Your guide to emergency contraception and the morning after pill

Maddie Braidwood - The Lowdown

by Maddie Braidwood · Aug 16, 2020

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Reviewed by Dr Becky Mawson on Oct 22, 2021

Let's talk about emergency contraception... starting with when you do and DON'T need to use it.

TLDR… what’s the lowdown?

  • The morning after pill is unlikely to work if you have already ovulated and the copper IUD is the most effective form of emergency contraception
  • Some morning after pills contain the same progestogen hormone as many standard contraceptive pills: Levonorgestrel
  • If you are overweight, you may need a higher dose of the morning after pill
  • The morning after pill does not affect fertility, and there is no limit to the amount of times it can be taken
  • Consider whether starting an ongoing method of contraception or switching from your current method may be more effective or easier to manage.


Information, research and education surrounding oral contraception has been growing over recent years, with more women seeking to better understand the pill and the effects it can have on their bodies. (We don’t want to take too much credit for this, but, y’know… we’ve done some stuff). 

While we’re all getting more clued up about our everyday contraceptives, however, one pregnancy-prevention method has received less of the limelight. 

The morning after pill is a form of emergency contraception, used after unprotected sex or when birth control has failed, and taken in the hours or days following sexual intercourse. Whether you’ve used it before or not, you probably have some idea of what the morning after pill is all about – but there might be some things you’re unsure of.

We asked women what they thought when they heard the words ‘morning after pill’, to see whether they had the full picture. Their responses were pretty varied: 

“It’s most effective when taken immediately”

“You can order it online nowadays, I see ads for it all the time”

“You have to take it within 36 hours”

“You have to take it within 24 hours”

“You can only take it three times in your life” 

“After three days it doesn’t work”

Some of these responses are true, but most are variations of the truth that we’ve all probably heard since we were teenagers and the first Brook clinic opened in our local town centre. Emergency contraception isn’t something we’re told a huge amount about, so if you’re a bit confused, you’re not alone. One woman, when asked what she knew about the morning after pill, said: “absolutely nothing”

So, let’s get into it.

How does the morning after pill work?

The menstrual cycle

In order to understand how the morning after pill works, we first have to know what happens during the menstrual cycle. We’ve got a really brilliant piece about this (if we do say so ourselves), which gets into the details of all the phases of your cycle. For the purposes of understanding the morning after pill, however, we’ll briefly go over just the follicular phase here.

The first day of your period signals the beginning of the first phase of your cycle: the follicular phase.  During the follicular phase, when oestrogen and progesterone levels are low, follicular stimulating hormone (FSH) rises, causing the most advanced follicle (a sack of fluid inside your ovary that contains an egg) to mature. When the follicle is big enough it produces large amounts of oestrogen which triggers another hormone (stay with us) called luteinising hormone (LH), which tells the follicle to release the egg. Voilà – ovulation!

menstrual cycle the lowdown

How the morning after pill affects the menstrual cycle

There are lots of brands of morning after pill on the market at the moment including Levonorgestrel, Ezinelle, Levonelle One Step, and ellaOne. All of these pills contain a synthetic hormone called levonorgestrel, except ellaOne, which contains ulipristal acetate.

Sperm can stay alive in the female genital tract for about 5 days after sex.  If ovulation occurs within those 5 days, fertilisation could take place and a woman is at risk of pregnancy.

Strangely enough, the scientists still can’t agree on exactly how levonorgestrel works. We do know, however, that it delays the release of an egg (ovulation), meaning that any sperm present in the body will most likely die before an egg appears and they have the chance to fertilise it. 

The function of ulipristal acetate, on the other hand, is clearer: it stops the normal functioning of progesterone and prevents the surge of LH (the one that tells the follicle to release its egg), and so delays ovulation. Similarly to levonorgestrel, an egg is released later on, giving the sperm time to say their goodbyes before the egg arrives!

