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How Effective Is the Morning After Pill?
The morning after pill is considered most effective when taken at the correct time after unprotected sex. How effective the morning after pill is for you will depend on which one you’re taking and when you’re taking it.
By understanding how effective the morning after pill is, knowing which pill is right for you and when to take it is one of the most effective ways to prevent pregnancy after unprotected sex.
Contents
- How effective is the morning after pill?
- How does the morning after pill work?
- What can make the morning after pill less effective?
- Can I still get pregnant after taking the morning after pill?
- How effective is the morning after pill when ovulating?
- Can I have unprotected sex after using the morning after pill?
- Can I take the morning after pill more than once in a week?
How effective is the morning after pill?
The type of morning after pill you take and when you take it will change how effective it is. Some morning after pills are more effective when taken within 24 hours of unprotected sex but less effective when taken within 25-72 hours. Others can still be taken up to 5 days after unprotected sex, while still being effective.
Levonelle (the branded version of levonorgestrel) is effective for up to 72 hours after unprotected sex, whereas ellaOne is effective for up to 120 hours after unprotected sex. However, Levonelle is considered most effective when taken within 24 hours of unprotected sex.
The IUD (coil) is the most effective kind of emergency contraception. Trials indicate the failure rate for the IUD as emergency contraception is lower than 0.1%. This means that less than 1 in every 1,000 women who use the IUD as emergency contraception will fall pregnant.
How effective is Levonelle?
Manufacturer’s studies have shown levonelle to be:
- 95% effective if you take it within 1 day (24 hours) of unprotected sex. Levonelle begins to fall in effectiveness over time.
- 85% effective if you take it within 2 days (25-48 hours).
- 58% effective after 3 days (49-72 hours).
While Levonelle can be taken within 3 days (72 hours) of having unprotected sex, it is most effective if you take it within 24 hours of having unprotected sex.
How effective is ellaOne?
EllaOne is up to 98-99% effective and can be taken up to 5 days (120 hours) after having unprotected sex. However, because of how ellaOne works, the sooner you take it, the more effective it will be. This is because it, and Levonelle, must be taken before the release of an egg from your ovary. If you think you may have already ovulated you should speak to your doctor about having an emergency IUD fitted. This can be fitted up to 5 days after your earliest possible ovulation date.
The effectiveness of both ellaOne and Levonelle can be reduced if you have a high body mass index (BMI).
How effective are IUDs as emergency contraception?
IUDs are more than 99.9% effective and can stay in place for between 5 and 10 years, making them the most effective type of emergency contraceptive.
This means that fewer than 1 in 1000 women using an IUD will get pregnant
How does the morning after pill work?
The morning after pill delays the release of an egg from an ovary, stopping you from becoming pregnant. . You will normally only need to take 1 pill to get this effect. If you haven’t yet ovulated then the sooner you take the morning after pill after unprotected sex, the higher your chances are of avoiding pregnancy as there’s less chance of an egg being released.
The morning after pill is not an abortion pill. The morning after pill works by preventing a pregnancy from happening, not terminating a fertilised egg.
How does Levonelle work?
Levonelle contains levonorgestrel, a synthetic (man-made) version of the natural hormone progesterone produced by the ovaries. Taking it before ovulation stops or delays the release of an egg (ovulation). Levonelle has to be taken within 72 hours (3 days) of sex to prevent pregnancy. If you think you might be close to ovulating then EllaOne is likely to be more effective. Different studies show that Levonelle roughly 84% of expected pregnancies, depending on when it is taken within the 72 hour timeframe.
How does ellaOne work?
EllaOne contains ulipristal acetate, which stops progesterone working normally. If taken before ovulation this also works by stopping or delaying the release of an egg. EllaOne has to be taken within 120 hours (5 days) of sex to prevent pregnancy and is more effective than Levonelle, but not as effective as a copper coil.
What can make the morning after pill less effective?
The main things that can make the morning after pill less are:
BMI
Both types of morning after pill are less effective when you have a higher BMI. If your BMI is between 26-30 or your weight is between 70-85kg then EllaOne will be the more effective morning after pill for you. If your weight is over 85kg or your BMI is over 30 then an IUD is recommended instead of a morning after pill.
Vomiting (being sick) If you vomit shortly after taking the morning after pill, you must visit your GP or pharmacist straight away. You may need to take another dose or have an IUD fitted.
