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How Effective is the Morning After Pill?
The morning after pill can prevent pregnancy if taken within the recommended timeframe after unprotected sex. How effective is it and what can reduce its effectiveness? Find out how to use it and how to avoid getting pregnant.
Last reviewed: 11/06/2020 by Dr Simran Deo
Contents
- How long after having unprotected sex should I take the morning after pill?
- What can make the morning after pill less effective?
- Does my weight affect the effectiveness of the morning after pill?
- Can you get pregnant after taking the morning after pill?
- Can you have unprotected sex after taking the morning after pill?
- Who can take it?
How long after having unprotected sex should I take the morning after pill?
The two most common emergency contraceptive pills are Levonelle (the generic version of which is called Levonorgestrel) and EllaOne (ulipristal). The time frame within which they work differs:
Levonelle is 97-99% effective at preventing pregnancy when taken within 72 hours of sex and before you have ovulated. It should be taken as soon as possible after unprotected sex to be most effective.
EllaOne needs to be taken within 120 hours (5 days) of unprotected sex and before ovulation. It is 98-99% effective at preventing pregnancy which is more effective than Levonelle.
An emergency copper coil, fitted within 5 days of your latest ovulation date, is the most effective method of emergency contraception (>99.9% effective at preventing pregnancy).
The morning after pill is less reliable at preventing pregnancy than using regular contraception such as the pill or the condom. You should only take it in emergencies and use contraception every time you have sex.
There are a number of factors which can reduce its effectiveness.
What can make the morning after pill less effective?
There are certain things which can make the morning after pill less likely to work, such as certain medical conditions and medications:
Vomiting: You may experience nausea and vomiting as morning after pill side effects. If you vomit or have diarrhoea within 3 hours of taking the pill then there is a high chance that it won’t have been absorbed by your body. In this case, speak to a doctor or pharmacist. You will need to take another morning after pill to prevent pregnancy.
Other medications: Some medications can stop the morning after pill from working. This includes the following medications and remedies:
- St John's Wort
- HIV drugs such as Ritonavir or immune system suppressants
- TB treating drugs such as Rifabutin
- Barbiturates and other medications used to prevent seizures
- Certain antifungal medications
- Proton pump inhibitors like omeprazole can make EllaOne less effective (but do not affect Levonelle)
- Progesterones (the hormone in contraceptive pills, implants, injections, certain coils, Levonelle, period delay medication and some HRT) taken in the 7 days before or the 5 days after taking EllaOne can make EllaOne less effective
If you decide to take EllaOne it’s important that you don’t start any progesterone containing medication (this includes your oral contraceptive pill) for at least 5 days afterwards. If you usually take a contraceptive pill you will need to use condoms during these 5 days if you have sex and then for the period that it takes for your pill to become effective.
Does my weight affect the effectiveness of the morning after pill?
If you have a BMI of more than 26 or weigh more than 70kg Levonelle is likely to be less effective and you should take EllaOne or have an emergency copper coil fitted if you are able to. Your doctor or pharmacist may prescribe a double dose of Levonelle.
If you have a BMI more than 30 or weigh more than 85kg EllaOne is less likely to be effective and an emergency copper coil would be recommended (a double dose of EllaOne is never recommended).
Can you get pregnant after taking the morning after pill?
As with most contraceptives, there remains a risk that you could still become pregnant. However, if you take the morning after pill within the correct time frame, this risk is small. In order to reduce your risk of pregnancy you should take the pill as soon after sex as possible.
It is not unusual for the morning after pill to affect your periods. You may find that your next period is lighter or late or earlier than normal. You should take a pregnancy test 3 weeks after any episodes of unprotected sex to make sure you are not pregnant. If you miss your next period or your next few periods are very light, you should visit a doctor.
Can you have unprotected sex after taking the morning after pill?
The morning after pill does not prevent pregnancy if you have unprotected sex after taking it. It is important that you use contraception the next time you have sex.
Who can take it?
The morning after pill is not suitable for everyone. If you suffer from any of the following, you may be advised not to take it:
- severe liver disease
- severe asthma (EllaOne only)
- a stomach condition or a condition of the digestive system
- allergies to any of the ingredients
You should speak to a doctor or pharmacist and check the manufacturer's instruction leaflet before taking the morning after pill to check which pill would be most suitable for you and for a full list of potential side effects.
Sources
EllaOne 30mg tablet (2017) EMC [accessed 9 July 2020]
Levonelle 1500mg tablet (2018) EMC [accessed 9 July 2020]
CEU clinical guidance: emergency contraception (March 2017, amended December 2017) FSRH [accessed 9 July 2020]
CEU clinical guidance drug interactions with hormonal contraception (January 2017, reviewed 2019) FSRH [accessed 9 July 2020]
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.