Here's some information about PEP (within 72 hours of exposure):

If you've had unprotected sex with someone with HIV you may need medicine to reduce your risk of becoming HIV+ but this must be started within 72 hours to be effective (HIV PEP or post-exposure prophylaxis).

Anal sex without a condom for men who have sex with men, having a partner from a high-risk country, or sharing drug injecting equipment would also be high-risk and may mean you need PEP within 72 hours. For accessing PEP outside clinic's working hours please go to your nearest A&E unit.

See HIV for more information – you may have no symptoms for years but may be at risk of life-threatening infections and increased cancer risk, all of which can be reduced with treatment. Early HIV infection may sometimes present with a seroconversion illness when you may feel unwell with ‘flu-like symptoms like a rash, sore throat and fever.