Something happened — what is my risk?
If you have had a recent sexual encounter you are concerned about, this guide will help you understand your risk, what action to take, and when to get tested.
Concerned about HIV? PEP must be started within 72 hours.
Post-Exposure Prophylaxis (PEP) is a course of HIV medication that can prevent infection if started promptly after a high-risk exposure. Every hour counts. Go to your nearest A&E or sexual health clinic immediately.
Learn about PEP and HIV exposurePEP window — time matters
If you had a high-risk HIV exposure, this timeline shows when PEP can be prescribed.
Ideal window
Start PEP as soon as possible — within 24 hours gives the best outcomes.
Still effective
PEP remains highly effective. Do not delay — seek medical attention today.
Last chance
This is the outer boundary. PEP may still be started but should not be delayed further.
PEP not available
PEP is not recommended beyond 72 hours. Discuss other options with a clinician.
Risk by type of exposure
These risk levels are generalisations. Individual circumstances, vaccination status, and partner status all affect actual risk.
Unprotected vaginal sex
Moderate-high riskVaginal intercourse without a condom carries a meaningful risk of transmission for chlamydia, gonorrhoea, syphilis, herpes, HPV, and — to a lesser degree — HIV.
STIs to consider testing for
When to test
2 weeks minimum for most bacterial STIs; 45 days for HIV 4th gen.
Unprotected anal sex (receptive)
Higher riskReceptive anal intercourse carries the highest per-act HIV transmission risk of any sexual activity. Risk for gonorrhoea, chlamydia and syphilis is also significant.
STIs to consider testing for
When to test
45 days for HIV (4th gen); 2 weeks for bacterial STIs.
Consider PEP if within 72 hours
Unprotected anal sex (insertive)
Moderate riskThe insertive partner in anal sex has a lower — but not negligible — HIV risk. Risk for gonorrhoea, syphilis and herpes remains relevant.
STIs to consider testing for
When to test
45 days for HIV (4th gen); 2 weeks for bacterial STIs.
Consider PEP if within 72 hours
Unprotected oral sex
Lower riskOral sex carries a much lower risk than penetrative sex for most STIs. Gonorrhoea of the throat (pharyngeal gonorrhoea) is the most common concern, alongside herpes and syphilis.
STIs to consider testing for
When to test
2 weeks for gonorrhoea; individual assessment for others.
Condom broke or slipped
Moderate riskA single incident of condom failure is considered a lower-risk event than unprotected sex, but still warrants assessment — particularly if the partner's status is unknown.
STIs to consider testing for
When to test
Same as unprotected sex guidance above.
Sex with a known positive partner
Variable — assess individuallyRisk depends heavily on the specific infection, whether treatment is in place (e.g. HIV Undetectable = Untransmittable), and protective measures used. Individual assessment is strongly recommended.
STIs to consider testing for
When to test
Seek specialist advice promptly.
What to do after a potential exposure
- 1
Assess your HIV risk first
If the encounter carries a HIV risk and happened within the last 72 hours, your first priority is accessing PEP. Go to A&E or call an emergency sexual health line now.
- 2
Note the timing of the exposure
Write down the date and approximate time. Many STI tests have a minimum testing window — testing too early produces unreliable results.
- 3
Use our Exposure Checker tool
Our interactive tool asks structured questions about the encounter and provides a personalised recommendation for testing and timelines.
- 4
Book a sexual health appointment
Most sexual health clinics offer same-day or next-day appointments for people who have had a recent risk exposure. You do not need a GP referral.
- 5
Avoid further unprotected sex until tested
If an infection is present, you may be infectious even before symptoms appear. Protecting partners until you have a result is important.
Get a personalised exposure assessment
Answer a few questions and we will guide you through your next steps.
Use Exposure Checker