01Purpose and principlesWhat the treatment does and how it fits into care.
CHC suppresses ovulation through combined oestrogen and progestogen effects and also thickens cervical mucus and alters endometrium. It provides effective reversible contraception with cycle control and benefits for dysmenorrhoea, heavy bleeding, acne and selected endocrine symptoms. These benefits are considered only after medical eligibility because oestrogen increases venous and arterial thrombotic risk in susceptible people.
The safest first-line combined pill for many eligible users contains no more than 30 micrograms ethinylestradiol with levonorgestrel or norethisterone because this balances control with lower VTE risk than some other formulations. Individual preference, previous adverse effects and non-oral absorption needs can justify alternatives. Patch and ring simplify use for some people but remain CHC for UKMEC purposes.
Traditional 21/7 use is one option, not a biological necessity. Shortened hormone-free intervals, extended use and continuous regimens can reduce withdrawal symptoms and theoretical escape ovulation when used with suitable monophasic products. Missed-dose action depends on where the error falls relative to a hormone-free interval and on recent unprotected sex; use the current product and CoSRH missed-use algorithm.
Key points
- CHC includes combined oral pills, transdermal patches and vaginal rings; changing route does not avoid oestrogen-related VTE, stroke or migraine-aura restrictions.
- Current migraine with aura is UKMEC 4; aura at least five years in the past is category 3. Smoking from age 35 is category 3 below 15 cigarettes daily and category 4 at 15 or more.
- Adequately controlled hypertension or blood pressure 140–159/90–99 mmHg is UKMEC 3 for CHC; blood pressure at least 160 systolic or 100 diastolic, or vascular disease, is category 4.
- During breastfeeding, CHC is category 4 from birth to under six weeks, category 2 from six weeks to under six months when primarily breastfeeding, and category 1 from six months on that factor alone.
- When not breastfeeding, CHC before three weeks postpartum is category 4 with additional VTE risk and category 3 without it; at three to under six weeks it is category 3 with VTE risk and category 2 without; from six weeks it is category 1 on postpartum timing alone.
- A monophasic combined pill can use standard or tailored regimens with fewer or no hormone-free intervals; there is no health requirement for monthly withdrawal bleeding.
- Liver enzyme-inducing medicines reduce pill, patch and ring efficacy. Oestrogen also reduces lamotrigine exposure; use specialist interaction advice and an unaffected contraceptive method where appropriate.
- Check blood pressure and relevant history before supply, explain common bleeding or hormone-free-interval effects, and review at least annually or sooner after any new diagnosis or medicine.
02Indications, selection and cautionsWho may benefit, who needs urgent treatment and important alternatives.
Unilateral swelling or pain, unexplained breathlessness, pleuritic pain, haemoptysis or collapse suggests DVT or pulmonary embolism.
Focal deficit, speech or visual disturbance, severe sudden headache or cardiac chest pain requires emergency assessment.
Fully reversible focal visual, sensory or speech symptoms preceding headache differ from nonspecific blur and change CHC eligibility.
Headache, mood change, bleeding and pelvic pain clustering during the break may improve with a shortened or omitted interval.
Enzyme induction, vomiting, severe diarrhoea or missed use near a hormone-free interval can permit ovulation and trigger emergency-contraception assessment.
03Assessment before treatmentTests and checks that guide safe selection.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Accurate blood pressureFirst step - Why
- Identify category 3 or 4 hypertension before initiation and during continuing use.
- Interpretation and limitations
- Use repeated properly obtained readings for stable classification, while severe symptomatic hypertension requires urgent action.
- 02
Focused vascular and migraine history - Why
- Identify VTE, thrombophilia, smoking, arterial disease and aura that alter eligibility.
- Interpretation and limitations
- A normal thrombophilia screen does not cancel a personal VTE history, and routine thrombophilia testing is not required for everyone.
- 03
BMI and combined risk assessment - Why
- Identify obesity and interacting VTE factors that may shift the risk-benefit balance.
- Interpretation and limitations
- UKMEC categories apply to defined characteristics; several category-2 factors acting through VTE merit cautious combined assessment.
- 04
Pregnancy timing assessment - Why
- Exclude established pregnancy reasonably and decide whether emergency contraception or backup is needed.
- Interpretation and limitations
- An early negative urine test does not exclude conception from recent sex; date the follow-up test from the latest risk.
