Hi CM213, I take Prometrium capsules (prescribed to me by my HRT doctor).
CLINICAL PHARMACOLOGY
PROMETRIUM Capsules are an oral dosage form of micronized progesterone which is
chemically identical to progesterone of ovarian origin. The oral bioavailability of
progesterone is increased through micronization.
(quoted by the manufacturer)
All progesterone starts from a plant source, mostly using wild yam. Micronizing makes the plant source become bioidentical progesterone (USP).
I take one capsule orally because during liver metabolism the progesterone capsule further breaks down into ketosis, which helps with overnight weight loss (from my experience). Additionally, I'll use two more capsules (for a total of 300 mg). I'll either decide to take them rectally or spread each capsule (after poking a hole in it) on my breasts.
Some get pharma strength progesterone from in-house pharmacy (or the like)... when it's available. I think just starting off using PC (like the one you listed) first is okay. Although the one you listed has too many ingredients. I saw an organic PC available, and it looks like all the ingredients used are organic. In the past I started with Smoky Mountain PC (aka SMNutrition) and had good success with.