How to take PrEP

This section discusses different ways that you can take TD/FTC PrEP. *

PrEP is likely to be most effective when both PrEP drugs are at protective levels before you have sex. However, any PrEP, even if late, is better than none.

Drug absorption and dosing options

Your body takes time to absorb drugs. Therefore, PrEP should be taken both BEFORE sex (to let the levels build up) and AFTER sex (to keep levels high).

Also, each drug is different.

FTC (emtricitabine) is absorbed rapidly, giving protection within hours, but levels drop more quickly. 

TD takes up to 24 hours to reach rectal tissue, but it then stays at higher levels for longer. TD levels are lower in vaginal tissue, which is why daily PrEP is needed for women and trans men having frontal sex. On-demand (2:1:1) dosing is very effective for anal sex or for straight men having vaginal sex.

TAF is absorbed more quickly that TD and stays at higher levels for longer, but is only for men and transgender women. Unless you need TAF for medical reasons, it is rarely used in the UK and is not approved in the EU.

You can take TD/FTC PrEP in different ways depending on your circumstances and how often you have sex.

Women, trans and non-binary who want protection from vaginal or front hole sex, need to take daily PrEP at least six days each week. It also takes about a week to reach protective drug levels. This is because PrEP is absorbed differently in vaginal tissue compared to rectal tissue.

2:1:1 dosing is very effective for anal sex or for straight men having vaginal sex. This involves taking two pills 2 to 24 hours before sex as a double dose. Then a single pill 24 hours and 48 hours after the first double dose. 2:1:1 dosing is NOT suitable for women, transgender and non-binary people having vaginal sex or front hole sex. In these cases, the longer lead in of seven days is needed to reach protective levels.


On-demand 2:1:1 dosing: for anal sex (or straight men having vaginal sex)

Men whose only risk is insertive sex (vaginal or anal), can use 2:1:1 dosing.

Please talk to your doctor about the best dose and timing that will be most suitable for you.

* PrEP with TAF/FTC is only approved for daily dosing.

Last updated: 1 February 2022.