Does the Morning After Pill Work? Real UK Experiences & Clinician Guidance

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The Short Answer at a Glance

Yes. Emergency contraception (the “morning after pill”) can work very well, especially when taken as soon as possible after unprotected sex. It works by delaying ovulation (the release of an egg) so sperm can’t fertilise it. Side effects like spotting, cramping, nausea, or a slightly early or late period are common and don’t necessarily mean it has failed. If your period hasn’t arrived within 3 weeks, it’s important to take a pregnancy test.


Who this guide is for


This guide is for people in the UK who’ve taken, or are thinking about taking, the morning after pill and want a clear explanation of how effective it is, what to expect afterwards, and when to do a pregnancy test or seek further help.

Needing the morning after pill can feel scary. You might be worrying about timing, whether you chose the “right one”, or what every twinge and late period means. Many people feel anxious during the days between taking emergency contraception and their next period.

Emergency contraception (often called EC or the “morning after pill”) is designed to reduce the chance of pregnancy after unprotected sex or contraceptive failure. It doesn’t end a pregnancy that’s already started, but it can greatly lower the risk if used correctly and promptly.

In this guide, we’ll walk through real experiences, how EC actually works, how effective EllaOne and Levonelle are, what normal side effects look like, and when to take a pregnancy test or seek more support.


Key Takeaways

  • Emergency contraception works best the sooner you take it
  • Periods can arrive earlier or up to 7 days later than usual
  • Spotting, mild cramps, breast tenderness, and nausea are common
  • If your period hasn’t arrived within 3 weeks, take a pregnancy test
  • Effectiveness is affected by ovulation timing (when the egg is released), BMI (your weight-to-height ratio), vomiting, and some medicines
  • EllaOne (Ulipristal ) works up to 120 hours (5 days) after unprotected sex 
  • Levonelle (Levonorgestrel) up to 72 hours (3 days) after unprotected sex.
  • EllaOne  tends to be more effective than Levonelle when you’re closer to ovulation



1. Real Experiences With the Morning After Pill


Emergency contraception often comes with a wave of “What if?” thoughts. Real experiences vary a lot and can be confusing if you’re not sure what’s normal.

“I took EllaOne 12 hours after sex. My period was a week late.”
“Levonelle made me feel sick and I panicked thinking it failed.”
“My period was totally normal after EC. I just needed reassurance.”

These experiences are all common. Some people notice almost no changes to their cycle, while others see spotting, cramps, or a late period. On their own, these symptoms do not mean the pill hasn’t worked.

Side effects and cycle changes are normal after EC and don’t automatically mean it has failed.

What matters most for effectiveness is timing, which type of pill you took, and a few key health factors. We'll come to those shortly.


2. How Emergency Contraception Actually Works

Emergency contraception does not end an existing pregnancy. Instead, it works earlier in the process.

Most morning after pills work by:

  • Delaying or blocking ovulation (the moment an egg is released from the ovary)
  • Making it less likely that an egg and sperm will meet at the right time

If ovulation has already happened and fertilisation has occurred, the pill is much less likely to help, which is why timing is so important.

From clinical experience, many people feel very anxious if their period arrives later than usual. A delay of up to 7 days is extremely common and often settles without any problem.

Effectiveness depends on:

  • Whether ovulation has happened yet
  • How quickly you take it after sex
  • Which pill you use (EllaOne vs Levonelle)
  • BMI (your weight-to-height ratio)
  • Vomiting soon after taking it
  • Certain medicines that speed up how your body clears hormones (enzyme-inducing medicines, such as some epilepsy or TB treatments)


EllaOne tends to stay effective closer to ovulation compared with Levonelle, which is more time-sensitive.

EC works by delaying ovulation; it can’t undo a pregnancy that’s already started.


3. How Effective Is the Morning After Pill?


No emergency contraception is 100% effective, but both main options used in the UK work well when taken correctly.

EllaOne (ulipristal acetate)

  • Up to 98% effective when taken soon after sex
  • Can be taken up to 120 hours (5 days) after unprotected sex
  • More effective than Levonelle when you are closer to ovulation
  • Less affected by BMI than levonorgestrel-based pills

 

Levonelle (levonorgestrel)

  • Up to 95% effective when taken within 24 hours
  • Can be used up to 72 hours (3 days) after unprotected sex
  • Works best the earlier it’s taken (ideally within 12–24 hours)
  • Effectiveness may be reduced at higher BMI, so EllaOne is often preferred in that situation


Pregnancies after EC usually happen when:

  • The pill is taken too late
  • Ovulation has already happened
  • Vomiting occurs within 2 hours and no repeat dose is taken
  • You’re on enzyme-inducing medicines that reduce effectiveness


“I felt better once I understood that I’d taken it within a few hours. I’d given myself the best possible chance.”

Both EllaOne and Levonelle work well, but EllaOne is usually preferred later in the cycle or with higher BMI.


