How the progestogen only pill works
Unlike the combined pill, which contains copies of the natural hormones oestrogen and progesterone, the progestogen only pill only uses a copy of progesterone.
When you digest the pill, the progestogen gets absorbed into your blood and changes your hormone levels. This affects your body and prevents pregnancy in 3 ways:
it thickens the mucus in the cervix to stop sperm from getting into the womb
it stops ovulation in 60-97% of people, depending on which type you take
it thins the lining of the womb, so a fertilised egg can’t stay in place – this is a back-up measure as the eggs aren’t likely to be fertilised in the first place if you’re taking this pill
What happens to the progestogen only pill in your body?
The pill is digested in your stomach.
Your bloodstream takes the ingredients of the pill all over your body, changing your hormone levels and leading to other health benefits, risks and side effects.
Your liver changes the hormones from the pill so they’re ready to be expelled from your body.
Hormones are lost from your body through your bowel – so you have to keep taking them every day to keep hormones at the levels that prevent pregnancy.
What type of pill should you take?
There are 3 types of progestogen only pill to choose from, and they all work the same way. But they use different types of progestogen.
They also have different timing windows for taking your pill each day, before it’s considered missing a pill. For traditional progestogen only pills, you must take them within 3 hours of your usual time. For newer types, you have longer to remember.
Pills that contain desogestrel
Pros: it’s over 99% effective. It’s more likely to stop ovulation and you have 12 hours to remember to take it before it counts as a missed pill.
Brand names:
Cerelle
Cerazette
Zelleta
Feanolla
Pills that contain levonorgestrel or norethisterone
Pros: it’s highly effective at preventing pregnancy at 98.5%.
Cons: it’s less likely to stop ovulation and you only have a 3-hour window to remember to take it before it counts as a missed pill.
Brand names:
Norgeston
Noriday
Pills that contain drospirenone
Pros: it’s 99% effective and you have 24 hours to remember to take each pill.
Cons: only available through the NHS if you cannot take desogestrel
Brand names:
Slynd
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