• Confidential assessment
  • Reviewed by our doctors
  • Same-day collection
On this page

How effective is the morning after pill?

How effective is the morning after pill?

Many people question ‘how effective is the morning after pill?’, but the answer largely depends on one thing: how soon after unprotected sex the pill is taken. Beyond this, there can be some differences depending on the type you use. This article examines the two most widely used morning after pills – Levonorgestrel (Prevenelle or Norlevo) and ellaOne – as well as the emergency coil, or IUD.

What is ellaOne?

ellaOne is the most effective morning after pill (although the emergency coil is the most effective form of emergency contraception). It contains ulipristal acetate, a chemical that prevents pregnancy.

How does ellaOne work?

Ulipristal acetate is the active ingredient in ellaOne. This ingredient is a chemical that prevents or delays your ovaries from releasing an egg (ovulating), therefore decreasing the chances of sperm coming into ontact with an egg and fertilising it.

ellaOne effectiveness

ellaOne should be taken as soon as possible after unprotected sex to maximise its effectiveness. However, ellaOne has a longer window of use than Levonorgestrel. ellaOne has to be taken within five days (120 hours) of unprotected sex – allowing 48 hours extra than Levonorgestrel.

ellaOne is taken as a single tablet. It's most effective when taken as soon as possible, and reduces the risk of pregnancy to 9 in 1000 when taken within 24 hours. 

Things to consider

Potential side effects are very rare. The most likely are irregular bleeding, headache, nausea and stomach pain, but these side-effects are rarely severe. Don’t take ellaOne if you believe you are already pregnant and bear in mind that ellaOne may interact with certain medicines. Consult the medical instructions within the packet or speak with your GP if you have major concerns.

If you vomit within three hours of taking ellaOne you must take another tablet as soon as possible. Recurrent vomiting probably means your body is rejecting the treatment. You could try Levonorgestrel provided you are within 72 hours of sexual intercourse, although Levonorgestrel’s decreasing effectiveness means the IUD is probably the better option. 

What is Levonorgestrel?

Levonorgestrel is the most commonly used morning after pill, although it is sometimes called its branded name Prevenelle or Norlevo. Although less effective than ellaOne, it has been around longer and costs less. Levonorgestrel is a synthetic hormone that prevents pregnancy.

How does Levonorgestrel work?

The active ingredient in Levonorgestrel or Prevenelle or Norlevo is levonorgestrel. This a synthetic hormone which works to prevent pregnancy by stopping the ovaries from releasing an egg and also stopping sperm fertilising an egg if it had already been released.

Levonorgestrel effectiveness

Levonorgestrel is most effective when taken within 12 hours of unprotected sex, although it can be effective for up to 72 hours after sex. You should bear in mind, however, that this effectiveness decreases over time. Taken in the first 12 hours it's thought to be 99% effective, but this will reduce on the second and third day. 

For this reason, taking Levonorgestrel three days after unprotected sex may not leave you as well-protected as you hoped.

Things to consider

Levonorgestrel comes as a tablet, taken once only. However, you can take Levonorgestrel again during the same menstrual cycle if you require emergency contraception on another occasion. Levonorgestrel should not disrupt any contraception such as the combined pill. 

In contrast, ellaOne is not recommended to be used more than once in a menstrual cycle. You should never take Levonorgestrel and ellaOne within the same menstrual cycle. 

Most women experience no side effects after taking Levonorgestrel. Should side effects occur, the most common are irregular bleeding, headache, nausea and stomach pain. Certain medical conditions make Levonorgestrel unsafe to take. If you order through our site, one of our doctors will check that you are eligible beforehand.

If you're sick within three hours taking Levonorgestrel, you will need to take another tablet as soon as possible. If vomiting recurs then your body has probably rejected the treatment. You should seek another form of emergency contraception – mostly likely the IUD coil (see below). 

The emergency IUD, or coil

The IUD is the most effective form of emergency contraception. It’s is a small T-shaped device made from plastic and copper that is inserted into the uterus to prevent pregnancy. The coil stops the egg and sperm from surviving in the womb or fallopian tubes. It is commonly used as a form of long-term contraception. However the coil is also a very effective emergency contraception – indeed more so than either Levonorgestrel or ellaOne. You can get the coil fitted within five days of unprotected sex and it will be 99.9% effective.

To have the coil fitted you must visit your GP or local sexual health clinic. There you will have an internal examination to discover the size and position of your womb. The insertion process takes between 15 to 20 minutes. The coil can be an effective form of contraception for up to 10 years, depending on the version used.

However, if you want to remove the coil the procedure can be done at any time by a trained doctor or nurse. Once the coil is removed your fertility will return to normal.

Some women find the coil causes vaginal bleeding and pain. Most, however, experience no discomfort. Periods can be heavier although this tends to clear after a few months. The coil doesn’t prevent sexually transmitted infections so you will still need to use a condom during sex if you aren’t certain that your partner is STI-free.

The coil should not be fitted if you have:

  • An untreated pelvic infection or STI
  • Unexplained vaginal bleeding
  • Certain abnormalities of the cervix or womb

The doctor or nurse fitting the coil will examine you beforehand to ensure the coil is appropriate for you. For more information, visit your GP or local sexual health clinic.

Does emergency contraception protect against STIs?

No, not at all. If you have had unprotected sex and are worried that you might have an STI then you should visit your local sexual health clinic for testing. 

You should also remember that the morning after pill isn’t a suitable alternative to regular contraception. It is designed for one-off use. If you do not want to use long-term hormonal contraception, barrier methods such as condoms could be the answer. They are far cheaper than using emergency contraception regularly, and offer effective protection against sexually transmitted infections.

Can you get pregnant after taking the morning after pill?

ellaOne and Levonorgestrel are most effective at preventing pregnancy the sooner they are taken after unprotected sex. A 2017 review by the NHS in the UK estimated that 98-99% of women who take ellaOne after unprotected sex will not become pregnant. It is estimated that 97.4-99.4% of women will not become pregnant after taking Levonorgestrel.

How effective is the morning after pill when ovulating?

Both types of morning after pill, Levonorgestrel and ellaOne are effective only if taken before the release of an egg from the ovary (ovulation). However, when compared with Levonorgestrel, ellaOne has been shown to continue being effective later in the menstrual cycle.

How long does the morning after pill stay effective?

The morning after pill is only effective after unprotected sex. If you have unprotected sex at any time after taking Levonorgestrel or ellaOne, you can become pregnant.

Neither form of morning after pill is intended to be used as a regular form of contraception. But you can use emergency contraception more than once in a menstrual cycle if you need to.

How do I know that the morning after pill has worked? When should I take a pregnancy test?

If your period is more than seven days late; if it is unusually light or unusually heavy; or if you experience symptoms such as abdominal (stomach) pain, breast tenderness, vomiting or nausea, you may be pregnant.

Can you take the morning after pill twice in a week?

You can take the morning after pill more than once in a menstrual cycle, if you need to. However it is worth bearing in mind that the morning after pill shouldn’t be used as a regular form of contraception.

Looking for the morning after pill?

Go to our service



Authors and editors

Reviewed and updated by: Our clinical team Date reviewed: 23-08-2023