Most women know what emergency contraception, or the morning after pill, is. But relatively few know all the details.
When you need the morning after pill, you have to make decisions quickly. Which pill is right for you, how long you have and what to expect afterwards can all affect your choice, and the outcome. Here are five things worth knowing before you ever need them.
Whichever pill you take, the sooner you take it, the better it works.
1. There are two morning after pills, and they cover different time windows
The two morning after pills available in the UK are ellaOne (ulipristal acetate 30mg) and Levonelle (levonorgestrel 1.5mg). Both are emergency contraceptives, but each has its own features worth bearing in mind.
Levonelle works for up to 72 hours (three days) after unprotected sex, and it becomes less effective over that time.1 ellaOne works for up to 120 hours (five days), and is thought to stay effective more consistently across that whole window than levonorgestrel.2
Within 72 hours? Both are options for you. Between 72 and 120 hours, only ellaOne is suitable.
2. The sooner you take it, the better it works
Both morning after pills work mainly by delaying or preventing ovulation. Neither is a form of abortion. They work before fertilisation happens, and neither has any effect if you're already pregnant.1
Because timing is so central to how the pill works, acting quickly matters. The sooner you take emergency contraception, the more effective it usually is, and Levonelle in particular becomes less effective the longer you wait.1
Overall, research suggests around 1 to 2 in every 100 women who take an emergency contraceptive pill will get pregnant.3
ellaOne is thought to stay more effective across its five-day window, though taking it as soon as possible is still recommended.2
Both pills are available without a prescription from UK pharmacies. You can also order emergency contraception online through a registered UK pharmacy, without a GP appointment. Getting it quickly is the priority.
3. Your weight may affect which option suits you best
This is one of the least well-known things about the morning after pill. Evidence suggests levonorgestrel-based pills may work less well above a certain body weight or body mass index (BMI).
The College of Sexual and Reproductive Healthcare (formerly the FSRH) advises that effectiveness may be reduced if you weigh more than 70kg or have a BMI above 26.4
If that applies to you, it recommends either a higher dose of levonorgestrel, switching to ellaOne, or considering a copper intrauterine device (IUD).4 The copper IUD is the most effective form of emergency contraception, whatever your weight, and it can stay in as ongoing contraception.
Weigh over 70kg, or have a BMI above 26? Mention it in your consultation, as it can change which option is best for you.
Not sure which option is right for you? Ask the pharmacist before you buy. They can advise based on your circumstances.
4. Side effects are normal, and a late period doesn't mean it's failed
After taking the morning after pill, it's common to have nausea, a headache, dizziness, tiredness or irregular bleeding. These are well-recognised morning after pill side effects, and they usually pass without treatment.5
One specific point to keep in mind: emergency contraception can delay your next period by a few days, or sometimes by up to a week. That's a normal effect and doesn't mean the pill hasn't worked.5
However, if your period is more than seven days late, or noticeably lighter than usual, take a pregnancy test.
If you vomit within three hours of taking either pill, it may not have been absorbed properly. Contact a pharmacist or GP as soon as possible, as you may need to take another dose.
Severe pain low down on one side of your tummy in the weeks after taking it? Get urgent medical help, as it can be a sign of an ectopic pregnancy.
5. It's worth having emergency contraception at home before you need it
Both ellaOne and Levonelle have a shelf life of several years, so buying one in advance is a practical option, not an unusual one.2,4
Because effectiveness is so closely tied to how soon you take it, having a pill at home removes the most common cause of delay. That's finding an open pharmacy, waiting for same-day delivery or arranging a consultation under pressure.
You can order emergency contraception online through Pharmica after a short consultation, with no GP appointment, and have it delivered for next-day use. Preparing in advance means that if you ever need it, acting quickly is easy.
If you do keep a pill at home, check the expiry date every so often and replace it when needed. And as with any use of emergency contraception, if you find yourself relying on it regularly, speak to a pharmacist or GP about a longer-term method.
Frequently asked questions
How effective is the morning after pill?
Both pills are most effective when taken as early as possible. Levonelle is up to 95% effective within 24 hours of unprotected sex, falling to around 85% between 25 and 48 hours, and 58% between 49 and 72 hours.1 ellaOne is considered more effective later in its window and remains suitable for up to 120 hours.2 No morning after pill is 100% effective, and neither is a substitute for regular contraception.
How does the morning after pill work?
Both pills work primarily by delaying or preventing ovulation - the release of an egg - so that fertilisation cannot occur. They do not cause an abortion and have no effect if you are already pregnant.1 ellaOne (ulipristal acetate) works by blocking the action of progesterone to delay ovulation. Levonorgestrel works by mimicking a hormone that prevents the ovaries from releasing an egg.2
Can the morning after pill delay your period?
Yes. It is common for the morning after pill to shift your next period by a few days to a week, either earlier or later than expected.4 This is a normal hormonal effect and does not mean the pill has not worked. If your period is more than seven days late or significantly lighter than usual, take a pregnancy test.
Can I take the morning after pill more than once?
There is no medical reason you cannot take the morning after pill more than once, including within the same menstrual cycle. However, it is not designed to replace regular contraception and becomes less reliable with repeated use within a single cycle.1 If you are finding yourself using it frequently, speak to a pharmacist or GP about long-term contraceptive options.
References
- NHS. Levonelle and ellaOne (emergency contraception). Available at: nhs.uk
- Electronic Medicines Compendium (eMC). Zentiva Ulipristal 30mg, Summary of Product Characteristics. Available at: medicines.org.uk/emc
- NHS. How to take the emergency contraceptive pill (morning after pill). Available at: nhs.uk
- College of Sexual and Reproductive Healthcare (CoSRH). Emergency Contraception guideline. Available at: cosrh.org
- Electronic Medicines Compendium (eMC). Levonelle 1500 micrograms tablet, Summary of Product Characteristics. Available at: medicines.org.uk/emc
This article is intended for informational purposes only and does not replace professional medical advice. Always read the patient information leaflet supplied with your medication and speak to a healthcare professional if you have specific concerns.