How does the morning after pill work?

There are two types of hormonal emergency contraception pills (‘morning after pill’), Ulipristal acetate (ellaOne) and Levonorgestrel (Levonelle).

Levonelle has to be taken within 72 hours (3 days) of sex, and ellaOne has to be taken within 120 hours (5 days) of sex.

Both pills work by preventing or delaying ovulation (release of an egg). Emergency contraception is best taken as soon as possible to be effective.

Emergency hormonal contraception is only effective if taken before you ovulate and will not protect you against pregnancy during the rest of your menstrual cycle.

ellaOne is slightly more effective than Levonelle at preventing pregnancy but it may also prevent other types of hormonal contraception from working for a week after use.

Last updated at: 08 March 2022


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