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Emergency contraceptive pill
Emergency contraceptive pill

The emergency contraceptive pill, also known as the morning-after pill or post-coital pill, can be used by a woman to reduce the risk of pregnancy after having unprotected sex.

It can also be used if another method of contraception has failed, for example if a condom splits or you have forgotten to take one of your contraceptive pills.

It does not protect you against pregnancy during the rest of your menstrual cycle and is not intended to be a regular form of contraception. Using the emergency contraceptive pill repeatedly can severely disrupt your natural menstrual cycle.

The emergency contraceptive pill does not protect against sexually transmitted infections.

Types of emergency contraceptive pill

There are two kinds of emergency contraceptive pill. Levonelle has to be taken within 72 hours (three days) of sex, and ellaOne has to be taken within 120 hours (five days) of sex. Both pills work by preventing or delaying ovulation (release of an egg).

How the emergency pill works


Levonelle contains levonorgestrel, a synthetic version of the natural hormone progesterone. In a woman’s body, progesterone plays a role in ovulation and preparing the uterus for accepting a fertilised egg.

It’s not known exactly how Levonelle works, but it’s thought to work primarily by preventing or delaying ovulation. You can take Levonelle more than once in a menstrual cycle. It does not interfere with your regular method of contraception.


ellaOne contains ulipristal acetate, which means it stops progesterone working normally. It prevents pregnancy mainly by preventing or delaying ovulation. ellaOne may prevent other types of hormonal contraception from working for a week after use, and it’s not recommended for use more than once in a menstrual cycle.

ellaOne used to be available only on prescription, but it's now available to buy in some pharmacies.

Levonelle and ellaOne do not protect you against pregnancy during the rest of your menstrual cycle and are not intended to be a regular form of contraception. Using the emergency contraceptive pill repeatedly can disrupt your natural menstrual cycle.

How effective is the emergency pill at preventing pregnancy?

It can be difficult to know how many pregnancies the emergency pill prevents, because there is no way to know for sure how many women would have got pregnant if they didn't take it.

A trial undertaken by the World Health Organization (WHO) indicated that levonorgestrel (the drug in Levonelle) prevented:

  • 95% of expected pregnancies when taken within 24 hours of sex
  • 85% if taken within 25–48 hours
  • 58% if taken within 49–72 hours

More recent studies suggest that the prevention rate might be lower, but still substantial.

A study published in 2010 showed that of 1,696 women who received the emergency pill within 72 hours of sex, 37 became pregnant (1,659 did not). Of 203 women who took the emergency pill between 72 and 120 hours after unprotected sex, there were three pregnancies.

How it affects your period

After taking the emergency contraceptive pill, most women will have a normal period at the expected time. However, you may have your period later or earlier than normal.

If your period is more than seven days late, or is unusually light or short, contact your GP as soon as possible to check for pregnancy.

Who can use the emergency pill?

Most women can use the emergency contraceptive pill. This includes women who cannot usually use hormonal contraception, such as the combined pill and contraceptive patch.


The World Health Organization does not identify any medical condition that would mean a woman shouldn’t use Levonelle.


The Faculty of Sexual and Reproductive Healthcare (FSRH) advises that ellaOne should not be used by women who:

  • may already be pregnant
  • are allergic to any of the components of the drug
  • have severe asthma that is not properly controlled by steroids
  • have hereditary problems with lactose metabolism

ellaOne will not be effective in women who are taking liver enzyme inducing medication.

Pregnancy and breastfeeding


There is no evidence that Levonelle harms a developing baby. It can be used even if there has been an earlier episode of unprotected sex in the menstrual cycle in addition to the current episode. Levonelle can be taken while breastfeeding. Although small amounts of the hormones contained in the pill may pass into your breast milk, it is not thought to be harmful to your baby.


There is limited information on the safety of ellaOne in pregnancy. The FSRH does not support the use of ellaOne if a woman might already be pregnant. The safety of ellaOne during breastfeeding is not yet known, so the manufacturer recommends that you do not breastfeed for up to 36 hours after taking this pill.

If you are already using the pill, patch, vaginal ring or contraceptive injection

If you need to take the emergency pill because you:

then you should:

  • take your next contraceptive pill, apply a new patch or insert a new ring within 12 hours of taking the emergency pill

You should then continue taking your regular contraceptive pill as normal.

If you have taken Levonelle, you will need to use additional contraception, such as condoms, for:

  • the next seven days if you use the patch, ring, combined pill or injection
  • the next two days if you use the progestogen-only pill

If you have taken ellaOne, you will need to use additional contraception, such as condoms, for:

  • the next 14 days if you use the patch, ring, combined pill or injection
  • the next nine days if you use the progestogen-only pill

What are the side effects of using the emergency pill?

Taking the emergency contraceptive pill has not been shown to cause any serious or long-term health problems. However, it can sometimes have side effects. Common side effects include:

  • abdominal (tummy) pain
  • headache
  • irregular menstrual bleeding (spotting or heavy bleeding) before your next period is due
  • nausea (feeling sick)
  • tiredness

Less common side effects include:

  • breast tenderness
  • dizziness
  • headache
  • vomiting (seek medical advice if you vomit within two hours of taking Levonelle, or three hours of taking ellaOne, as you will need to take another dose or have an IUD fitted)

If you are concerned about any symptoms after taking the emergency contraceptive pill, contact your GP or speak to a nurse at a sexual health clinic. You should talk to a doctor or nurse if:

  • you think you might be pregnant
  • your next period is more than seven days late
  • your period is shorter or lighter than usual
  • you have any sudden or unusual pain in your lower abdomen (this could be a sign of an ectopic pregnancy, where a fertilised egg implants outside the womb – this is rare but serious and needs immediate medical attention)

The emergency pill and other medicines

The emergency contraceptive pill may interact with other medicines. These include:

  • the herbal medicine St John’s Wort
  • some medicines used to treat epilepsy
  • some medicines used to treat HIV
  • some medicines used to treat tuberculosis (TB)
  • medication such as omeprazole (an antacid) to make your stomach less acidic

ellaOne cannot be used if you are already taking one of these medicines as it may not be effective.

Levonelle may still be used, but the dose may need to be increased – your doctor or pharmacists will be able to advise on this.

There should be no interaction between the emergency pill and most antibiotics. Two enzyme-inducing antibiotics (called rifampicin and rifabutin), used to treat or prevent meningitis or TB, may affect ellaOne while they’re being taken and for 28 days afterwards.

If you want to check that your medicines are safe to take with the emergency contraceptive pill, ask your GP or a pharmacist. You should also read the patient information leaflet that comes with your medicines.

Can I get the emergency contraceptive pill in advance?

You may be able to get the emergency contraceptive pill in advance of having unprotected sex if:

  • you are worried about your contraceptive method failing
  • you are going on holiday
  • you cannot get hold of emergency contraception easily

Ask your GP or nurse for further information on getting advance emergency contraception.

You can get contraception at:

  • most GP surgeries
  • community contraception clinics
  • some GUM clinics
  • sexual health clinics
  • some young people's services

Find a clinic near you

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Selected links

NHS Direct Wales links:

Intrauterine device(IUD)

Emergency contraception 

Find Services: emergency contraceptive pill

External Links:

FPA: emergency contraception guide

Contraception – the contraceptive pill - Including guidance issued in 2011 on taking taking antibiotics when on the pill.

Brook: emergency contraception

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The information on this page has been adapted by NHS Wales from original content supplied by NHS Choices.
Last Updated: 02/10/2014 10:46:21