Quick answer
What is contraceptive pill used for?
The contraceptive pill is a reliable form of hormonal contraception when taken correctly. The combined pill contains oestrogen and progestogen; the progestogen-only (mini) pill contains only progestogen. Both prevent pregnancy and can regulate periods and reduce period pain. A GP or contraception clinic helps you choose the right type.
How the contraceptive pill works
The contraceptive pill is one of the most widely used forms of hormonal contraception in the UK. There are two main types:
Combined oral contraceptive pill (COCP) — contains oestrogen and progestogen. Stops ovulation, thickens cervical mucus (blocking sperm), and thins the womb lining.
Progestogen-only pill (POP / mini pill) — contains progestogen only. Mainly works by thickening cervical mucus and thinning the womb lining. Some types also stop ovulation.
Both are highly effective when taken correctly.
Effectiveness
With perfect use — taken correctly every day — the pill is over 99% effective.
With typical use — including occasional missed pills — effectiveness is around 91%. Missing pills, vomiting, and some medicines (including some antibiotics and anti-epilepsy drugs) reduce effectiveness.
The pill does not protect against STIs — use condoms for infection protection.
Starting the pill
A GP, nurse, or contraception clinic will:
- check blood pressure and BMI
- ask about medical history — migraines, clots, smoking
- explain how to take your specific pill
- advise when contraceptive protection begins
You can often start immediately if sure you are not pregnant, or on the first day of your next period.
Combined pill — how to take it
21-day packs — take one pill daily for 21 days, then stop for 7 days (withdrawal bleed usually occurs). Start next pack after 7 days.
Everyday (ED) packs — 21 active pills and 7 inactive pills. Take one daily without a break.
Continuous or extended use — some people run packs together to reduce or skip periods — discuss with a GP.
Mini pill — how to take it
Take one pill at the same time every day, without a break.
Traditional POP — must be within 3 hours of the usual time.
Desogestrel POP (Cerazette and generics) — 12-hour window.
Missing the window reduces effectiveness — use condoms for 48 hours after a late pill.
Benefits beyond contraception
The pill can also:
- regulate periods and reduce period pain
- lighten heavy periods
- improve acne and excess hair (combined pill)
- reduce ovarian and womb cancer risk with long-term use
- help manage PCOS symptoms
Side effects
Common when starting — usually settling within 2 to 3 months:
- nausea (take with food or at bedtime)
- breast tenderness
- headaches
- spotting between periods
- mood changes
If side effects persist, switching pill type or formulation often helps.
Risks of the combined pill
The combined pill slightly increases risk of:
- blood clots (DVT and pulmonary embolism) — rare but serious
- stroke and heart attack — very rare in healthy young women
- breast and cervical cancer — small increased risk while taking; breast cancer risk returns to normal after stopping
Benefits and risks are assessed individually. The pill is not suitable for everyone — smokers over 35, migraine with aura, history of clots, and certain medical conditions exclude combined pill use. The mini pill may be an alternative.
Missing pills
Missed pill advice depends on the specific pill, how many are missed, and timing in the pack. Always check the patient information leaflet or use the NHS missed pill guidance.
General principles:
- take the missed pill as soon as remembered
- continue the pack
- use condoms for 7 days (combined pill) if pills were missed
- emergency contraception may be needed if unprotected sex occurred — ask a pharmacist or GP
Stopping the pill
Fertility usually returns quickly — ovulation can occur within weeks. Periods may take 1 to 3 months to regulate. The pill does not cause long-term infertility.
See a GP when planning pregnancy — folic acid supplementation is recommended before conception.
Other contraception options
If the pill does not suit you, alternatives include:
- contraceptive implant, injection, or patch
- hormonal IUD (Mirena) or copper IUD
- barrier methods — condoms, diaphragm
- natural methods — less reliable
A contraception clinic helps you find the best fit for your lifestyle and health.
When to seek urgent help on the pill
While taking the combined pill, seek urgent medical help for:
- sudden severe chest pain or breathlessness
- painful swollen leg
- severe headache with vision disturbance
- weakness or numbness on one side
These may indicate a blood clot or stroke — rare but treatable if caught early.
Common questions
- What is the difference between combined and mini pill?
- The combined pill (COCP) contains oestrogen and progestogen — stops ovulation, thickens cervical mucus. The progestogen-only pill (POP/mini pill) contains only progestogen — mainly thickens mucus and thins the womb lining; must be taken at a consistent time daily.
- How effective is the contraceptive pill?
- Over 99% effective with perfect use. Typical use — allowing for missed pills — is about 91% effective. Effectiveness depends on taking it correctly every day.
- What are common side effects when starting?
- Nausea, breast tenderness, headaches, and spotting between periods often settle within 2 to 3 months. Switching pill type may help if side effects persist. The pill does not cause infertility — fertility returns quickly after stopping.
- Who should not take the combined pill?
- Women over 35 who smoke, history of blood clots, stroke, migraine with aura, certain heart conditions, breast cancer, or liver disease. The progestogen-only pill may be suitable when combined pill is not. A GP assesses individual risk.
- What if I miss a pill?
- Depends on which pill, how many missed, and where in the pack. Take the missed pill as soon as remembered and continue the pack. Use extra contraception (condoms) for 7 days if you miss combined pills, or 48 hours for some mini pills. Check the patient leaflet or ask a pharmacist/GP — do not guess.