The progestogen-only pill (mini pill): timing windows, side effects and who can take it

The progestogen-only pill is a hormonal contraceptive containing progestogen, which mimics the effects of progesterone. It prevents pregnancy by stopping the ovaries releasing an egg each month. Types mentioned by the NHS are the traditional pill, desogestrel and drospirenone.

Because it contains no oestrogen, it can suit people who cannot tolerate it, as well as those who have recently given birth or who are breastfeeding. It may also help with painful or heavy periods and endometriosis.

Take one pill at around the same time every day, with no break between 28-pill packs. How late is too late depends on the pill type.

Starting on days 1 to 5 of your cycle gives immediate protection with traditional and desogestrel pills. For drospirenone only day 1 gives immediate protection. If you start later, use condoms for 2 days with traditional or desogestrel pills, or 7 days with drospirenone.

After a birth, starting within 20 days gives immediate protection; from 21 days, extra contraception is needed for 2 to 7 days depending on the type.

The NHS says the pill is not suitable if you have ever had a heart or blood vessel condition (cardiovascular disease), a stroke, a liver condition such as cirrhosis, breast cancer or a kidney condition. Talk to a doctor, nurse or pharmacist if any of these apply.

Some medicines can interfere with it. The NHS asks you to check before use if you take medicines for TB, epilepsy or HIV, the antifungal griseofulvin, lamotrigine, or the herbal remedy St John's wort.

The NHS says it has few side effects. The most notable are changes to periods, which may be lighter, more frequent or may stop, with spotting between cycles. Acne, mood changes, weight gain or altered sex drive are sometimes reported, but there is not enough evidence to say they are caused by the pill.

Fluid-filled sacs can form on the ovaries; they are not dangerous, usually do not need removing and often disappear without treatment, though they can occasionally cause pelvic pain. There may be a possible link with breast cancer, but the evidence is limited and any increase is very small.

The pill may not work if you vomit within 2 hours of a traditional pill, or within 3 to 4 hours of a desogestrel or drospirenone pill, or if you have severe watery diarrhoea. Contact a pharmacist, sexual health clinic, GP or NHS 111, and ask about emergency contraception.

For late or missed pills, the right action depends on how long it has been and the type of pill; the pack leaflet and a pharmacist can advise. The progestogen-only pill can affect how some emergency contraception works. An extra pill is unlikely to cause harm, though it may cause nausea, vomiting or vaginal bleeding.

The progestogen-only pill does not stop you getting or passing on sexually transmitted infections, so condoms are recommended for that. When you stop it, it usually takes about 1 month for your chance of getting pregnant to return to what it was before.