Once you have started taking daily PrEP, it takes seven days for the drug to reach maximum levels in your rectal tissue. That means it will take one week to give you full protection for anal sex. It takes 21 days for PrEP to reach maximum levels in vaginal tissue. If you have a vagina, that means it will take three weeks to give you full protection for vaginal sex.
While you’re waiting for PrEP to become effective, using condoms for anal and vaginal sex will protect you from HIV.