It is important to mention that the morning after pill isn’t an abortion pill, which makes sense; without ovulation, pregnancy cannot occur. Some research exploring the precise mechanisms of emergency contraceptive pills suggests that the pills could have an effect on an egg that is already fertilised. However, a judicial review in 2002 concluded that pregnancy begins at implantation (where a fertilised egg embeds itself into the womb lining). All forms of emergency contraception therefore work before implantation occurs rather than disrupting established implantation.

Talk to one of our friendly doctors 

When should I use the morning after pill?

The morning after pill can be used after unprotected sex to prevent pregnancy. Unprotected sex is any sex during which contraception is not used, or not used correctly or during which contraception has failed. This could be a broken condom or forgotten pills – if your contraception has not worked or been taken as it is supposed to, the morning after pill may help to prevent a potential unintended pregnancy.   

When might the morning after pill not work?

If you take it after you ovulate:

This is really, really important, and is something that very few women know about. Earlier, we explained that the morning after pill interferes with our natural cycle and causes an egg to release later than it normally would. If that egg is already released when you have sex, however, the hormones in the morning after pill may not be able to do anything about it. Essentially, if you’re past the ovulation stage of your cycle or fertilisation has occurred, the morning after pill will not work and you may become pregnant. This is why it’s so important to do a pregnancy test 3 weeks after taking a morning after pill.

If you remember, though, there’s a debate in the scientific community about the effects of the morning after pill following ovulation. So you may want to take the morning after pill, even if you think you may have already ovulated. Although the general consensus still seems to be that it’s primary function is to delay the release of an egg. 

If you’re overweight:

Research has found that the morning after pill is less likely to work in women with a BMI of 26 or above, or if you weigh over 70kg (even with a normal BMI). Studies suggest that doubling the dose can increase the effectiveness of the levonorgestrel morning after pill and this has been added to the guidelines for emergency contraception. In women with a BMI of 26 or above or who weigh over 70kg (and a copper coil is not suitable) use ellaOne, or a double the dose of the levonorgestrel morning after pill can be used. This is something you can discuss with your doctor or pharmacist. 

How long after sex should I take the morning after pill?

The NHS states that Ezinelle, Levonelle One Step and Levonorgestrel must be taken within 72 hours (three days) of unprotected sex. ellaOne can be taken up to 120 hours (five days) after unprotected sex. 

Sex is classed as unprotected not only if no contraception is used, but also if the contraception you are using has failed (such as a broken condom or a forgotten pill). 

How effective is the morning after pill?

The earlier you take the morning after pill, the lower your chances of becoming pregnant. Remember that current advice states that the pill must be taken before ovulation in order to be effective, so the later you take it the more risk you have of ovulating and the more likely it is the pill won’t work.

Researchers looked at all the evidence surrounding the morning after pill and found that ellaOne was more effective at preventing pregnancy than levonorgestrel containing pills. They found that 1-2% of women will become pregnant after using ellaOne, compared to 0.6-2.6% of women who take another morning after pill.

However, if you’re REALLY keen to not get pregnant, less than 0.1% of women get pregnant after having the copper coil fitted as emergency contraception.

As we said earlier, the effectiveness of the morning after pill might be reduced if you have a high BMI. This is something to consider when discussing your options with your healthcare provider

If you vomit within two hours of taking a levonorgestrel containing pill, or within three hours of taking ellaOne, you will need to take another dose or have a copper coil (IUD) fitted to prevent pregnancy. 

The copper coil (IUD) as emergency contraception

Many women aren’t aware that the MOST effective form of emergency contraception is actually the copper coil (IUD). This can be fitted up to five days after unprotected sex, and only 0.1% of women who choose this method become pregnant. An added benefit of the coil is that once it is in place, it can be left for up to ten years (depending on the brand of coil), providing an emergency solution alongside long-term contraception. Win-win

The great thing about the copper coil is that if you have a regular cycle, it can be fitted up to 5 days after you have ovulated. That means that you could have had multiple episodes of unprotected sex in your cycle and still get the emergency coil fitted.

If there is concern about sexually transmitted infection the clinic will offer you antibiotics at time of fitting as well as screening.

