How does the morning-after pill work?

The morning-after pill prevents or delays ovulation. Ovulation happens when your ovaries release an egg into the fallopian tube. When you take the morning-after pill, the pill works to stop your body from releasing the egg so there’s no egg for sperm to fertilise. The morning-after pill stops fertilisation before it can even happen.

Morning-after pills usually contain a synthetic form of progesterone or ulipristal acetate, which prevents progesterone from working normally. They can either delay or stop ovulation. This emergency contraceptive can be up to 98% effective at preventing pregnancy – depending on how soon you take it after unprotected sex.

The morning-after pill does not destroy a fertilized egg and it does not cause an abortion. If you’re already pregnant, it will have no effect. The morning-after pill doesn’t continue to protect against pregnancy, either. Even after taking a morning-after pill, make sure to use another form of contraception for protection.

When should I take the morning-after pill?

Take the morning-after pill as soon as possible. The sooner you take it, the more effective it is. However, certain brands are effective for up to five days after unprotected sex.

Levonorgestrel – sometimes sold as Levonelle or Ezinelle – can be taken up to 72 hours (three days) after sex. EllaOne can be effective for up to 120 hours (five days) after sex.

Who can take the morning-after pill?

Most women can safely take the morning-after pill. This includes girls under 16 years old, women who can’t take daily hormonal contraception, and women who are breastfeeding.

However, some medications can alter the effectiveness of the morning after pill, including:

  • St John’s Wort
  • Some epilepsy medications, like carbamazepine, felbamate, oxcarbazepine, phenytoin, and topiramate
  • Some less commonly used antibiotics and antifungal treatments, like rifampin and griseofulvin

The morning after pill can also be less effective if you’re overweight (ie having a BMI of 30 or higher).

Want to plan ahead?

You can get the morning-after pill for immediate use, or you can order it for later. Head to our easy online consultation to get started!

You shouldn’t rely on the morning-after pill as a regular method of contraception. It’s recommended you only take it once per cycle. Instead, you could consider the daily pill as a regular method of contraception. Hello Eve stocks all UK brands of the daily pill. Using our online consultation, our prescribers can find the most appropriate pill for you and have it delivered straight to your door! Whether you need emergency contraception or daily contraception, always consult a licensed healthcare professional to find the best method for you– regardless of your health or circumstances.

More from our advice centre