Executive summary (what clinicians actually need)
- Do before first issue: BP, BMI, smoking status, migraine history (especially aura), VTE/personal & family history, postpartum/breastfeeding status, relevant meds (enzyme inducers).
- Absolute “stop/avoid” themes: migraine with aura, very high VTE risk, uncontrolled hypertension, major thrombophilia, current breast cancer, severe liver disease (apply UKMEC locally).
- Missed pills: risk is primarily when pills are missed around the hormone-free interval. Use the 48-hour rule to decide if additional precautions/EC are needed.
- Snip-worthy rule: <48h late → take ASAP, continue, no extra contraception. ≥48h (≥2 pills missed) → take last missed pill ASAP + condoms 7 days + consider EC depending on week.
Starting CHC (quick rules)
- Day 1 start: immediate contraceptive cover.
- Day 2–5 start: cover is immediate for most COCs; if uncertain, advise condoms for 7 days (local/FSRH nuance varies by regimen).
- After day 5 (“quick start”): can start today if reasonably excludes pregnancy + condoms 7 days + arrange pregnancy test in 3 weeks if any risk.
- Switching from POP/implant/injection: typically overlap/backup 7 days if not switching exactly at correct timepoint.
High-risk history that changes everything
Specifically ask about migraine aura, prior VTE/PE, strong first-degree family VTE <50y, thrombophilia, smoking age >35, and current uncontrolled hypertension. If present, CHC may be contraindicated or require specialist advice (UKMEC).
Missed pills: the “48-hour rule” (featured snippet format)
- If <48 hours late (1 pill missed): take the missed pill ASAP (even if this means 2 in one day), continue pack. No extra contraception needed.
- If ≥48 hours late (2+ pills missed):
- Take the last missed pill ASAP (discard earlier missed pills).
- Continue the rest of the pack as normal.
- Use condoms for 7 days.
- Week 1 miss + UPSI in last 7 days: consider emergency contraception.
- Week 3 miss: omit the hormone-free interval (finish active pills and start next pack immediately).
- Vomiting/diarrhoea: treat as missed pills depending on timing and duration.
VTE counselling (short, documentable)
- Explain CHC slightly increases VTE risk versus baseline; absolute risk remains low for many, but rises with age, BMI, smoking, postpartum, immobility, thrombophilia.
- Safety-net symptoms: unilateral leg swelling/pain, sudden pleuritic chest pain, breathlessness, haemoptysis, collapse → urgent assessment.
- Consider LARC if adherence is likely to be poor or risk factors accrue.
Frequently asked questions
Do I need routine blood tests before CHC?
Not routinely. The essentials are BP, BMI, migraine/VTE risk, and medication review. Consider targeted tests if history suggests (e.g., lipids/diabetes risk) but CHC prescribing is mainly clinical risk stratification.
When is EC needed after missed pills?
Highest risk is missed pills in Week 1 (right after the hormone-free interval) with unprotected sex in the previous 7 days. Week 3 misses are managed by skipping the hormone-free interval to prevent ovulation.
What is the most common real-world failure mode?
Poor adherence around the hormone-free interval. Offering tailored regimens or switching to LARC often improves “typical use” effectiveness.
Transparency
This page is an educational, clinician-written summary of publicly available NICE guidance intended for trained healthcare professionals. It uses original wording (not copied text) and should be used alongside the full NICE source, local pathways, and clinical judgement. Doses provided are for general reference; always check the BNF/SPC.