Access to an IUD as emergency contraception at your GP might be limited, but all sexual health clinics should be able to offer it to you. Find a sexual health clinic here. 

You can read more about the coil in our dedicated guide. 

How long does the morning after pill take to work?

The morning after pill should work almost immediately to delay ovulation. It is important you don’t use the morning after pill as a preventative measure – i.e. don’t think you’re safe to have unprotected sex after you’ve taken it. Sperm can survive inside your body for a few days, so having unprotected sex again after you’ve taken it could lead to pregnancy. You will need to consider emergency contraception again for any further episodes of unprotected sex.

What should I expect when taking the morning after pill?

Side effects

Most women experience no side effects when taking the morning after pill, and there are no serious or long-term side effects associated with it at all. However, the NHS states that you might experience:

  • Headaches
  • Tummy ache
  • Changes to your next period – we discuss this more below
  • Feeling nauseous or vomiting – remember that if you vomit within two hours of taking Levonorgestrel or within three hours of taking ellaOne, you’ll need to make another visit to your healthcare provider to get a second dose of the morning after pill.

Your period may be earlier, later, lighter, heavier or more painful than usual after taking the morning after pill. This is because, when taken at the correct time, the morning after pill delays ovulation and, as a result, alters the timings of our natural cycle. This is temporary, and should only affect your next period before things return to normal.

Interacting medicines

There is a large (and rather overwhelming) list of medicines that can interact with the morning after pill.

The NHS page for emergency contraception states that it should not be taken if you have severe asthma, take St John’s Wort, take some medicines for epilepsy, HIV or tuberculosis, take medicines for stomach acid, or are taking certain types of antibiotics. These medicines won’t make it dangerous for you to take the morning after pill, they just might make it less effective, and your dose may need to be increased.

If you’ve used combined hormonal contraception (i.e. the combined pill, patch or ring) or the progestogen-only pill in the 7 days prior to using emergency contraception, the effectiveness of ullipristal acetate in ellaOne could theoretically be reduced so healthcare professionals would advise you to consider the copper IUD or a morning after pill containing levonorgestrel. If you require emergency contraception because your injection, implant or coil has run out and needs replacing, check this with your doctor.

If you are at all unsure, talk to your healthcare provider about the medications that you are taking before choosing the morning after pill.

How do I know if the morning after pill has worked, and should I take a pregnancy test?

Unfortunately, the only way to really know whether the morning after pill has worked is to patiently wait for your next period to come along. Do remember that the pill itself can make your period late, so try not to worry if it doesn’t arrive on time. As the pill can affect your period, or cause spotting or bleeding, it is recommended that you take a pregnancy test three weeks after taking the morning after pill and don’t rely on your period as a sign you’re not pregnant.

What should I do if the morning after pill doesn’t work? 

If you do find yourself pregnant after taking the morning after pill, it can be unexpected and overwhelming. Consider speaking to someone you trust, and remember that this isn’t something you have to face alone. There are brilliant organisations and resources available to help you through. The British Pregnancy Advisory Service (BPAS) offers counselling if you need someone to talk to about an unintended pregnancy, and will go through your options with you to ensure you’re making the best choice for you. 

If you’d rather speak to your doctor, they can also discuss the options available to you, and can refer you on to services that might be helpful, whatever you decide.

Can the morning after pill make you infertile? 

No. There are many myths surrounding the use of the morning after pill, but very few of them are true. The morning after pill will not affect your fertility in any way.

Is it true that you can only take the morning after pill three times in your life?

Nope! Doctors and healthcare providers recommend that you don’t take the morning after pill too often, which has caused rumours about its safety. In reality, the morning after pill has no long-term effects on your body, so can be used as many times as you need. 

The reason you might be advised to refrain from taking it too often is because there are other contraceptive choices available to you that are far more effective and easier to manage.

If your current method isn’t working for you (broken condoms or forgotten pills for example), consider speaking to your doctor or nurse about something that might be more suitable for you. Or even better, book in with one of our fabulous medics from The Lowdown Team! Although we don’t offer emergency appointments, our medics can give you individualised advice on ongoing contraception.

