommendations, United States, 2025.That the first PEP dose is ideally within 24 hours, PEP includes a baseline HIV test and follow-up at about 4-6 and 12 weeks, and that people with ongoing risk should plan a transition to PrEP.. The pep window is the most important thing on this page precisely because, unlike testing, it cannot be done later.

What if you're past 72 hours? Once the window has closed, PEP is no longer the tool — but the response is not over. The focus shifts to testing on the right schedule and, for anyone with ongoing risk, starting PrEP so the next exposure is already covered 2Ref 2Centers for Disease Control and Prevention (2025).Antiretroviral Postexposure Prophylaxis After Sexual, Injection Drug Use, or Other Nonoccupational Exposure to HIV - CDC Recommendations, United States, 2025.That the first PEP dose is ideally within 24 hours, PEP includes a baseline HIV test and follow-up at about 4-6 and 12 weeks, and that people with ongoing risk should plan a transition to PrEP.. Missing the PEP window is a reason to move toward prevention, not a reason to do nothing.

HIV PEP only works if it starts within 72 hours of the exposure, and sooner is better — this is the one decision on the whole list that expires.

Doxy-PEP for bacterial STIs, if you're eligible

For some people, there is a second after-sex option on a similar clock. Doxy-pep is a single dose of the antibiotic doxycycline taken within 72 hours of sex to lower the risk of three bacterial STIs — syphilis, chlamydia, and gonorrhea 3Ref 3Bachmann LH, Barbee LA, Chan P, et al. (Centers for Disease Control and Prevention) (2024).CDC Clinical Guidelines on the Use of Doxycycline Postexposure Prophylaxis for Bacterial Sexually Transmitted Infection Prevention, United States, 2024.That doxy-PEP is a dose of doxycycline taken within 72 hours after sex to prevent bacterial STIs, recommended mainly for gay and bisexual men and transgender women who had a bacterial STI in the prior year.. It is the doxy pep after sex antibiotic that people increasingly ask about after an exposure.

Who it applies to. Current CDC guidance recommends offering it mainly to gay and bisexual men and to transgender women who have had one of those bacterial STIs in the past year 3Ref 3Bachmann LH, Barbee LA, Chan P, et al. (Centers for Disease Control and Prevention) (2024).CDC Clinical Guidelines on the Use of Doxycycline Postexposure Prophylaxis for Bacterial Sexually Transmitted Infection Prevention, United States, 2024.That doxy-PEP is a dose of doxycycline taken within 72 hours after sex to prevent bacterial STIs, recommended mainly for gay and bisexual men and transgender women who had a bacterial STI in the prior year.. It is not a general after-sex antibiotic for everyone, and it does nothing for HIV or for pregnancy.

How it fits the plan. For an eligible person, doxy-PEP shares the 72-hour urgency with HIV PEP but addresses different infections. For everyone else, it is not part of the immediate response — testing on the normal schedule is. Its full eligibility rules and how it works are covered on their own page.

If pregnancy is possible: emergency contraception

If the encounter could lead to pregnancy, emergency contraception is the other time-sensitive decision, and it is entirely separate from the STI questions. It is more effective the sooner it is used after unprotected sex, which is why it belongs on the same early checklist rather than being put off until later.

Where the details live. How emergency contraception after unprotected sex works, the differences between the available options, and how the morning after pill how it works — including its plan b time window — are covered on a dedicated page, because the timing and the choices deserve their own full explanation. The key point here is only that emergency contraception timing is short, so the decision is worth making early.

Different jobs, different clocks. Emergency contraception and HIV PEP are both time-sensitive, but they do completely different things, and their exact windows differ. Neither substitutes for the other, and a single encounter can call for both, one, or neither.

Common scenarios, and what changes the plan

The right next step depends on the specifics of the encounter — who the partner was, what kind of sex occurred, and whether it was consensual all change the calculation. Working through the most common situations shows how the same 72-hour framework bends to fit each one. A few that people ask about most:

• A condom broke with a partner whose status you don't know. This is a classic reason to weigh HIV PEP quickly, because the 72-hour window is running whether or not you feel any urgency 1Ref 1Centers for Disease Control and Prevention (2024).Clinical Guidance for PEP.That HIV PEP must be started as soon as possible and within 72 hours of exposure, is taken for 28 days, and is for emergency/one-time exposures.. A clinician assesses how much actual risk the encounter carried and decides from there.
• Your partner is known to be HIV-positive. Whether PEP is needed depends on their treatment and viral load, which a clinician can factor in fast; if there is any uncertainty, PEP is firmly on the table 1Ref 1Centers for Disease Control and Prevention (2024).Clinical Guidance for PEP.That HIV PEP must be started as soon as possible and within 72 hours of exposure, is taken for 28 days, and is for emergency/one-time exposures..
• It was oral sex only. It still carries STI risk — chlamydia and gonorrhea can infect the throat and often cause no symptoms, so throat testing may still matter even when nothing feels wrong 6Ref 6Centers for Disease Control and Prevention (2024).About Gonorrhea.That gonorrhea can infect the genitals, rectum, and throat and is often asymptomatic — the basis for extragenital (throat/rectal) testing..
• You were assaulted, or could not consent. This is a situation for emergency care, which can address injuries, HIV PEP, emergency contraception, and — if you choose — evidence collection, together and confidentially.

