How does the morning after pill work?
The morning after pill stops you from getting pregnant if you’ve had unprotected sex. You may need to take it after a condom breaks or if you’ve forgotten to take your contraceptive pill.
There are 2 types of morning after pills, also known as emergency contraception, and they work in different ways. You can choose between levonorgestrel or the branded version, Levonelle and EllaOne. To help you decide which one is right for you, read about how they work and their potential side effects.
There’s also a helpful FAQs section at the end that answers some of the most common questions about the morning after pill.
How does the morning after pill work?
The morning after pill works by delaying or stopping ovulation (when your ovaries release an egg).
Hormones regulate your menstrual cycle, and one of them is called the luteinising hormone (LH). When the level of LH rises, your ovaries release an egg that’s ready for sperm to fertilise.
The active ingredients in Levonelle, unbranded levonorgestrel and EllaOne (ulipristal acetate) lower the levels of LH in your body. This stops ovulation from occurring and reduces your chance of becoming pregnant.
How effective is the morning after pill?
Morning after pills are highly effective. Levonelle and the unbranded levonorgestrel are around 97 to 99% effective, whereas EllaOne has a 99% effective rate at preventing pregnancy.
Levonelle, unbranded levonorgestrel and EllaOne can only work if you take the pill before ovulation. EllaOne can be effective a little longer than Levonelle. If you have unprotected sex after ovulation, speak to your doctor for more advice.
A morning after pill is most effective if you take it in the first 12 to 24 hours after unprotected sex. You only need to take 1 morning after pill to effectively prevent a pregnancy. If you have a high body mass index (BMI) then you might need to take more than 1 pill for it to be effective. Contact your doctor or pharmacist to find out the right contraceptive option for you.
The most effective form of emergency contraception is the Copper IUD (the copper coil). This is a small device that is fitted into the womb and can be fitted up to 5 days after unprotected sex. It is more than 99% effective and can also be used as a regular contraception long term. This can be fitted at a sexual health clinic or by some GPs.
How soon after unprotected sex do you need to take the morning after pill?
You should take the morning after pill as soon as you know you’ve had unprotected sex. The sooner you take it, the higher your chance is of preventing pregnancy.
Levonelle and unbranded levonorgestrel are effective for up to 3 days (72 hours) after unprotected sex, and EllaOne is effective for up to 5 days (120 hours).
How do you know if the morning after pill worked?
You’ll know if the morning after pill has worked once your next period has arrived. This might take a little patience and if there’s anything unusual about your period, let your doctor know. It’s best to take a pregnancy test 3 weeks after using the morning after pill to confirm that you are not pregnant.
As you wait for your period, keep an eye on how your body feels over the next few weeks. If you feel any symptoms of pregnancy, such as feeling sick or tiredness that isn’t normal for you, take a pregnancy test.
Which morning after pill is best for me?
Which morning after pill is best for you depends on when you last had unprotected sex.
If you’ve had unprotected sex within the last 72 hours (3 days), you can take Levonelle, unbranded levonorgestrel or EllaOne.
If it’s between 72 to 120 hours after unprotected sex (between 3 to 5 days), you can still take EllaOne for emergency contraception.
EllaOne can interact with other hormonal contraception. So if you are already using contraception, you need to wait at least 5 days before using your contraception again. Levonorgestrel and unbranded levonorgestrel do not interact with other contraception, so you can continue to use your contraception as usual after taking this.
If you’re taking the following medicines, Levonelle, unbranded levonorgestrel and EllaOne may be less effective for you:
- epilepsy treatment such as carbamazepine, phenytoin, phenobarbital or primidone
- tuberculosis treatment such as rifampicin or rifabutin
- products containing St John’s wort, a herbal remedy for low moods
- ritonavir or efavirenz, to treat HIV
- antifungal medicine, such as griseofulvin
Levonelle and unbranded levonorgestrel can also affect how ciclosporin (an immunosuppressant) works.
If you’re taking any of the above medicines, EllaOne might not be suitable for you. Levonelle and unbranded levonorgestrel can still work if you take it with some of these medicines. But you may need to take more than 1 pill.
Speak to your doctor or pharmacist for further advice on emergency contraception if you’re taking any of these medicines.
Are there any side effects to taking the morning after pill?
There are some side effects you may experience after taking the morning after pill. Levonelle, unbranded levonorgestrel and EllaOne can cause similar side effects. These side effects only last for a short time and should clear up after a few days.
Some common short term side effects of the morning after pill are:
- feeling sick or vomiting
- stomach pain
- mood swings
- feeling tired
Uncommon side effects of the morning after pill include:
- changes in your sex drive
- having an earlier or later period
- spotting in between your period
Taking the morning after pill can affect when you get your period. Your menstrual cycle should go back to normal after a month or two after using the morning after pill.
There are no known long term side effects of Levonelle, unbranded levonorgestrel or EllaOne.
However, you should not use the morning after pill as a form of contraception. You should only take the morning after pill in an emergency situation to prevent pregnancy. Speak to your doctor for advice on contraception for more information.
Morning after pill FAQs
Can the morning after pill affect fertility?
Taking the morning after pill does not affect your fertility, so you can still get pregnant in future if you want to try for a baby.
If you have unprotected sex after you take the morning after pill, you will not be protected and can still get pregnant.
Does the morning after pill work during ovulation?
The morning after pill does not work during ovulation. Levonelle, unbranded levonorgestrel, and EllaOne have been designed to work to prevent ovulation. If you have already started ovulating, neither of these morning after pills will work. The Copper IUD may still be an option if you have ovulated, so you should speak to a doctor if you think you have ovulated.
Your menstrual cycle is more than just your period. Get to know your body and how you feel throughout your monthly cycle to know what’s normal for you.
How often can you take the morning after pill?
You can take the morning after pill more than once in your menstrual cycle. But you should not use the morning after pill as regular contraception, as there are more effective methods.
You should not use EllaOne in the same menstrual cycle as Levonelle or unbranded levonorgestrel. If you cannot take EllaOne, Levonelle or levonorgestrel, you may need to have a copper coil fitted in your womb to prevent pregnancy. The copper coil is also known as an intrauterine device or IUD, and is hormone free.
What if you vomit after taking the morning after pill?
If you vomit after taking the morning after pill, you may need to take another pill as you will not absorb enough medicine to prevent a pregnancy.
So if you vomit within 3 hours of taking EllaOne or 2 hours of taking Levonelle or levonorgestrel, speak to a GP, pharmacist or sexual health clinic as soon as possible. They may give you another dose of the morning after pill or advise that you need to have an IUD (intrauterine device) fitted.
Dr Kathryn Basford
Dr Kathryn Basford is a qualified GP who works as a GP in London, as well as with ZAVA. She graduated from the University of Manchester and completed her GP training through Whipps Cross Hospital in London.Meet our doctors
Article created: 28 Oct 2021
Last reviewed: 28 Oct 2021
Levonelle 1500mcg tablet (PIL) [Jan 2020] [accessed October 2021]
ellaOne 30mg tablet (PIL) [Jan 2021] [accessed October 2021]
How effective is emergency contraception? (NHS) [Aug 2019] [accessed October 2021]
Emergency contraception (NHS) [Feb 2019] [accessed October 2021]
ellaOne® Questions [Feb 2020] [accessed October 2021]
You might need emergency contraception if you’ve recently had unprotected sex and want to reduce your risk of getting pregnant. Asda Online Doctor by ZAVA offers a morning after pill service, which includes a variety of options.
(Reviews are for ZAVA UK)