Medications
You should tell your doctor or pharmacist if you are currently taking, have recently taken, or plan to take any other medicines while using the morning after pill. Some medicines may prevent Levonelle or ellaOne from working effectively. These include:
- barbiturates and other medicines used to treat epilepsy (like phenytoin, primidone, or carbamazepine)
- treatment for HIV (like efavirenz or ritonavir)
- medicines used to treat tuberculosis (like rifabutin or rifampicin)
- medicine used to treat fungal infections (like griseofulvin)
- medicine to make your stomach less acidic (like omeprazole)
You should not take ellaOne together with another emergency contraceptive pill, especially if it contains levonorgestrel. Taking both together could make ellaOne less effective. EllaOne can also be less effective if you’ve taken hormonal contraception, period delay medication or HRT before taking ellaOne or if you use period delay medication or HRT after using ellaOne.
Can I still get pregnant after taking the morning after pill?
While both morning after pills are highly effective at preventing pregnancy, no emergency contraception is ever 100% effective. This means you can still get pregnant after taking the morning after pill, but it is unlikely if you take this in time and have not ovulated.
How do I know if the morning after pill has worked?
You’ll know the morning after pill has worked when you start your next period.. It is normal for your period to be a little earlier or later than usual. You can also find out if the morning after pill has worked by taking a pregnancy test 3 weeks after you have taken the pill.
How effective is the morning after pill when ovulating?
The morning after pill is not effective if you have started ovulating. The morning after pill is designed to delay ovulation, so if it has already started, it won’t work.
Can I have unprotected sex after using the morning after pill?
EllaOne and Levonelle do not continue to protect you against pregnancy. This means if you have unprotected sex after taking the morning after pill, you can still get pregnant.
The morning after pill is not intended to be used as a regular form of contraception, but you can use emergency contraception more than once in a menstrual cycle if necessary.
Can I take the morning after pill more than once in a week?
It is possible to take the morning after pill more than once in a week, but it’s not suitable for regular use. You shouldn’t take Levonelle within 5 days of taking ellaOne and shouldn’t take ellaOne within 7 days of taking Levonelle (or levonorgestrel).
The morning after pill is intended for occasional use in emergencies. This means it should not be used in place of regular methods of contraception.
If you take it more than once in a menstrual cycle there is a higher chance of it upsetting your menstrual cycle.
The morning after pill has more side effects, is less effective, and is more expensive over time than regular contraception. You should speak to your nurse or doctor about regular contraceptive methods like the pill or condoms if you plan on having regular sex.
Sources
ellaOne 30 mg – Patient Information Leaflet (PIL) (June 2021) EMC (Accessed 19 April 2022)
Emergency contraception | NHS Inform (November 2021) NHS Inform (Accessed 19 April 2022)
Emergency contraception | Terrence Higgins Trust (December 2021) Terrence Higgins Trust (Accessed 19 April 2022)
Emergency contraception (morning after pill, IUD) (February 2018) NHS (Accessed 19 April 2022)
How effective is emergency contraception? (August 2019) NHS (Accessed 19 April 2022)
Levonelle 1500 microgram tablet – Patient Information Leaflet (PIL) (January 2020) EMC (Accessed 19 April 2022)
Morning after pill – Chelsea and Westminster Hospital NHS (2022) NHS (Accessed 19 April 2022)
What is the difference between the ‘morning after pill’ and the abortion pill? (2022) MSI Reproductive Choices (Accessed 19 April 2022)
https://www.fsrh.org/documents/ceu-clinical-guidance-emergency-contraception-march-2017/ (accessed 16/6/22)
Top tips for taking the morning after pill
1. The sooner you take the morning after pill, the better.
Don’t leave any more time than necessary between having unprotected sex and taking the morning after pill. The sooner you take it, the more likely it is to be effective.
2. If you have diarrhoea or vomiting after taking it, consult a doctor.
If you are sick or have severe diarrhoea within 3 hours after taking the morning after pill, there is a risk that it won’t work. If this happens, you need to consult a doctor or pharmacist as soon as possible to check whether you need to take a second pill.
3. Make sure you mention any medication you are taking or have taken recently and any medical problems you suffer from to your pharmacist or doctor.
Certain medications and remedies can stop the morning after pill from working. Before you take the morning after pill, inform your prescribing doctor or your pharmacist of any medication you have recently taken. Suffering from certain health conditions may mean that one type of morning after pill is more suitable for you.