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Home / Morning-After Pill / Does the morning after pill always work?

Does the morning after pill always work?

Find out how to get the most out of emergency contraception

The right emergency contraception can save you any fear of unintended pregnancy. Whether you forgot to take your normal contraception or a barrier contraceptive failed, emergency contraception is always readily available.

However, when it comes to important medications, it’s natural to question how effective they are. This is especially true for all types of emergency contraception. The good news is most methods of emergency contraception are clinically proven to prevent pregnancy, so you shouldn’t have any doubts.

Whilst there are several rare occasions which can alter the effectiveness of a given contraceptive, these situations are entirely avoidable! There’s most likely an emergency contraceptive that is right for you.

Keep reading to find out how effective the different types of emergency contraception are, reasons it may not work and what you can do to get the most out of your emergency contraception.

What is emergency contraception?

Emergency contraception is a form of contraception that you take after unprotected sex, if you miss a contraceptive pill or a barrier contraceptive (a condom) fails. There are two main types of emergency contraception available.

Morning After Pill

The most popular method is known colloquially as the ’morning after pill’ and is available over-the-counter and on prescription. There are two types of emergency contraceptive pills available.

The first type are oral progestogen-only emergency contraceptives, known as levonorgestrel, a synthetic form of progesterone. It is a hormonal treatment available over-the-counter, often under several brand names including Levonelle (sometimes known as Levonelle One Step) and Plan B. You can typically buy these over-the-counter at pharmacies.

The other type is a selective progesterone receptor modulator (SPRM) otherwise known as ulipristal acetate. It works by affecting the progesterone receptors and is only available on prescription and over-the-counter under several brand names, including ellaOne and Ella.

They both work similarly in that they both affect how progesterone works in your body to slow and prevent ovulation during your menstrual cycle. They only differ on when they can be used. Levonorgestrel pills have to be taken within 72 hours after intercourse (but best chances are within 12 hours), whilst ulipristal acetate pills can be taken up to 5 days after.

Single pill in orange foil packaging on blue background

Emergency IUD

The other type of emergency contraception is known as ‘the copper coil’, otherwise known as the copper IUD (intrauterine device). These are small, T-shaped plastic devices that are inserted directly into your uterus (womb). Whilst similar to the hormonal IUD (sometimes known as the IUS, intrauterine system), only the device made of copper is effective for emergency contraception.

Copper IUDs work by releasing copper into the uterus, which alters your cervical mucus. This makes it more difficult for sperm to reach the egg and survive and also stops a fertilised egg from being able to implant itself in the uterus.

An IUD can be used as your main contraception, but if it is within a 5-day period after unprotected sex, it can also be used as emergency contraception. After you have had your emergency IUD installed, you can keep it as your main form of contraception or can be removed during your next period.

It may seem worrisome to have something inserted, but they are perfectly safe and effective for a majority of women! The only women they are not suitable for are those who are allergic to copper, have PID (pelvic inflammatory disease), a blood clotting disorder or an active STI (sexually transmitted infection).

 Two IUDs on a pink background

Which is the most effective method?

All methods of emergency contraception are clinically proven to prevent unwanted pregnancy, however they slightly differ in their effectiveness.

The Morning After Pill

The morning after pill is the most accessible method of emergency contraception, but how effective is it? Fortunately, both Levonelle and ellaOne have low pregnancy rates when taken correctly.

However, ellaOne tends to be slightly more effective. A 2010 study Trusted source PubMed Government Source Database of Biomedical Research Go to source compared the effectiveness of the two pills by analysing multiple clinical trials. They found that pregnancy rates when taking levonorgestrel were between 2.2 - 2.8 % whilst the rates when taking ulipristal acetate were around 1.4 - 1.8%.

The difference in efficacy is so small so, regardless what pill you take, you’re guaranteed over 90% protection, as long as you take it exactly as instructed.

Copper Coil

But what about the coil? The copper IUD has actually been found to be the most effective emergency contraception available. When inserted within 5 days of unprotected sex, it is 99.9% Trusted source National Center for Biotechnology Information (NCBI) Government Source Biomedical Research and Literature Go to source . This means less than 1 in 1,000 women using the IUD as emergency contraception get pregnant.

However, many women don’t even know how effective it is. Research conducted by the FSRH Trusted source Faculty of Sexual and Reproductive Healthcare Professional Organization Go to source (Faculty of Sexual Reproductive Health) found that only 13% of women aged 18-45 could identify that it was even available as a form of emergency contraception. Whilst arguably the least accessible out of the two, it is the most effective option.

When is the ‘morning after pill’ not effective?

So, all types of emergency contraception significantly lower your risk of pregnancy, with only a small difference in efficacy rates between them. However, there are rare occasions where the pill might not work where the IUD does. Here are four reasons why the morning after pill may not work for you.

