Skip to content
ClinCalc Pro
Menu
Calculators Drugs Pathways AI Dx Donate Get the App
Natural progestogen (micronised) Pregnancy: SPC §4.6: if pregnancy occurs during medication the capsules should be withdrawn immediately. Data on a large number of exposed pregnancies indicate no adverse effects of progesterone on the foetus, and most epidemiological studies of inadvertent foetal exposure to estrogen + progesterone combinations indicate no teratogenic or foetotoxic effect. Prescription beyond the first trimester may reveal gravidic cholestasis. Not indicated during breast-feeding (contraindicated, §4.3); progesterone is distributed into breast milk.

Progesterone

Brand names: Cyclogest, Crinone, Utrogestan, Lutigest

Progesterone is the natural progestogen, used for luteal-phase and early-pregnancy support in assisted reproduction, as the progestogen component of menopausal hormone therapy, and to reduce preterm birth risk in selected women.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 200 mg daily at bedtime for twelve days in the last half of each therapeutic cycle (beginning on Day 15 and ending on Day 26)
Route: Oral — capsules should NOT be taken with food (concomitant food increases the bioavailability of micronised progesterone) and should be taken at bedtime
Frequency: Once daily at bedtime, for 12 days of each therapeutic cycle
INDICATION (eMC §4.2): opposing the increased risk of endometrial cancer in women receiving estrogen replacement therapy. ALTERNATIVE REGIMEN verbatim: 'Alternatively 100 mg can be given at bedtime from Day 1 to Day 25 of each therapeutic cycle, withdrawal bleeding being less with this treatment schedule.' Withdrawal bleeding may occur in the week following the 200 mg × 12-day regimen. For initiation and continuation of treatment of postmenopausal symptoms the lowest effective dose for the shortest duration should be used. PAEDIATRIC: 'There is no relevant use of Progesterone in the paediatric population.' ELDERLY: 'As for adults.' The fetched SPC is for the ORAL 100 mg soft capsule and contains no vaginal posology — see the separate progesterone_vaginal entry. US labelling cross-check only (openFDA, PROGESTERONE capsules, Bryant Ranch Prepack, 2025-05-16 — US labelling may differ from UK): prevention of endometrial hyperplasia 200 mg orally at bedtime for 12 days sequentially per 28-day cycle; treatment of secondary amenorrhoea 400 mg at bedtime for 10 days.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • Known hypersensitivity to the active substances, soybean lecithin, peanut or to any of the excipients
  • Known, past or suspected breast cancer
  • Known or suspected estrogen-dependent malignant tumours (e.g. genital tract carcinoma)
  • Undiagnosed genital bleeding
  • Previous or current thromboembolic disorders (e.g. deep venous thrombosis, pulmonary embolism) or thrombophlebitis
  • Known thrombophilic disorders
  • Acute liver disease, or a history of liver disease as long as liver function tests have failed to return to normal
  • Porphyria
  • Cerebral haemorrhage
  • Breast-feeding
  • Not suitable in confirmed pregnancy, in the treatment of premature labour, or as a contraceptive (SPC §4.4)

Side effects

  • Headache (31% in the PEPI trial with conjugated estrogens 0.625 mg vs 27% placebo); migraine also reported post-marketing
  • Breast tenderness (27% vs 6% placebo)
  • Depression (19% vs 12% placebo)
  • Dizziness (15% vs 9% placebo) and somnolence — may occur 1 to 3 hours after intake; bedtime dosing and dose reduction may reduce these effects
  • Abdominal bloating (12%), abdominal pain and nausea
  • Vaginal discharge / vaginal haemorrhage; pruritus; fatigue

Clinical monograph

How it works

It acts on progesterone receptors to transform oestrogen-primed endometrium into a secretory state, support implantation and pregnancy maintenance, and oppose oestrogenic endometrial proliferation.

Prescribing in practice

  • When used to oppose oestrogen in women with an intact uterus, adequate progestogen exposure is essential to protect against endometrial hyperplasia and carcinoma.
  • Undiagnosed vaginal bleeding must be investigated before use, and it is contraindicated in active thromboembolic disorders.
  • Oral micronised progesterone commonly causes drowsiness and is usually taken at bedtime.

Monitoring

No routine blood monitoring is required; investigate any unexpected vaginal bleeding and review the indication periodically.

Counselling the patient

  • Take oral capsules at bedtime as they can cause drowsiness.
  • Use vaginal preparations exactly as directed for fertility or pregnancy support.
  • Report any unexpected vaginal bleeding.

Evidence & guidelines

Vaginal progesterone for prevention of preterm birth in women with a short cervix is supported by NICE guidance and randomised trial evidence.

Reference: NICE NG23/NG126; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

Calculators
Pathways