---
title: "PEP (Post-Exposure Prophylaxis) After Sex: What to Do in the First 72 Hours"
description: "Unsure whether you need PEP after sex? This guide explains when it is recommended, where to get it in the UK and the USA and what it costs."
url: https://gay-blog.tomrockets.com/en/pep-hiv/
date_published: 2023-07-24
date_modified: 2026-10-14
---
# PEP (Post-Exposure Prophylaxis) After Sex: What to Do in the First 72 Hours

## Inhaltsverzeichnis

- [Where to get PEP straight away in the UK and the USA](#h-where-to-get-pep-straight-away-in-the-uk-and-the-usa)
- [How soon PEP should start](#h-how-soon-pep-should-start)
- [When PEP is recommended and when it is not](#h-when-pep-is-recommended-and-when-it-is-not)
- [What happens at the clinic and during the 28 days of PEP](#h-what-happens-at-the-clinic-and-during-the-28-days-of-pep)
- [Side effects and missed doses of PEP](#h-side-effects-and-missed-doses-of-pep)
- [PEP in the UK and the USA at a glance](#h-pep-in-the-uk-and-the-usa-at-a-glance)
- [PEP and PrEP](#h-pep-and-prep)

PEP, short for post-exposure prophylaxis, means taking HIV medicines very soon after a possible exposure to HIV. The aim is to prevent the virus from taking hold in your body, says the US website HIV.gov. In the USA, the 2025 guidelines of the Centers for Disease Control and Prevention (CDC) recommend giving the first dose as soon as possible. It should ideally come within 24 hours and no later than 72 hours after exposure.

## Where to get PEP straight away in the UK and the USA

PEP is available in the UK from sexual health clinics or emergency departments. An emergency department, also called A&E ([accident](https://gay-blog.tomrockets.com/en/anal-sex-accident/ "accident") and emergency), is the part of a hospital where people get urgent help. The patient guide of the British Association for Sexual Health and HIV (BASHH) says to tell the staff you think you may need PEP. The staff will then make sure you are seen as soon as possible, the guide says.

If the sexual health clinic is closed after a sexual exposure, the BASHH patient guide says to go to your nearest emergency department. Large emergency departments are open 24/7. PEP is not normally available from GPs (family doctors) in the UK, according to the HIV charity Terrence Higgins Trust.

The US website HIV.gov says to contact a health care provider immediately if you think you were recently exposed to HIV. Or go to an emergency room or an urgent care clinic right away. An urgent care clinic is a walk-in clinic for problems that need attention quickly but are not life-threatening. HIV.gov also says pharmacists can prescribe PEP in some states.

## How soon PEP should start

The UK guideline led by BASHH (2021) says PEP should start as soon as possible after the exposure. It should preferably begin within 24 hours, and can be considered up to 72 hours. BASHH does not recommend starting PEP beyond 72 hours after the exposure.

In the USA, the CDC calls exposure to HIV a medical emergency. According to the CDC, available clinical evidence suggests that the shorter the time to starting PEP, the greater the likelihood of preventing HIV. The CDC also says that the evidence is insufficient to recommend starting PEP later than 72 hours after an exposure.

If the exposure was over 72 hours ago, the UK’s National Health Service (NHS) says a GP or sexual health professional can offer HIV testing.

## When PEP is recommended and when it is not

PEP is recommended or not depending on whether the partner has HIV, on his viral load and on the kind of sex you had. Viral load means the amount of HIV in the blood, measured in copies of the virus per millilitre of blood (copies/mL). An undetectable viral load means the amount of virus in the blood is too low for tests to detect.

In the UK, BASHH recommends PEP after receptive or insertive [anal sex](https://gay-blog.tomrockets.com/en/fucking-anal/ "anal sex") with a partner who has HIV and an unknown or detectable viral load.

The UK guideline recommends PEP after receptive anal sex if the partner’s HIV status is unknown and he is from a high-prevalence group. It gives MSM (men who have sex with men) as an example of such a group. After insertive anal sex with such a partner, the guideline says PEP should be considered.

The guideline does not recommend PEP if the partner has been on HIV treatment for at least 6 months with an undetectable viral load. That means undetectable at the last test and within the last 6 months, with good reported adherence to the treatment. Even if you believe the partner is undetectable, BASHH encourages a formal PEP assessment and a check of his HIV details. If there are any doubts, the guideline says PEP should be given.

In general, the BASHH guideline does not recommend PEP after oral sex, with or without [ejaculation](https://gay-blog.tomrockets.com/en/forced-ejaculation/ "ejaculation"), because the risk is very low. The guideline also does not recommend PEP after [semen](https://gay-blog.tomrockets.com/en/produce-semen/ "semen") in the eye, because the risk is negligible.

In the USA, the CDC recommends PEP after anal sex without a [condom](https://gay-blog.tomrockets.com/en/jerking-with-a-condom/ "condom") if the partner has HIV and a detectable viral load. The CDC also recommends PEP if the partner has HIV and it is unknown whether he is virally suppressed. If it is unknown whether the partner has HIV, the CDC leaves it to a case-by-case assessment by the clinician. With an intact condom, the CDC does not recommend PEP.