1. You don’t follow the instructions

This may seem like the most obvious reason, but it is the most avoidable. It is imperative that you follow the instructions when taking your birth control pills to ensure they work. This includes making sure you take them within the specified time and not having unprotected sex before your next period. If in doubt, you should use barrier contraception until your next period.

You should also take caution if you throw up within 3 hours of taking it. Vomiting can be a side effect of both emergency oral contraceptives, but can mean the medicine is not absorbed by your body. If it occurs, you should speak to your pharmacist or doctor as soon as possible because it may mean the medication will not work.

You should always follow the instructions in the patient information leaflet as well as the advice from your doctor or pharmacist.

Woman in bed reading medicine leaflet before taking

2. You take it after you have ovulated

The time you take the pill can influence its effectiveness. All of the methods above require you to take it within 3 - 5 days after you had sex, but the sooner you take it the more effective it is.

This is because you’re more likely to take it before ovulation. Ovulation involves the release of an egg from your ovary and into your fallopian tube which the morning after pill is designed to delay. The longer you wait to take it, the more likely you will have ovulated and the morning after pill will not work.

One way to combat this is to track your menstrual cycle. This way, you can track your ovulation and fertile window so you can use your contraception effectively. In Robert Hatcher’s handbook “Contraceptive technology”, it is suggested that pills like Levonelle are most effective between days 9 - 12 of your cycle, whilst pills like ellaOne are most effective between days 9 - 14. However, the time of a woman's fertile and ovulation windows can vary each cycle, so these estimates are not the same for everyone.

The copper coil is the only form of emergency contraception that is effective after you ovulate. This is because it doesn’t target ovulation to prevent pregnancy.

The word ‘ovulation’ handwritten and circled on a calendar

3. You have a high BMI

Your body weight may also slightly alter emergency contraception effectiveness. A study Trusted source PubMed Government Source Database of Biomedical Research Go to source conducted in 2011 found that obese women (women with a BMI of 30 or over) had a slight increased risk of pregnancy when taking levonorgestrel. Whilst later studies Trusted source PubMed Government Source Database of Biomedical Research Go to source have suggested more research into the area is needed, women who are overweight still have to be advised that this pill may not work as well for them. However, the morning after pill still has higher efficacy rates than not taking anything.

ellaOne tablets may be a better solution for these women. Whilst there is a similar trend reported for tablets containing ulipristal acetate, the results from various studies Trusted source ScienceDirect Peer-reviewed Journals Multidisciplinary Research Go to source demonstrate a much more finite difference in efficacy rates between women with high BMIs and women with lower BMIs. The results were not statistically significant.

If you have a higher BMI and are still unsure if the morning after pill will work for you, then get the copper IUD. Weight has no effect on the IUD and is safe for the majority of women.

Women’s feet stepping on scales

4. You take other medicines

Certain medications can actually make the morning after pill less effective. This is the case with many prescription medications but it is equally as pertinent for emergency contraception.

Certain antibiotics, anti-seizure medications, sedatives, antifungals as well as St John’s Wort can all make your emergency contraception pill less effective. In addition, if you usually take a hormonal contraceptive (the combined pill, mini-pill, patch or ring), you will also need to modify your schedule after taking the morning after pill.

If you take either morning after pill, you can start using your regular hormonal contraception straight away. However, it is sometimes recommended to use barrier contraception as well as your hormonal contraception. This is because the morning after pill may alter the effectiveness of your regular contraception. Instructions may vary across different sources (e.g patient information leaflets and online resources) so it’s important you follow the instructions of the healthcare professional prescribing you.

Whilst this seems worrying or confusing, your doctor or pharmacist will always check your medical history to make sure it’ll work for you. You can always check the patient information leaflet of the pill you're prescribed; it will contain a list of all the medications that may affect your contraception.

Pharmacist holding a box of medicine blister packs

How do I get emergency contraception?

The copper IUD is the most effective form of emergency contraception without a doubt. It is available for free from your GP, sexual health clinics and GUM (genitourinary medicine) clinics and requires an appointment to install it. They should be fitted 5 days after intercourse.

IUDs aren’t suitable for everyone however. So if they’re not right for you or you’re not able to get one fitted, the morning after pill can be bought over-the-counter at most pharmacies. Levonelle can be purchased within 3 days of intercourse whilst ellaOne can be purchased within 5.

If you want to save the hassle of getting an appointment and have your contraception delivered directly to your doorstep, you can buy both Levonelle and ellaOne here from euroClinix. We deliver with discreet packaging and next-day delivery so you can be protected straight away.

At euroClinix, you can also order 3 pills at a time. Meaning that after you have taken one for immediate use, you still have two pills spare if your normal contraception doesn’t work in the future, whether you get sick or a barrier contraceptive breaks.

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Medically reviewed by Dr. Caroline Fontana Written by our editorial team Last reviewed 30-09-2023
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