If you have just noticed a PrEP missed dose, take it as soon as you remember if you are within 12 hours of your usual time; if not, skip it and carry on at your normal time, without doubling up.
Most people on PrEP forget a pill at some point. One late or missed tablet on daily PrEP rarely leaves you unprotected, but the rules are different for 2-1-1, and a few situations call for a quick conversation with a doctor. This guide walks through each one so you can decide what to do in the next five minutes.
The short answer for daily PrEP
NHS guidance is simple. If you miss your daily pill, you can still take it as long as it is within 12 hours of when it was due. If more than 12 hours have passed, leave that dose out and take the next one at your usual time.
- Never take two pills to catch up on daily PrEP. A double dose adds no protection.
- For full protection on daily PrEP, the NHS says you need at least six doses in the past seven days.
- If you stop for a week or more, you restart as though you were beginning again.
You can read the full wording in the NHS advice on how and when to take PrEP.
What to do depending on how late you are
The right step after a PrEP missed dose depends on two things: how long ago the pill was due, and whether you take PrEP every day or around sex using 2-1-1. Find your row below.
How late you are and what to do next
| How late | Daily PrEP | 2-1-1 PrEP |
|---|---|---|
| A few hours (up to 12) | Take it now, then back to your usual time | Take it now and keep the next pill on schedule |
| More than 12 hours | Skip it; take the next at the usual time | Take it as soon as you remember and speak to a doctor if you had sex |
| One whole day | Take today’s pill as normal; one pill only | Protection for that episode is uncertain; ask about PEP |
| Two to six days | Restart your daily pill; get advice if you had condomless sex | Not applicable |
| A week or more | Restart as if new, with an HIV test | Not applicable |
If you have vaginal or front-hole sex, steady daily dosing matters more. Drug levels in vaginal tissue take longer to build up, so speak to a doctor sooner if you have missed several pills.
Missed doses on 2-1-1 PrEP
On-demand PrEP has less slack than daily PrEP, because every pill is timed around a specific episode of sex. It is only for cis men who have sex with men and trans women not taking estradiol-based hormones. It is not suitable for vaginal or front-hole sex, or for anyone with hepatitis B.
The schedule is two pills 2–24 hours before sex, one pill 24 hours after the first dose and one pill 48 hours after the first dose. If sex continues, you take one pill every 24 hours until two days after the last sex. Our 2-1-1 PrEP dose calculator works out the exact times for you.
Missed the first double dose
If you had sex without taking the two starting pills beforehand, you cannot rely on 2-1-1 for that encounter. Contact a doctor promptly; PEP may be the better choice if you are still within 72 hours.
Missed the second 2-1-1 dose
A pill that is a few hours late is usually fine: take it as soon as you remember and keep the third pill at 48 hours after your first dose. If you missed the second pill altogether, or realised more than half a day later, talk to a doctor about whether PEP makes sense.
Daily vs 2-1-1 when a pill is late
| Point | Daily PrEP | 2-1-1 PrEP |
|---|---|---|
| Room for error | Fairly forgiving with six of seven doses | Little; each pill matters |
| Take two to catch up? | No | Only the planned starting double dose |
| Who can use it | Anyone it is prescribed for | Cis men who have sex with men and some trans women |
| Best if you often forget | Yes, with reminders | Harder to time |
Common moments people forget
These are the situations people search for most, with the plain answer for daily PrEP.
You forgot to take PrEP yesterday
Take today’s pill at your usual time and carry on. One missed day after a run of regular doses still leaves you well covered. If you have missed several days this week and had condomless sex, get advice.
You missed your PrEP dose by 12 hours
At exactly 12 hours you can still take it. Past that point, skip it rather than squeezing two pills close together. Many people simply move their dosing time a little later so the gap stays even.
You forgot to take PrEP in the morning or last night
If you forgot to take PrEP in the morning and notice by the evening, take it then. If you forgot to take PrEP last night and it is now the next morning, you are usually still inside the 12-hour window. If you missed a PrEP pill or forgot to take PrEP for a day now and then, that matters far less than a regular pattern of gaps.
When a missed pill means you might need PEP
A PrEP missed dose only points towards PEP when your recent pills fall short. PrEP taken unreliably cannot be counted on. You should think about PEP if you had condomless sex or shared injecting equipment and your recent PrEP doses do not meet the rules above.
- You took fewer than six daily pills in the week before sex.
- You started daily PrEP less than seven days ago (21 days for vaginal sex or injecting).
- You had sex on 2-1-1 without the starting double dose, or missed a follow-up pill.
Exposed in the last 72 hours? You need PEP, not PrEP. Ask us about urgent PEP today; it works best the sooner it starts.
After any gap, you may need an HIV test before carrying on. Our guide to the tests you need while on PrEP explains the timing.
How to miss fewer pills
- Link your pill to something you already do every day, such as brushing your teeth.
- Set a repeating phone alarm and keep a spare pill in your bag or wallet.
- When you fly into Bangkok, keep to home time or shift by an hour a day; our PrEP tips for travellers in Thailand cover time zones.
- If you keep missing daily pills, ask whether a different schedule suits you better. Our guide on how to start and stop PrEP safely explains how to switch.
Not sure PrEP is still the right fit? Read who PrEP is designed for, or book a PrEP review with our doctors to talk it through.
Questions people ask
What happens if I miss one day of PrEP?
On daily PrEP, one missed day after regular doses usually leaves you protected. Take your next pill at the normal time and don’t double up.
I missed my PrEP dose by a few hours. Is that OK?
Yes. If you are within 12 hours of your usual time, take it now and carry on as normal the next day.
Should I take two PrEP pills if I missed one?
Not on daily PrEP. The only planned double dose is the two starting pills of 2-1-1, taken before sex.
How many PrEP pills can I miss and still be protected?
The NHS says at least six doses in the past seven days gives full protection on daily PrEP. Fewer than that, or any 2-1-1 gap, needs advice, and possibly PEP.
Do I need an HIV test after a PrEP missed dose?
Not for a single late pill. After a longer gap with condomless sex, a test before restarting is sensible; book an HIV test with us and we will advise on timing.
Written by the HIV PrEP Bangkok team, based on NHS and CDC guidance. Last updated 2 October 2026.