Progesterone (micronized)
Also called Prometrium; oral micronized progesterone
The same progesterone the ovaries make, in an oral capsule. Prescribed with estrogen to protect the uterus during menopause hormone therapy.
Overview
What it is
A steroid hormone, not a peptide. Prometrium and its generics contain micronized progesterone suspended in peanut oil.
How it works
Estrogen alone makes the uterine lining grow. Progesterone matures and sheds that lining, which prevents the overgrowth that can lead to endometrial cancer. It also has a calming, sleep-promoting effect, which is why it is taken at bedtime.
What the research shows
The PEPI trial showed micronized progesterone protects the uterine lining when combined with estrogen. Label dosing is 200 mg at bedtime for 12 days of each 28-day cycle with estrogen, or 400 mg at bedtime for 10 days to restore periods that have stopped. Many providers also use 100 mg nightly continuously. Observational data suggest it may carry less breast-cancer risk than synthetic progestins, but this has not been confirmed in a large randomized trial.
Studied for
- Protecting the uterus during estrogen therapyFDA approved
- Secondary amenorrhea, periods that have stoppedFDA approved
- Sleep in perimenopausesmall studies
Safety and regulatory status
Safety and side effects
Contains peanut oil: do not use with a peanut allergy. Drowsiness and dizziness are common, so take it at bedtime and do not drive if affected. Labels carry the boxed warnings for estrogen-plus-progestin therapy (blood clots, stroke, heart attack, breast cancer, probable dementia). Not for people with unexplained vaginal bleeding, breast cancer, blood clots or liver disease.
Regulatory status
FDA approved prescription medicine (Prometrium, generics). Requires a prescription.
Common questions
Is this the same as a progestin?
No. Progestins such as medroxyprogesterone are synthetic relatives. Micronized progesterone is the same molecule the body makes.
Why is it taken at night?
It commonly causes drowsiness, so bedtime dosing turns that side effect into a benefit and keeps you safe during the day.