How do I take PrEP effectively? PrEP is only effective, when taken both before and after sex. There are two ways you can take PrEP, depending on your circumstances and how often you have sex: Daily dosing – continuous use of PrEP every day. On-demand dosing or event-based dosing – see our FAQ about on-demand or event-based doing for more information. See also our FAQ about vaginal sex and women.