The morning-after pill is emergency contraception used to lower the chance of pregnancy after unprotected sex or contraceptive failure. The most common types work mainly by delaying or preventing ovulation, so no egg is released to be fertilized. It works best the sooner it is taken — and it is a backup, not a regular method.
What to do now
If this is urgent, work through these steps in order.
- Act today, not tomorrow. Every type of emergency contraception works better the sooner it is used.
- Count the hours since the unprotected sex. Under 72 hours opens up all options; up to 120 hours still leaves ulipristal acetate and the copper IUD.
- Go to a pharmacy or sexual health clinic. In many countries emergency contraceptive pills are available directly from a pharmacist without an appointment.
- Tell them the timing, your usual contraception, any medicines you take, and your weight if asked — these determine which option is recommended for you.
- If it has been close to 5 days, ask specifically about a copper IUD, which stays effective latest in the window.
- Plan the follow-up: when to restart your regular method, and a pregnancy test if your period is late.
How it works
According to the NHS and WHO, the morning-after pill works primarily by stopping or delaying the release of an egg (ovulation). If ovulation hasn't happened, sperm can't fertilize an egg, and pregnancy is much less likely.
An important point that causes confusion: emergency contraceptive pills are not the same as abortion pills. They do not end an established pregnancy and will not work if you are already pregnant.
The two main types
Levonorgestrel (e.g. Plan B, Levonelle)
- Available widely, often without prescription.
- Most effective when taken within 72 hours (3 days) of unprotected sex.
- Effectiveness drops the longer you wait.
Ulipristal acetate (ellaOne)
- Can be taken up to 120 hours (5 days) after unprotected sex.
- Research suggests it stays effective later in this window than levonorgestrel.
The copper IUD
A copper IUD is the most effective form of emergency contraception of all — when fitted by a provider within 5 days, it prevents the large majority of expected pregnancies and can then stay in as ongoing contraception. ACOG notes this is the most effective emergency option. It requires an appointment with a trained clinician rather than a pharmacy visit, which is the main practical barrier — but if you want long-term contraception anyway, it solves both problems at once. Our guide to how the IUD works explains what fitting involves.
How soon to take it
The single most important factor is speed. Both pill types work better the sooner they're taken, because once ovulation has already occurred, they are less likely to help. If you're choosing between options or unsure, a pharmacist or healthcare provider can advise quickly.
How effective is it?
Emergency contraception meaningfully reduces the risk of pregnancy, but it is less reliable than regular contraception and does not guarantee prevention. Effectiveness depends on:
- Timing — sooner is better.
- Where you are in your cycle — it's less effective if ovulation has already happened.
- Body weight — some evidence suggests levonorgestrel may be less effective at higher body weights; a provider may recommend ulipristal or a copper IUD instead.
Because it isn't 100%, take a pregnancy test if your period is more than a week late or unusually light.
Who each option suits
Levonorgestrel is the most widely stocked option and the easiest to obtain quickly, which matters when speed is the priority. Ulipristal acetate is often preferred when more time has passed, or at higher body weights. The copper IUD suits people who are already within five days, can get a clinic appointment, and would welcome years of highly effective contraception afterwards.
Emergency contraception is not a good fit as a routine method — not because it is unsafe, but because it is far less reliable than regular contraception and involves repeated cost and inconvenience. If you have needed it more than once, that is a signal to review your ongoing method rather than a reason for embarrassment.
Cost and access — what to expect
In many countries emergency contraceptive pills are sold over the counter at pharmacies, and public health services, sexual health clinics, and some general practices supply them free of charge. In the UK, the NHS provides emergency contraception free from a range of services. Rules on age, prescription requirements, and price differ substantially between countries, so we don't quote figures.
At the pharmacy, expect a short, routine, confidential conversation — often at a counter or in a private consultation area. The pharmacist will ask when the unprotected sex happened, what contraception you normally use, whether you take any other medicines, and about your medical history. These questions are there to choose the right option, not to judge you; pharmacists supply emergency contraception constantly and treat it as ordinary care.
After taking it
- Your next period may come earlier or later than usual, and may be heavier or lighter.
- Mild side effects such as nausea, headache, tiredness, or abdominal discomfort can occur and pass quickly.
- If you vomit within 2 hours of levonorgestrel or 3 hours of ulipristal acetate, the NHS advises the dose may not have been absorbed — seek advice about taking another.
- Ask when to restart your regular method. The NHS notes ulipristal acetate can interact with hormonal contraception, so there is a waiting period before starting or restarting a hormonal method, with condoms used in the meantime.
- Emergency contraception does not protect you for the rest of the cycle. Use condoms or another method for any further sex until your regular contraception is reliably in effect — see how long the pill takes to work.
- If you took it because of missed pills, our guide to what to do after a missed pill covers what to do next with the rest of your pack.
- If you're regularly relying on it, it's worth talking to a provider about an ongoing method — see our guide to birth control methods compared.
The bottom line
The morning-after pill is a safe, effective backup that works mainly by delaying ovulation — and the sooner you take it, the better it works. It isn't a substitute for regular contraception or STI protection, and it doesn't cover the rest of your cycle. If you frequently need it, a healthcare provider can help you find a reliable ongoing method; our contraception guide is a good place to start comparing. This article is general education and is not a substitute for individualized medical advice.
