Progesterone
Micronized progesterone, the body-identical form, taken by mouth with estrogen to keep the uterine lining thin and safe.
FDA-approved (Prometrium, micronized progesterone capsules) to protect the uterine lining during estrogen therapy.
Used for
- Protecting the uterus lining in women taking estrogen
- Sleep: it is sedating, so it is taken at bedtime
- Regulating cycles in perimenopause (under a prescriber)
How it works
Estrogen thickens the uterine lining; progesterone turns that growth off and sheds it. Taken by mouth, it breaks down into calming compounds that act on GABA receptors, which is why it makes you sleepy.
Half-life: about 5–17 hours by mouth
What the research shows
- In the PEPI trial (875 women, 3 years), estrogen alone caused endometrial overgrowth in about a third of women. Adding micronized progesterone, cyclic or continuous, prevented it.
- In the French E3N cohort, estrogen with micronized progesterone carried less breast cancer risk than estrogen with synthetic progestins. This is observational, not a trial.
Dosing
Dosing isn’t listed on the public site. In the app, each published option is shown with its source (a drug label, a clinical guideline, a trial or community reports) and can be turned into a protocol you review.
Work out the units to draw for your vial →Side effects
- Drowsiness, dizziness (take at bedtime)
- Breast tenderness
- Bloating
- Headache
- Spotting or irregular bleeding
Cautions
- Prometrium capsules contain peanut oil: do not use with a peanut allergy.
- Can cause drowsiness and dizziness: take it at bedtime and avoid driving after a dose.
- Not with a history of breast cancer, blood clots or stroke unless a specialist agrees.
- Not a contraceptive at these doses.
Storage
Unmixed or unopened: Capsules at room temperature (25 °C), away from moisture.
From the Prometrium (progesterone) label.
Interactions
Ketoconazole and other CYP3A4 blockers may raise progesterone levels (shown in lab tests; the clinical importance is unknown).
Taken with conjugated estrogens it raised estrone and equilin and lowered estradiol levels in postmenopausal women.
Not a full list. Tell your doctor and pharmacist everything you take.
Reference only, not medical advice. Written for this app from the cited research. Doses marked community-reported are not from trials.