PrEP
On-demand PrEP (2-1-1): the schedule, simply explained
How to take PrEP on the 2-1-1 schedule, who it is validated for, what to do with repeated sex or a missed dose, and how to organise your follow-up.
By heatmeUp teamUpdated 6 min read
ⓘ Informational article, currently being reviewed by a healthcare professional.
PrEP (pre-exposure prophylaxis) is a treatment taken by HIV-negative people to avoid getting HIV. Taken properly, it is highly effective. It can be taken continuously, or “on demand” following a schedule called 2-1-1. Here is how it works.
PrEP in a nutshell
PrEP usually relies on a pill combining two antiretrovirals (tenofovir disoproxil and emtricitabine). It works only against HIV: it does not protect against other sexually transmitted infections (syphilis, chlamydia, gonorrhoea…) or hepatitis, which is why regular testing still matters.
The 2-1-1 schedule, step by step
The idea: a double dose before sex, then one dose a day for two days.
| When | How many |
|---|---|
| Between 2 and 24 hours before the first sex | 2 pills |
| 24 hours after the first dose | 1 pill |
| 24 hours later (48 h after the first dose) | 1 pill |
If you keep having sex on the following days, continue with 1 pill every 24 hours until 2 days after the last sex (that is, two doses after that last time).
Who is this schedule validated for?
The on-demand schedule has been studied and validated for anal sex, notably among men who have sex with men. It is not suitable in several situations:
- vaginal or front-hole sex: the tissues involved take longer to be protected, so daily PrEP is recommended;
- chronic hepatitis B: repeatedly stopping and restarting treatment can trigger hepatitis flares;
- any situation where your doctor considers continuous PrEP safer.
The best schedule for you is chosen with you during the prescription appointment.
Restarting after a break
If you stop and restart PrEP, your first dose depends on how long it has been since your last one. According to French recommendations, if your last dose was less than a week ago, you can restart with 1 pill; beyond that, start again with 2 pills. If in doubt, assume a double dose is needed and check with your healthcare professional.
What if I miss a dose?
Take the missed pill as soon as possible, then get back to your usual rhythm. If a missed dose may have affected your protection during sex, talk to a healthcare professional quickly.
Medical follow-up
PrEP is prescribed after a check-up: HIV test, hepatitis and STI screening, and kidney function assessment. Follow-up visits then take place roughly every 3 months, with new tests. In France, it can be prescribed by a GP, a free sexual health centre (CeGIDD) or a hospital, and is covered by national health insurance. Elsewhere, check with your local sexual health services.
Tracking on-demand PrEP with heatmeUp
In heatmeUp’s health module, choose the On demand mode:
- enter your first dose and the app reminds you of the next ones;
- see a theoretical protection window calculated from your doses;
- if you have sex again, the cycle is extended automatically;
- your doses (taken, missed, planned) show up in your health calendar.
Everything stays on your phone. And of course, the app is a memory aid: it does not replace your doctor’s advice.
Sources
- World Health Organization (WHO) — HIV pre-exposure prophylaxis
- Haute Autorité de Santé (HAS, France) — PrEP recommendations
- AIDES — PrEP guide
- Centers for Disease Control and Prevention (CDC) — PrEP
ⓘ This guide is for information only and does not replace medical advice. If in doubt, talk to a healthcare professional.