4. What to Expect After Taking Emergency Contraception


After EC, your body can react in a few different ways. Most changes are mild and short-lived.

Common, temporary side effects include:

  • Nausea or mild vomiting
  • Light spotting or breakthrough bleeding
  • Mild cramping or period-like pains
  • Breast tenderness
  • Tiredness or feeling “off” for a day or two
  • A period that comes up to 7 days earlier or later than usual


“I felt a bit queasy and had some spotting, but my period arrived a few days late and was otherwise normal.”

Feeling “off”, spotting, or having a slightly early or late period is normal after EC.

If vomiting happens within 2 hours of taking the pill, you should contact a clinician or pharmacist, as you may need a second dose.


5. When to Take a Pregnancy Test


The most important safety check after using the morning after pill is timing a pregnancy test properly.

You should take a test if:

  • Your period hasn’t arrived within 3 weeks of taking EC, or
  • You’re unsure whether bleeding you’ve had counts as a proper period, or
  • You notice ongoing pregnancy-type symptoms (such as nausea, breast tenderness, or tiredness) that feel different or persistent


If the test is positive, seek medical advice promptly to discuss next steps and to rule out ectopic pregnancy (a pregnancy outside the womb, which is rare but serious).

“My period was late and I was panicking. Taking a test at three weeks finally gave me a clear answer.”

If there is no period within 3 weeks, a pregnancy test is essential, even if you’ve had some spotting.


6. When the Morning After Pill May Not Work as Well


Emergency contraception is still worth taking as soon as possible after unprotected sex, but it may be less likely to work in certain situations:

  • Taken close to or after ovulation
  • Vomiting within 2 hours and no repeat dose taken
  • Taking enzyme-inducing medicines (medicines that speed up how the liver breaks down hormones, such as some epilepsy, HIV, or TB treatments)
  • Higher BMI, particularly with levonorgestrel-based pills (Levonelle), where EllaOne or a copper IUD may be preferred


“I was on long-term medication, so my clinician recommended EllaOne and explained why it was a better option for me.”

The pill is still worth taking, but timing, weight, and medicines can affect how well it works.

If you’re on long-term medication or have a very high risk of pregnancy from this episode, a clinician may discuss a copper IUD (a non-hormonal coil) as the most effective form of emergency contraception.


7. Next Steps After Taking Emergency Contraception


Once you’ve taken EC, it helps to have a simple plan for what comes next:

  • Use condoms for at least 7 days-This protects against pregnancy while your usual contraception “catches up” or starts working again.
  • Restart your regular contraception-Unless you’ve been told otherwise, you can usually restart your pill, patch, or ring the next day. Your clinician or pharmacist will explain any specific timing rules.
  • Consider long-term contraception-If you’ve needed the morning after pill more than once, it might be time to talk about a more reliable method (such as the implant, IUD, or injection).
  • Watch for unusual symptoms-Seek medical advice if you have heavy or prolonged bleeding, severe pain, fever, or no period by 3 weeks.


“Needing EC was the nudge I needed to sort long-term contraception. I feel much more relaxed now.”

Emergency contraception is a useful backup, but a good long-term method reduces stress in the future.


Frequently Asked Questions


Does the morning after pill always work?

No method is 100% effective, but EllaOne and Levonelle are both highly effective when taken as directed and as soon as possible after unprotected sex.

Can the morning after pill delay my period?

Yes. Your period may come up to 7 days earlier or later than expected. Mild spotting is also common.

Do side effects mean it’s working or not working?

Side effects like nausea or spotting don’t tell you if EC has worked. They are common and usually settle on their own.

Is EC the same as an abortion pill?

No. Emergency contraception does not end a pregnancy. It works by delaying ovulation to prevent a pregnancy from starting.

When should I seek urgent help?

Seek urgent care if you have severe lower tummy pain, very heavy bleeding, feel faint or unwell, or if you get a positive pregnancy test and also have pain or bleeding.

Safety Section

Emergency contraception is generally safe for most people, but it’s important to:

  • Tell your clinician or pharmacist about all medicines you’re taking
  • Mention any history of liver problems, severe asthma, or allergies
  • Seek urgent help if you have severe abdominal pain, very heavy bleeding, or feel faint or unwell after taking EC


Guidelines from organisations like the CoSRH (College of Sexual and Reproductive Healthcare), NHS, and WHO support the use of emergency contraception as a safe, time-sensitive option when taken correctly.

SwiftMedi clinicians always review your medical history and current medicines before prescribing EC.


Safety Disclaimer


This article provides general information and isn’t a substitute for medical advice. Always speak with a healthcare professional about your personal situation. SwiftMedi only supplies treatment following a clinical assessment, and completing a consultation doesn’t guarantee a prescription. Seek medical help if your symptoms worsen or you’re concerned about your health.


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