Norgestrel

Key facts

• Norgestrel is a progestin, a synthetic form of progesterone. It is the active ingredient in the over-the-counter daily contraceptive pill sold as Opill, and in some older combined pills taken with oestrogen.
• As a progestin-only pill it is taken at the same time every day, with no placebo week; taking it more than 3 hours late can reduce its effectiveness.
• Any undiagnosed or unexplained vaginal bleeding should be checked by a doctor before starting norgestrel, since the medicine can mask a condition that needs its own treatment.
• Seek urgent care for calf pain and swelling, sudden chest pain or breathlessness, or a severe headache with vision changes, which can signal a blood clot.

What norgestrel treats

Norgestrel is used mainly for contraception. As a progestin-only pill it is suitable for people who want to avoid oestrogen, including while breastfeeding. Older combined formulations paired it with an oestrogen for broader menstrual-cycle control. It is not a treatment for acne or endometriosis, and it does not treat an existing pregnancy.

How norgestrel works

Norgestrel thickens cervical mucus so sperm cannot easily reach an egg, and it thins the lining of the uterus so it is less able to support implantation. At the doses used in progestin-only pills, it does not reliably stop ovulation in everyone, which is why strict daily timing matters.

Before you take it

• Do not take norgestrel if you have current breast cancer, undiagnosed vaginal bleeding, or active liver disease.
• Tell a pharmacist or doctor if you take rifampicin, certain anti-seizure medicines, or St John's wort, as these can lower norgestrel levels and reduce contraceptive protection.
• It does not protect against sexually transmitted infections.
• If you vomit or have severe diarrhoea within a few hours of a dose, treat it as a missed dose and follow backup-contraception instructions.

Side effects

Common effects include irregular spotting, breast tenderness, headache, and mood changes, which often ease after the first few months.

Stop and seek urgent medical care for any of these:

• Leg pain, swelling, or warmth (possible clot).
• Sudden chest pain, breathlessness, or coughing blood.
• Severe headache, sudden vision loss, or slurred speech.
• Severe abdominal pain, which can rarely signal an ectopic pregnancy if the pill fails.

Safety essentials

• Norgestrel carries a small increased risk of venous blood clots; tell your prescriber about smoking, obesity, immobility, or a personal or family history of clots before starting.
• Report any new or unexplained vaginal bleeding rather than assuming it is a normal side effect; it needs a medical review.
• Take every dose at the same time each day. A dose more than 3 hours late needs a backup contraceptive method for the next 2 days, per the product leaflet.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.