- 05
Medicine interaction check - Why
- Detect enzyme induction, lamotrigine interaction and medicines whose fetal risk makes highly effective contraception important.
- Interpretation and limitations
- Assess both directions of interaction; simply increasing the pill dose is not a universal safe solution.
04Treatment approachPreparation, options, escalation and aftercare.
01Initiation pathwayConfirm CHC suitability and chosen regimenFirst stepAn eligible person requests a combined pill, patch or ring.+
- 1Check blood pressure, smoking, migraine aura, BMI, VTE and arterial history, postpartum or breastfeeding status, liver and breast disease and current medicines.
- 2Discuss effectiveness, LARC alternatives, VTE risk, bleeding, hormone-free symptoms and whether standard, shortened, extended or continuous use best fits the selected formulation.
- 3Provide written starting, backup and missed-use instructions, an adequate supply, urgent warning symptoms and a planned review.
02New-risk pathwayStop and reassess when eligibility changesA CHC user develops aura, severe hypertension, VTE symptoms, major immobilisation or a new interacting medicine.+
- 1Withhold further CHC and assess the possible emergency or new UKMEC characteristic promptly.
- 2Maintain pregnancy prevention with an eligible non-oestrogen bridge or emergency contraception where needed.
- 3Document the changed category and interaction, then arrange longer-term contraception after the acute issue is addressed.
03Missed-use pathwayProtect the next ovulation windowPills, patch or ring have been missed, detached, delayed or restarted late.+
- 1Identify the exact formulation, number of missed active doses, timing relative to the hormone-free interval and recent unprotected sex.
- 2Follow the current method-specific algorithm for immediate replacement, continued use and duration of additional precautions.
- 3Assess emergency contraception when the error could extend the hormone-free interval, and remember that ulipristal requires a delay before restarting hormones.
05Regimens, contraindications and interactionsTreatment details and the circumstances that modify them.
Ethinylestradiol with levonorgestrel combined pill
Take one active tablet daily using the licensed schedule or a supported tailored regimen with shortened, less frequent or no hormone-free interval for a monophasic preparation.Confirm the exact strength and product; avoid in UKMEC 4 conditions, review category 3 risks, smoking, blood pressure, migraine aura and interacting medicines.
Combined transdermal patch or vaginal ring
Apply or insert on the product-specific weekly or three-week schedule, replacing a detached patch or delayed ring according to its missed-use instructions.Non-oral use does not remove vascular contraindications or enzyme-inducer interactions; confirm adhesion, expulsion, storage and backup rules.
06Complications, monitoring and follow-upAdverse effects, response and longer-term review.
- Recheck medical eligibility, blood pressure, smoking, migraine symptoms, medicines, adherence and satisfaction at least annually.
- Review sooner for new headache phenotype, aura, leg or chest symptoms, hypertension, surgery, immobility, postpartum change or a new interacting drug.
- Ask whether bleeding or hormone-free symptoms are acceptable and offer a tailored monophasic regimen when appropriate.
- After any missed-use episode, document exact timing, emergency-contraception assessment, backup duration and the planned pregnancy test.
- Support smoking cessation and alternative contraception without withholding care or assuming age alone determines every vascular risk.
07Special situationsVariants, exceptions and circumstances that change the usual approach.
Patch and ring remain CHC
They bypass daily oral dosing but still contain oestrogen and retain CHC medical eligibility and enzyme-induction concerns.
Withdrawal bleeding is optional
A monthly bleed has no health benefit; suitable monophasic pills can be used with shorter or absent breaks.
Aura needs precise history
Transient focal neurological symptoms are different from nonspecific headache or blurred vision and move CHC to category 4.
Postpartum categories change quickly
Breastfeeding and VTE factors create different category transitions before three weeks, at six weeks and at six months.
Interactions can be bidirectional
An inducer can lower contraceptive hormones, while CHC can lower lamotrigine concentrations and affect seizure control.
08Common pitfallsFrequent interpretation and management errors.
- 01
Switching from combined pill to patch after migraine aura and calling it non-oestrogen.
- 02
Using CHC during the first six breastfeeding weeks.
- 03
Treating monthly withdrawal bleeding as medically necessary.
- 04
Failing to assess emergency contraception after a prolonged hormone-free interval.
- 05
Renewing CHC without blood pressure, migraine and medicine review.