The common thread. None of these call for guessing alone. Each is something a clinician can triage quickly, and several are on a clock, which is why reaching one sooner beats waiting to see how you feel over the next few days.

After the window: why the testing timeline matters

Testing is the part people rush and get wrong. Right after an exposure, most STI and HIV tests read negative even if an infection is taking hold, because each infection has a window period — the gap between exposure and when a test can reliably detect it. Testing too early produces false reassurance, not a clean bill of health.

HIV is the clearest example. Depending on the test, HIV becomes detectable roughly 10 to 33 days after exposure for a nucleic-acid test, about 18 to 45 days for a lab antigen/antibody test, and as long as 23 to 90 days for a rapid antibody test 4Ref 4Centers for Disease Control and Prevention (2024).Clinical Testing Guidance for HIV.HIV test window periods by test type: nucleic-acid test ~10-33 days, lab antigen/antibody ~18-45 days, and rapid antibody tests ~23-90 days after exposure.. A negative result before the window has passed does not rule the infection out.

How to use the windows. The practical approach is to test at the right time for each infection, and sometimes to test twice — once at a baseline and again after the relevant window closes. A full sti window periods reference — essentially a std window period chart by infection — lays out the timing for each one, so no one ends up testing on the wrong day and trusting the result.

Why a single early test is not enough. Because different infections clear their windows at different times, one negative test soon after an exposure can miss an infection a later test would catch. That is why clinicians often set up a baseline round and a follow-up round rather than a single visit — the follow-up is where a late-appearing HIV result actually shows up 4Ref 4Centers for Disease Control and Prevention (2024).Clinical Testing Guidance for HIV.HIV test window periods by test type: nucleic-acid test ~10-33 days, lab antigen/antibody ~18-45 days, and rapid antibody tests ~23-90 days after exposure..

Which STIs to test for, and when

A reasonable panel after a new exposure covers HIV, chlamydia, gonorrhea, and syphilis, with trichomoniasis and hepatitis depending on the situation. The two most common bacterial STIs are worth understanding, because they usually give no warning at all. Chlamydia is common, frequently silent, and curable — but if left untreated it can cause pelvic inflammatory disease and infertility in women 5Ref 5Centers for Disease Control and Prevention (2024).About Chlamydia.That chlamydia is a common, frequently asymptomatic, curable bacterial STI that can cause pelvic inflammatory disease and infertility if untreated..

Beyond the genitals. Gonorrhea can infect not only the genitals but also the rectum and the throat, and it is often symptom-free at every site 6Ref 6Centers for Disease Control and Prevention (2024).About Gonorrhea.That gonorrhea can infect the genitals, rectum, and throat and is often asymptomatic — the basis for extragenital (throat/rectal) testing.. That matters for testing: an infection in the throat or rectum is missed by a urine sample alone. For men who have sex with men, msm sti screening typically includes those sites — extragenital-testing of the throat and rectum — precisely because a single genital test would miss them.

Timing the panel. Bacterial STIs like chlamydia and gonorrhea can usually be tested for sooner than HIV or syphilis, but retesting after the full window closes is how a delayed infection is caught. A clinician tailors which tests, and which body sites, to the specific exposure rather than running one generic swab.

Lowering the risk going forward

Once the immediate window is handled, the same visit is a good moment to think ahead. For anyone with ongoing risk, guidelines suggest planning a transition from PEP to PrEP — medication that provides continuous HIV prevention rather than a one-time, after-the-fact course 2Ref 2Centers for Disease Control and Prevention (2025).Antiretroviral Postexposure Prophylaxis After Sexual, Injection Drug Use, or Other Nonoccupational Exposure to HIV - CDC Recommendations, United States, 2025.That the first PEP dose is ideally within 24 hours, PEP includes a baseline HIV test and follow-up at about 4-6 and 12 weeks, and that people with ongoing risk should plan a transition to PrEP.. PEP is the emergency brake; PrEP is the seatbelt worn in advance.

Building a routine. Regular STI screening on a schedule, honest conversations with partners about testing, condoms, and vaccination against preventable infections such as HPV and hepatitis together do far more than any single crisis response. Each lowers a different risk, and none of them depends on remembering to act within 72 hours.

The takeaway. After unprotected sex, act on the 72-hour options first, test on the right schedule second, and use the visit to set up prevention third. Fear after an exposure is understandable — but a plan handles it better than panic, and every part of this one is something a clinician can walk through with you.