What is the difference?
PrEP vs PEP
PrEP and PEP sound almost identical and both use HIV medicines to prevent HIV, so they are easy to mix up. The key difference is timing: PrEP is taken regularly before any possible exposure, while PEP is an emergency course started after one.
General information, not medical advice. For advice about your own situation, talk to a clinician, pharmacist or sexual health clinic.
PrEP
PrEP is medicine taken by HIV-negative people before possible exposure to greatly reduce their chance of getting HIV.
Full entryPEP
PEP is a 28-day course of HIV medicine taken after a possible exposure to HIV to stop the virus from taking hold; it must be started as soon as possible, ideally within 72 hours.
Full entrySide by side
In short
PrEP is a planned, ongoing shield taken before; PEP is a one-off emergency course taken after a possible exposure, as soon as possible.
What they have in common
Both use HIV medicines to stop HIV from taking hold, and neither protects against other STIs or pregnancy.
Sources
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Last reviewed 10 October 2026. Spotted a mistake?