The key STI, HIV and contraception guidelines are linked below.

BASHH guidelines on the management of STIs
RCGP / BASHH guidelines for managing STIs in primary care

BHIVA guidelines on Post-Exposure Prophylaxis for HIV (PEP)

BHIVA guidelines on the management of HIV
MedFASH guidelines for managing HIV in primary care

FSRH guidelines on contraception

More specific guidelines can be found on individual pages.