The emergency contraceptive pill, also known as the morning-after pill or post-coital pill, can be used by a woman to prevent 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.

The emergency contraceptive pill can be used up to five days (120 hours) after having unprotected sex. However, the sooner it is taken, the more likely it is to prevent pregnancy.

It can be taken more than once during your menstrual cycle, but 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.

How effective is it?

The effectiveness of the emergency contraceptive pill depends on how soon you take it after sex. Taking it within 12 hours of having sex gives the best chance of preventing a pregnancy.

The emergency contraceptive pill is:

• 95% effective if taken within 24 hours of having sex
• 85% effective if taken within 24-48 hours of having sex
• 58% effective if taken within 48-72 hours of having sex

How the emergency contraceptive pill works

The emergency contraceptive pill prevents the ovaries releasing an egg (ovulation). It also:

• thickens the mucus in the neck of the womb, so it is harder for sperm to penetrate into the womb and reach an egg
• thins the lining of the womb, so there is less chance of a fertilised egg implanting into the womb and being able to grow

Types of emergency contraceptive pill

There are currently two brands of emergency contraceptive pill available in the UK:

• Levonelle is the most commonly used emergency contraceptive pill. It can be taken up to three days (72 hours) after unprotected sex and is available free of charge on prescription or can be bought from your local pharmacy if you are over 16 years of age.
• ellaOne is a newer type of emergency contraceptive pill that can be taken up to five days (120 hours) after having unprotected sex. It is only available on prescription and only recommended in women over the age of 18.

Other emergency contraception

The copper intrauterine device (IUD) is another method of emergency contraception. This prevents pregnancy if it is fitted within five days of having unprotected sex. Read more about the intrauterine device.

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

However, the emergency contraceptive pill may interact with some medicines (see below).

Breastfeeding women

The emergency contraceptive pill can be taken when 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.

Pregnancy

There is no evidence that the emergency contraceptive pill harms a developing baby. If you are pregnant when you take the emergency contraceptive pill, or you become pregnant after taking it, you might have a slightly increased risk of developing an ectopic pregnancy. You can discuss this further with your GP.

When to avoid it

The emergency contraceptive pill can interact with medicines used to treat epilepsy, HIV and tuberculosis, and with the complementary medicine St John’s Wort. These types of drugs are called enzyme inducers.

The dose of Levonelle or ellaOne may need to be increased if you are using this medication, or you may be advised to use the emergency intrauterine device (IUD) instead.

It is always best to check with your doctor whether any of your medication may interact and change the effectiveness of 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
• 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 (being sick) - seek medical advice if you vomit within three hours of taking the emergency contraceptive pill

Any side effects will normally pass quickly.

When to see a doctor or nurse

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 may also want to 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 (tummy)

It is fine to take the emergency contraceptive pill if you are already taking a combined oral contraceptive pill or progestogen-only pill.

If you needed to take the emergency contraceptive pill because you forgot to take some of your regular contraceptive pills or did not use your patch or vaginal ring correctly, you should take your next contraceptive pill, insert a new ring or apply a new patch within 12 hours of taking the emergency contraceptive pill.

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

You will need to use additional contraception, such as condoms, for:

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

Interactions with other medicines

The emergency contraceptive pill may interact with some other medicines. This includes some immunosuppressant drugs (medicine that weakens the immune systrem), such as ciclosporin, and medicines used to treat liver disease.

There should be no interaction between the emergency contraceptive pill and most antibiotics.

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.

The emergency contraceptive pill prevents a fertilised egg from implanting in your womb. However, if you become pregnant despite taking the emergency contraceptive pill, there is a slightly higher risk of it being an ectopic pregnancy.

An ectopic pregnancy occurs when the fertilised egg implants outside of the womb, usually in the fallopian tube.

If you become pregnant after taking the emergency contraceptive pill, it is important that you see your GP to rule out the possibility of an ectopic pregnancy. This is particularly important if you have previously had:

• an ectopic pregnancy
• fallopian tube surgery
• pelvic inflammatory disease

You should always see your GP if you develop severe abdominal (tummy) pain. Read more about ectopic pregnancy.