How it works
Bioidentical means it has the exact same structure as the progesterone your body makes. Micronized means it's ground very fine so it absorbs well. It attaches to progesterone receptors and keeps estrogen from over-thickening the lining of the uterus. Your body breaks it down into allopregnanolone. That boosts the brain's calming GABA-A receptors, which is why it can make you sleepy.
The evidence
PEPI and later trials showed that progesterone protects the lining of the uterus in combined HRT. You can take it in cycles or every day. Both are acceptable. The choice depends on what you prefer and on your symptoms.
Typical dosing
100 mg/day every day, or 200 mg/day in cycles (days 1–14 of each calendar month). Take it at bedtime, so the sleepy effect works for you.
Side effects
Common
- Sleepiness
- Dizziness when you stand up
Less common
- Headache
- Breast tenderness
Drug interactions
- Drugs that change CYP3A4 (a liver enzyme)
- Sedatives: even more drowsiness together
