What Is Prometrium?

Prometrium is a brand-name prescription medication containing micronized progesterone, a bioidentical form of the hormone progesterone that is chemically identical to what the body naturally produces. It is manufactured by Virtus Pharmaceuticals, LLC.

Prometrium is FDA-approved for two primary uses:

• Prevention of endometrial hyperplasia in postmenopausal women receiving conjugated estrogens
• Treatment of secondary amenorrhea (absence of menstrual periods)

It is also widely used off-label for luteal phase support in IVF and fertility treatments, prevention of preterm birth, hormone replacement therapy (HRT), and management of premenstrual syndrome (PMS).

Important: Prometrium capsules contain peanut oil and are contraindicated in patients with peanut allergies.

How does Prometrium work?

Prometrium contains micronized progesterone, which binds to progesterone receptors in the uterine lining (endometrium). This transforms a proliferative endometrium into a secretory one, which protects against endometrial hyperplasia caused by unopposed estrogen therapy.

Progesterone also plays a critical role in maintaining pregnancy and regulating the menstrual cycle. The micronized formulation improves oral bioavailability compared to non-micronized progesterone. Taking Prometrium with food further increases absorption.

Prometrium is typically taken at bedtime because it commonly causes drowsiness and dizziness.

What doses are available for Prometrium?

• 100 mg oral capsule — available in both brand-name Prometrium and generic Progesterone
• 200 mg oral capsule — available in both brand-name Prometrium and generic Progesterone

Typical dosing ranges from 100 mg to 400 mg daily depending on the indication. For endometrial protection, the standard dose is 200 mg daily at bedtime for 12 days per 28-day cycle. For secondary amenorrhea, 400 mg daily at bedtime for 10 days.

How hard is it to find Prometrium in stock?

Prometrium and its generic equivalent, Progesterone capsules, have been experiencing intermittent shortages since late 2023. As of October 2025, ASHP listed Progesterone capsules — including both brand-name Prometrium and generic versions from Amneal Pharmaceuticals — as being in shortage. The shortages are driven by increased demand from off-label fertility and hormone replacement therapy (HRT) use, manufacturing delays, and a limited number of generic manufacturers.

With a findability score of 60 out of 100, Prometrium can be difficult to locate at times, particularly the generic formulation. You may need to call multiple pharmacies or use tools like Medfinder to check stock availability near you. Brand-name Prometrium may be slightly easier to find but comes at a significantly higher price point.

Who Can Prescribe Prometrium?

Several types of healthcare providers commonly prescribe Prometrium:

• Obstetricians and Gynecologists (OB/GYN) — the most common prescribers, for menstrual disorders, HRT, and pregnancy support
• Reproductive Endocrinologists — for fertility treatments and luteal phase support during IVF
• Endocrinologists — for hormonal imbalances
• Primary Care Physicians and Family Medicine doctors — for HRT and amenorrhea
• Internal Medicine physicians — for hormone-related conditions

Telehealth providers can also prescribe Prometrium, making it accessible even if you don't have a local specialist.

Is Prometrium a controlled substance?

No, Prometrium is not a controlled substance. It is not scheduled by the DEA. This means it can be prescribed without the additional restrictions that apply to controlled medications, and refills are generally straightforward. Prometrium can also be prescribed via telehealth visits.

Common Side Effects of Prometrium

The most frequently reported side effects of Prometrium include:

• Headache (reported in up to 31% of patients)
• Drowsiness/somnolence (27%) — this is why it's taken at bedtime
• Dizziness (24%)
• Breast tenderness
• Abdominal pain and bloating
• Nausea
• Mood changes and irritability
• Vaginal discharge or spotting
• Joint pain
• Fatigue

Serious side effects are rare but can include blood clots, stroke, heart attack, and severe allergic reactions. Contact your doctor immediately if you experience chest pain, sudden severe headache, vision changes, or leg swelling.

Alternative Medications to Prometrium

If you cannot find Prometrium in stock or are looking for other options, these alternatives may be worth discussing with your doctor:

• Medroxyprogesterone (Provera) — a synthetic progestin used for endometrial protection and amenorrhea. Less expensive than Prometrium but not bioidentical.
• Norethindrone Acetate (Aygestin) — a synthetic progestin used for endometriosis, amenorrhea, and abnormal uterine bleeding.
• Endometrin (vaginal Progesterone insert) — a vaginal Progesterone insert used primarily for luteal phase support in fertility treatments. Delivers Progesterone locally with fewer systemic side effects.
• Compounded Progesterone — custom-compounded bioidentical Progesterone available from compounding pharmacies. Not FDA-approved but used when commercial products are unavailable.

Drug Interactions with Prometrium

Prometrium can interact with several medications. Tell your doctor about all drugs and supplements you take:

• Ketoconazole and other strong CYP3A4 inhibitors — can increase Progesterone levels in your body
• St. John's Wort — a CYP3A4 inducer that may decrease Progesterone levels and reduce efficacy
• Rifampin — may significantly reduce Prometrium's effectiveness
• Carbamazepine, Phenytoin, Phenobarbital — anticonvulsants that can decrease Progesterone levels
• Grapefruit juice — may increase Progesterone levels through CYP3A4 inhibition

Prometrium is often intentionally combined with conjugated estrogens as part of hormone replacement therapy — this is a therapeutic combination, not a harmful interaction.

Final Thoughts on Prometrium

Prometrium is an important bioidentical Progesterone medication used by thousands of women for hormone replacement, menstrual disorders, and fertility support. While the ongoing shortage of Progesterone capsules — affecting both brand-name Prometrium and generic versions — can make finding this medication frustrating, it is still possible to locate with some persistence.

Generic Progesterone capsules are very affordable with discount cards ($12 to $50 for a 30-day supply), and most insurance plans cover them on lower formulary tiers. If you're having trouble finding Prometrium in stock, try using Medfinder to check pharmacy availability near you, ask your pharmacist about expected restock dates, or discuss alternative Progesterone formulations with your doctor.