Daily vs on-demand (2-1-1) PrEP: which is right for you?
How daily PrEP and on-demand 2-1-1 PrEP work, who each one is for, exactly how to take the 2-1-1 doses, and the mistakes to avoid.
There are two ways to take oral PrEP: one tablet every day, or “on-demand” PrEP, taken only around the times you have sex. Both use the same tablet (emtricitabine and tenofovir, such as Tenof-EM). Which one suits you depends on who you are and how predictable your sex life is.
Quick answer: Daily PrEP works for almost everyone. On-demand (2-1-1) PrEP is for cisgender men (whatever their partner’s gender) and for people assigned male at birth who are not taking feminising hormones, when sex can be planned at least 2 hours ahead. It is not suitable for anyone who has receptive vaginal or front-hole sex, people who inject drugs, or people with hepatitis B.
Daily PrEP
Take one tablet once a day, at about the same time each day. After about 7 days of daily tablets you are protected. Keep taking it every day for as long as you might be exposed. Before stopping, ask the doctor how long to keep taking it after your last possible exposure.
Missed a dose? Take it as soon as you remember, but never more than 2 tablets in one day. If you have missed more than 2 days, speak to our doctor before restarting, and ask about PEP if you may have been exposed.
Daily PrEP suits almost everyone (unless kidney function is too low), and it is the right choice for:
- women, and anyone who has receptive vaginal or front-hole sex
- people who inject drugs
- trans people taking feminising hormones
- people with hepatitis B
- anyone whose sex is frequent or hard to predict
On-demand (2-1-1) PrEP
On-demand PrEP, also called event-driven PrEP, is taken like this:
- 2 tablets together, 2 to 24 hours before sex
- 1 tablet 24 hours after the first dose
- 1 tablet 48 hours after the first dose
If you keep having sex over several days, continue taking one tablet every 24 hours until 2 days after the last time you had sex. Ask our doctor how to restart if your next occasion comes soon after the last one.
How to choose
| Daily PrEP | On-demand (2-1-1) | |
|---|---|---|
| Who it’s for | Almost everyone at risk | Cisgender men, and people assigned male at birth not taking feminising hormones |
| Best when | Sex is frequent or unpredictable | Sex is occasional and can be planned 2+ hours ahead |
| Tablets | About 30 a month | 4 for a single occasion |
| Main risk | Missed days | Getting the timing wrong |
| Not suitable | Low kidney function, or HIV-positive | Receptive vaginal or front-hole sex, injecting drugs, hepatitis B |
Common mistakes
- Taking only 1 tablet before sex the first time, instead of 2.
- Skipping the two doses after sex. They matter as much as the ones before.
- Switching to on-demand PrEP when you have hepatitis B. Starting and stopping can make hepatitis B flare up.
- Stopping daily PrEP the day after sex. Ask the doctor how long to continue after your last possible exposure.
Talk to the doctor before switching
Whichever way you take it, you still need an HIV test every 3 months and the other PrEP check-ups. Our doctor reviews every PrEP order and can help you decide which way of taking it suits you.
6. Questions people ask
Can women use on-demand PrEP?
No. For receptive vaginal or front-hole sex, PrEP needs to be taken daily, because the medicine takes longer to build up in vaginal tissue. On-demand 2-1-1 PrEP is for cisgender men and people assigned male at birth who are not taking feminising hormones.
What if I forget the doses after sex?
Take the missed tablet as soon as you remember, and talk to our doctor. If you may have been exposed without enough protection, PEP may be needed within 72 hours.
How many tablets do I need for on-demand PrEP?
At least 4 for one occasion: 2 before sex, then 1 tablet 24 hours and 1 tablet 48 hours after the first dose. A box of 30 tablets covers several occasions.