The CDC does not routinely recommend PEP if the partner has sustained viral suppression, meaning HIV treatment for more than 6 months, taken consistently. It also means every viral load test in the last year was under 200 copies/mL or undetectable, the latest within 1 to 2 months of the exposure.

The CDC does not recommend PEP for people taking PrEP as recommended. PrEP, short for pre-exposure prophylaxis, is medicine taken to prevent HIV. PEP may be considered, for example, after recently starting PrEP or after missed doses.

## What happens at the clinic and during the 28 days of PEP

PEP lasts 28 days in both countries, according to HIV.gov in the USA and the BASHH guideline in the UK. HIV.gov describes PEP as a course of daily HIV medicines. It is important to take all the doses as prescribed to give PEP the best chance of working.

The first clinic visit in the UK includes an HIV test and blood tests of your kidney and liver, BASHH says. You have a hepatitis B test if you are not known to be protected, and after sex also tests for [chlamydia](https://gay-blog.tomrockets.com/en/chlamydia-infection/ "chlamydia"), [gonorrhoea](https://gay-blog.tomrockets.com/en/gonorrhoea-symptoms/ "gonorrhoea") and syphilis. In the USA, the CDC recommends an HIV test at the first visit, plus routine blood tests and a hepatitis B test. The CDC says the first dose should not wait for pending laboratory results; BASHH says starting PEP should not wait for blood results.

## Side effects and missed doses of PEP

PEP is usually safe, and most people in the UK who take it have no side effects, the patient guide from BASHH says. Commonly reported problems, affecting up to 1 in 10 people, include feeling sick, a lack of energy, dizziness and diarrhoea. Others are loss of appetite, trouble sleeping, headache and stomach ache. If any of these problems happen, they are usually mild and usually do not last very long, according to the guide.

If side effects cause a big problem or make it hard to carry on, the guide says to phone the sexual health clinic. Ask for advice before deciding to stop.

A skin rash or a flu-like illness while taking PEP might be an allergic reaction to the medicine, the BASHH patient guide says. The same symptoms sometimes happen after [HIV infection](https://gay-blog.tomrockets.com/en/hiv-symptom/ "HIV infection"). Contact the clinic as soon as possible if this happens while taking PEP or in the 6 weeks after finishing it.

If you forget a dose of PEP in the UK, the BASHH patient guide tells you what to do:

- Take the missed dose as soon as you remember it.
- If it is already time for your next dose, skip the missed dose and go back to your regular schedule.
- Do not take a double dose to make up for a forgotten dose.
- If more than 48 hours have passed since your last dose, contact your clinic as soon as possible.

The CDC says PEP in the USA may cause side effects such as nausea in some people. In almost all cases, these side effects can be treated and are not life-threatening. HIV.gov advises talking to your health care provider if a side effect bothers you or does not go away.

## PEP in the UK and the USA at a glance

PEP differs between the UK and the USA on cost, how the medicine is given, the final HIV test and the move to PrEP.

|  | UK | USA |
| --- | --- | --- |
| Cost | Free from sexual health clinics (GOV.UK) | In many states, health insurance including Medicaid covers PEP; without insurance, assistance programmes can provide free or low-cost medicines (HIV.gov) |
| How the medicine is given | BASHH recommends the full course at the first visit unless there are operational reasons, as starter packs can make people stop early. With a 3 to 5 day starter pack, the BASHH patient guide says to get the full 28-day course from a sexual health clinic before the pack runs out. | The full supply, or a starter pack (typically 3 to 5 days) with a plan for the rest, or a prescription (CDC) |
| Final HIV test | Can be done 45 days after finishing the course, at least 10.5 weeks after exposure for a completed 28-day course; after sex, 12 weeks after exposure (BASHH) | An interim HIV test 4 to 6 weeks after exposure, and the final HIV test 12 weeks after exposure (CDC) |
| Moving on to PrEP | BASHH recommends moving straight on to PrEP for people coming for PEP who are likely to stay at high risk | An immediate switch to PrEP might help if exposures may repeat or continue (CDC) |

## PEP and PrEP

HIV.gov says PEP should be used only in emergencies and does not replace regular prevention. If you may be exposed to HIV often, HIV.gov advises talking to your provider about PrEP; read [how PrEP protects you before sex](https://gay-blog.tomrockets.com/en/hiv-prep/).

While you are taking PEP in the USA, HIV.gov advises using other prevention methods as well, such as condoms.

## FAQ

### How well does PEP work?

PEP is likely to be highly effective, the UK guideline from BASHH says. This is the case when it is started promptly, taken as prescribed and further exposures are avoided. In the USA, HIV.gov says PEP is effective in preventing HIV infection when it is taken correctly, but it does not work in every case.

### Can PEP be stopped if my partner tests negative?

In the UK, the clinic can stop PEP if your partner agrees to a laboratory HIV test and tests negative, BASHH says. Testing your partner should not delay starting it. The CDC says PEP in the USA should not be delayed while your partner’s HIV status is checked. It should be stopped if your partner is found not to have HIV.

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