Morning-after pill: how late is too late?
Levonelle can work up to 72 hours after unprotected sex and ellaOne up to 120, but both work best taken early. What the time limits really mean.
The short answer: it depends which pill. Levonorgestrel (Levonelle and generics) is licensed up to 72 hours — three days — after unprotected sex, while ulipristal acetate (ellaOne) works up to 120 hours, or five days. But "still allowed" is not the same as "works just as well": both pills are at their most effective in the first 24 hours, and every day of delay lowers the odds. If you are past three days, ellaOne or a copper coil are your remaining options — and the coil is the most effective choice at any point within its five-day window.
What are the two morning-after pills?
Levonorgestrel is a synthetic progestogen taken as a single 1.5 mg tablet. Ulipristal acetate (ellaOne) is a 30 mg tablet that modulates progesterone receptors. Both work primarily the same way: by delaying ovulation so that sperm waiting in the reproductive tract never meet an egg. Neither ends an existing pregnancy, and neither harms one that has already implanted — emergency contraception is contraception, not abortion.
How do the time windows actually work?
Sperm can survive for up to five days after sex. The pills work by holding back ovulation until any sperm have died off, which has two practical consequences. First, sooner really is better: taken within 24 hours, levonorgestrel prevents the large majority of expected pregnancies, but its effectiveness falls noticeably by day three. Ulipristal stays effective for longer and, unlike levonorgestrel, can still delay ovulation even when the fertile window has almost arrived — one reason it is the preferred pill later in the window or when ovulation is close. Second, timing in your cycle matters as much as time since sex: if ovulation has already happened, neither pill can work, which is why no pill is ever a guarantee.
Which pill should you take?
| Levonorgestrel (Levonelle) | Ulipristal acetate (ellaOne) | |
|---|---|---|
| Window after sex | Up to 72 hours | Up to 120 hours |
| Best taken | As soon as possible | As soon as possible |
| Works close to ovulation | Less reliable | More reliable |
| Higher body weight | May be less effective over 70 kg | Preferred, discuss if over 85 kg |
| Restarting the pill after | Straight away | Wait 5 days |
If you weigh more than 70 kg or have a BMI over 26, levonorgestrel may be less effective; a clinician may recommend ellaOne or a double dose of levonorgestrel instead. Some epilepsy, HIV and herbal medicines (notably St John's Wort) interfere with both pills — mention everything you take.
What if you vomit after taking it?
If you are sick within three hours of taking either pill, it may not have absorbed — contact a pharmacist or clinician, because you are likely to need another dose or a different option.
The copper coil: the most effective option of all
The copper IUD prevents over 99% of pregnancies when fitted within five days of unprotected sex (or within five days of your earliest likely ovulation). It works even if ovulation has already occurred, and it then provides ongoing contraception for years if you keep it. If your situation is high-stakes — mid-cycle timing, higher body weight, or a previous pill failure — ask an NHS sexual health clinic or your GP about an emergency coil fitting, ideally the same day. Taking a pill first while you arrange a fitting is a sensible belt-and-braces approach.
What happens afterwards?
Your next period may arrive early, on time or up to a week late, and one irregular cycle is common. Take a pregnancy test if your period is more than seven days late, lighter than usual, or if you have any pregnancy symptoms. Crucially, the morning-after pill does not protect the rest of your cycle: if you use ongoing contraception, restart it promptly — immediately after levonorgestrel, but five days after ellaOne, because the two medicines interfere — and use condoms in the meantime.
Frequently asked questions
Can I take the morning-after pill twice in one cycle?
Yes, if you need it again — but repeated use is a signal that a regular method would protect you far better. A clinician can help you choose one.
Does it cause an abortion?
No. Both pills act before pregnancy begins, mainly by delaying ovulation. They do not end an implanted pregnancy.
Will it affect my future fertility?
No. Emergency contraception has no effect on long-term fertility, however many times you use it.
Can I get it in advance, just in case?
Yes — having a pill at home before a trip or a period of unreliable contraception is legitimate and sensible, and it means you can take it at the most effective moment if you ever need it.
How do I know if it has worked?
There is no immediate test; the sign is your next period arriving. Test if it is more than seven days late — and if you took ellaOne and become pregnant despite it, tell a clinician promptly.
Emergency contraception is time-critical, so act first and reflect later. You can check your eligibility for the morning-after pill online now — a UK clinician reviews every request, and if the window is tight they can point you to the fastest local option, including an emergency coil.
Related reading
This guide is for general information and is not a substitute for personalised medical advice. If you are unsure what to do, speak to a pharmacist, your GP or an NHS sexual health clinic today, or call 111.
More clinically reviewed articles: all health guides.