References UK clinical guidance from the NHS, the British HIV Association (BHIVA), and the British Association for Sexual Health and HIV (BASHH). Last updated: April 2026.
Post-exposure prophylaxis (PEP) is a 28-day course of HIV medication taken after a possible exposure to prevent infection. It must be started within 72 hours — the sooner the better. PEP is available free at NHS sexual health clinics and A&E departments. It’s highly effective when started promptly.
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When PEP Is Needed
| Situation | Action |
|---|---|
| Condomless sex with HIV+ partner (not undetectable) | Seek PEP |
| Condom broke with unknown-status partner | Assess risk; PEP may be indicated |
| Sexual assault | PEP offered routinely |
| Needlestick injury | Occupational health assessment |
| Shared injecting equipment | Seek PEP |
How PEP Works
- 28-day course of antiretroviral drugs
- Must start within 72 hours (ideally within hours)
- Follow-up HIV testing at 4 weeks and 3 months
- Free on NHS
Where to Get PEP
- Sexual health clinics (during hours)
- A&E (out of hours)
- Tell triage you need PEP — they’ll prioritise
Side Effects
- Nausea (common, usually settles)
- Fatigue
- Headache
- Diarrhoea
Read more: PrEP and PEP | Needlestick injuries | When to go to A&E
Frequently Asked Questions
How long do I have to start PEP?
Within 72 hours — sooner is much better.
Is PEP 100% effective?
Very high but not 100%. Starting early maximises effectiveness.
Can I get PEP from a GP?
Usually not — sexual health clinics or A&E provide it.
Related reading
- Are HIV Tests Accurate If You're on PrEP, PEP or ART?
- Choosing the Right PrEP Drug: Truvada vs Descovy
- Pre-Exposure Prophylaxis (PrEP) for HIV
- PrEP and Sexually Transmitted Infections
- PrEP Benefits, Truvada Side Effects and Risks
Sources
- NHS — Sexual health conditions
- BASHH — UK clinical guidelines for STI management
- British HIV Association (BHIVA) — HIV treatment guidelines
- Terrence Higgins Trust — sexual health information
- UK Health Security Agency — STI surveillance data
Steve Page is a recognised expert on Sexually Transmitted Diseases (STDs) and STD treatments, having published numerous articles in peer-reviewed journals and presented his research at conferences around the world. He has an in-depth understanding of the latest medical research on STDs, and is an advocate for the development of new treatments and protocols to improve the health of those affected. In addition to his research, he has dedicated his career to understanding the causes and symptoms of STDs, as well as how to best treat those impacted.
