Yes, Xiromed progesterone is bioidentical. Its active ingredient is micronized progesterone, which is chemically identical to the progesterone your ovaries naturally produce. It comes in 100 mg and 200 mg oral capsules and is a generic version of the brand-name drug Prometrium.
What Makes It Bioidentical
The term “bioidentical” means the hormone in the medication has the exact same chemical structure as the hormone your body makes on its own. Xiromed progesterone meets this definition. Its FDA labeling explicitly states that it is “chemically identical to progesterone of ovarian origin.”
This is different from synthetic progestins like medroxyprogesterone acetate (the active ingredient in Provera) or norethindrone. Those drugs mimic some of progesterone’s effects, but their molecular structure is altered. Because bioidentical progesterone is a structural match, it binds to the same receptors in the same way your body’s own progesterone does.
How It’s Made
Even though Xiromed progesterone is called “bioidentical” or sometimes “natural,” it doesn’t come straight from a plant and into the capsule. The progesterone is synthesized from plant-based starting materials, typically compounds extracted from wild yam or soy. Those raw materials are then processed in a pharmaceutical lab until the final molecule is an exact copy of human progesterone. The end product carries the USP (United States Pharmacopeia) designation, meaning it meets strict purity and potency standards.
“Micronized” refers to the manufacturing process that grinds the progesterone into very small particles. This improves absorption in the gut, since progesterone on its own is poorly absorbed when taken by mouth.
Xiromed vs. Prometrium
Prometrium was the first FDA-approved oral micronized progesterone capsule. Xiromed’s version is a generic equivalent, meaning it contains the same active ingredient at the same dose in the same form. The FDA requires generic drugs to demonstrate bioequivalence to the brand-name product before approval, so your body absorbs and uses them in essentially the same way.
Where generics can differ is in their inactive ingredients: the oils, dyes, and fillers that make up the rest of the capsule. Prometrium, for example, uses peanut oil as a carrier. If you have a peanut allergy, the specific inactive ingredients in any progesterone capsule matter. Check the product labeling or ask your pharmacist about the carrier oil in Xiromed’s formulation, especially if you have food sensitivities.
How It Differs From Compounded Progesterone
Some pharmacies offer custom-compounded bioidentical progesterone, which is also made from plant-derived progesterone. The key difference is regulatory oversight. Xiromed’s capsules are FDA-approved, meaning their potency, purity, and consistency are verified through standardized manufacturing and testing. Compounded hormones are mixed by individual pharmacies and are not subject to the same FDA review process. Studies have found that compounded hormone products can vary in the actual dose delivered from one batch to the next.
Both contain the same molecule. The distinction is in quality control and the evidence base behind the specific product. FDA-approved versions like Xiromed progesterone and Prometrium have gone through clinical trials to establish their safety and efficacy for specific uses, such as preventing uterine lining overgrowth in postmenopausal women taking estrogen and treating certain cases of absent menstrual periods.
Bioidentical vs. Synthetic: Why It Matters
The bioidentical vs. synthetic distinction matters most when it comes to side effects and how the hormone is processed in your body. Micronized progesterone is metabolized into the same byproducts your body creates naturally, some of which have a mild calming effect (which is why progesterone capsules can cause drowsiness and are often taken at bedtime). Synthetic progestins follow different metabolic pathways and carry a somewhat different side effect profile.
Large observational studies have suggested that bioidentical progesterone may carry a lower risk of blood clots and breast-related concerns compared to certain synthetic progestins, though the evidence is still being refined. Both types effectively protect the uterine lining when paired with estrogen therapy, which is their primary clinical purpose in menopause treatment.
If your pharmacy fills your progesterone prescription with Xiromed’s product, you are getting an FDA-approved, bioidentical hormone that is molecularly the same as what your body produces and therapeutically equivalent to Prometrium.