Prometrium Is a Bioidentical Progesterone Capsule Used for Hormone Replacement Therapy and Secondary Amenorrhea

If your doctor has mentioned Prometrium — or you've seen it on a prescription label — you probably have questions. What does it do? How do you take it? Is it safe? This guide covers everything you need to know about Prometrium in plain, simple language.

What Is Prometrium?

Prometrium is the brand name for Micronized Progesterone, a prescription medication that contains bioidentical progesterone — meaning it's chemically identical to the progesterone your body naturally makes. It belongs to a class of drugs called progestins.

Prometrium is manufactured by Virtus Pharmaceuticals, LLC. It was FDA-approved for use in the United States and is available as oral capsules in two strengths: 100 mg and 200 mg.

Prometrium is not a controlled substance. A generic version (simply called Progesterone capsules) is also available and widely prescribed.

What Is Prometrium Used For?

Prometrium has two FDA-approved uses:

1. Preventing endometrial hyperplasia — In postmenopausal women who take estrogen (like conjugated estrogens), Prometrium protects the uterine lining from thickening too much, which can lead to cancer. The typical regimen is 200 mg per day for 12 days of each 28-day cycle.
2. Treating secondary amenorrhea — If you've stopped getting your period (and you're not pregnant), Prometrium can help restart it. The usual dose is 400 mg per day for 10 days.

Doctors also prescribe Prometrium off-label for several other conditions:

• Luteal phase support in IVF and fertility treatments
• Prevention of preterm birth in women with a history of early delivery
• Hormone replacement therapy (HRT) as part of combined estrogen-progesterone regimens
• Premenstrual syndrome (PMS) and premenstrual dysphoric disorder (PMDD)
• Irregular uterine bleeding

How Is Prometrium Taken?

Prometrium is taken by mouth, usually at bedtime. Taking it at night helps because one of the most common side effects is drowsiness.

Key dosing details:

• For endometrial protection: 200 mg daily at bedtime for 12 days per 28-day cycle (taken with estrogen)
• For secondary amenorrhea: 400 mg daily at bedtime for 10 days
• Take with food to improve absorption

Important: Prometrium capsules contain peanut oil. If you have a peanut allergy, you cannot take Prometrium. Talk to your doctor about alternatives like Endometrin or compounded Progesterone.

Always take Prometrium exactly as your doctor prescribes. Don't adjust your dose without talking to your provider first.

Who Should Not Take Prometrium?

Prometrium is not safe for everyone. You should not take it if you have:

• Known or suspected breast cancer
• Known or suspected progesterone-dependent tumors
• Undiagnosed abnormal vaginal bleeding
• Active or recent blood clots (deep vein thrombosis or pulmonary embolism)
• Active stroke or heart attack, or history of these conditions
• Liver disease or dysfunction
• Peanut allergy (capsules contain peanut oil)
• Known allergy to Progesterone or any ingredient in Prometrium

Prometrium also carries a boxed warning — the FDA's most serious safety alert. When used with estrogen, it increases the risk of blood clots, stroke, heart attack, breast cancer, and probable dementia in women 65 and older. The FDA advises using it at the lowest effective dose for the shortest time needed.

For more on risks and what to watch for, read our guide to Prometrium side effects.

How Much Does Prometrium Cost?

The cost of Prometrium varies widely depending on whether you get the brand name or generic:

• Brand-name Prometrium: Approximately $1,800 to $1,900 for 90 capsules (100 mg) at full retail price.
• Generic Progesterone capsules: As low as $12 to $50 for a 30-day supply with a discount card. Retail price without a discount is typically $30 to $150 depending on the pharmacy and quantity.

Generic Progesterone capsules are covered by most insurance plans, usually on Tier 1 or Tier 2 formularies. Brand-name Prometrium may require prior authorization or step therapy (trying the generic first).

For tips on getting the best price, check out our guide to saving money on Prometrium.

Final Thoughts

Prometrium is a widely used bioidentical progesterone medication that plays an important role in hormone replacement therapy, menstrual health, and fertility support. It's generally well-tolerated when taken as directed, though it does carry serious risks — especially with long-term use alongside estrogen.

If you've been prescribed Prometrium and are having trouble finding it at your pharmacy, use Medfinder to check stock availability near you. And if you want to understand how Prometrium works in your body, we have a guide for that too.