How much does the morning after pill cost?

You can get the morning after pill for free from most healthcare providers, such as sexual health clinics and your GP. If you go to a pharmacy, you might have to pay around £25 for Levonorgestrel or £35 for ellaOne. You can order the morning after pill cheaper online from places like Superdrug and the ellaOne website. Be sure to check that the website you’re using is reputable before ordering. We will be adding the morning after pills to The Lowdown’s online ordering service later this year.

However remember there may be a delay in postage and delivery so make sure this won’t push you beyond the 72 or 120 hour window after unprotected sex in which you have to take it. Remember the earlier you take it the more effective it is likely to be

If you are under 16, you will need a prescription from your doctor to buy Levonorgestrel, but over-16s can buy it without a prescription. Anyone can buy ellaOne without a prescription.

The NHS provides more information about the services that offer free and paid access to the morning after pill. 

Can I just start using a standard contraceptive pill straight away instead?

If you begin taking a contraceptive pill within the first five days of your period, you are immediately protected against pregnancy. Beginning your contraception on any other day of your menstrual cycle is called ‘quick starting’. If you decide to ‘quick start’ a standard contraceptive pill, you will need to use another form of contraception for the first seven days. All methods of contraception can be ‘quick started’ at any time if you’re not at risk of pregnancy. 

If you have recently had unprotected sex, you should consider emergency contraception if you want to avoid an unintended pregnancy. There may be a risk of a very early pregnancy but quick starting your contraception at this point is an option if a pregnancy test is negative. In this case you will be advised to do a pregnancy test three weeks after the last episode of unprotected sex. The available evidence shows there is no harmful effect of hormones from contraception on an early pregnancy. 

If you have used the emergency contraception pill ellaOne (containing ullipristal acetate) wait 5 days before quick starting your pill (or other suitable hormonal contraception) and use condoms or avoid sex in the meantime and until your contraception method is effective (for a further 7 days if quick starting the combined pill for example).

There are also many great options, other than the pill for ongoing contraception – take a look at our contraception pages and reviews on The Lowdown!

Low on pills? Order your contraception through The Lowdown

In summary..

Deciding on which contraception to use is enough of a minefield without throwing an emergency into the mix. If you’re clued up about your cycle and know when you ovulate, you might be able to tell whether the morning after pill is right for you when the moment arises. If you’re not, or you think you might be later on in your cycle – or if you just want a more effective, emergency AND long-lasting method of contraception – the coil is a much safer bet. 

The most important thing to remember, though, is that accidents happen to everyone. When things go wrong, you’re never alone, and there are always options available to you. If you’re not sure what to do, consider talking through your options with your doctor or nurse, or book a private consultation with one of in-house GPs to discuss your options with a contraception expert.

  1. Patient, Emergency Contraception
  2. Edelman, A. B., Cherala, G., Blue, S. W., Erikson, D. W., & Jensen, J. T. (2016). Impact of obesity on the pharmacokinetics of levonorgestrel-based emergency contraception: single and double dosing. Contraception94(1), 52–57. 

  3. FSRH Clinical Guideline: Emergency Contraception (2017) Amended 2020. Faculty of Sexual and Reproductive Health. Accessed 5th July 2021 from:

  4. FSRH Clinical Guidline: Quick Starting Contraception (2017). Faculty of Sexual and Reproductive Health. Accessed 3rd July 2021 from:

  5. How effective is emergency contraception? NHS. Accessed 2nd July 2021 from:

  6. Kapp, N., Abitbol, J. L., Mathé, H., Scherrer, B., Guillard, H., Gainer, E., & Ulmann, A. (2015). Effect of body weight and BMI on the efficacy of levonorgestrel emergency contraception. Contraception91(2), 97–104.  

  7. Where can I get emergency contraception? NHS. Accessed 5th July 2021 from:

Maddie is an English Language and Linguistics graduate who is passionate about writing. She writes fun and informative content on the weird and wonderful sides of contraception!