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Oral Micronized Progesterone Real-World Response Rate: What Patients Actually Experience

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At a glance

  • Drug / progesterone (Prometrium), micronized oral capsules
  • Labeled uses / endometrial protection with conjugated estrogens; secondary amenorrhea [1]
  • Labeled dose / 200 mg at bedtime, 12 days per 28-day cycle [1]
  • Hyperplasia at 36 months / 6% with Prometrium plus estrogen vs 64% with estrogen alone [1]
  • Hot flash score, 300 mg daily / fell 10.0 points vs 4.4 on placebo, 133 women [2]
  • Drowsiness and dizziness / labeled effects; single bedtime dose [1]

Endometrial protection: 6% versus 64%

In the label's 36-month trial, 358 postmenopausal women with a uterus received Prometrium 200 mg for 12 days per 28-day cycle plus conjugated estrogens 0.625 mg, estrogen alone or placebo. Hyperplasia appeared in 6% (7 of 117) on the combination, 64% (74 of 115) on estrogen alone and 3% (3 of 116) on placebo; atypical hyperplasia in 1%, 12% and 0% [1].

PEPI, a 3-year randomized trial of 875 postmenopausal women, biopsied the endometrium in 596. Estrogen alone produced simple hyperplasia in 27.7% versus 0.8% on placebo, complex hyperplasia in 22.7% versus 0.8% and atypical hyperplasia in 11.8% versus 0%; all three estrogen-plus-progestin regimens, including cyclic micronized progesterone 200 mg, had rates similar to placebo (P=.16) [3]. Both trials used conjugated estrogens, not estradiol [1][4].

Hot flashes and sleep

A randomized trial of 133 healthy postmenopausal women aged 44 to 62 found oral micronized progesterone 300 mg at bedtime for 12 weeks lowered the daily hot flash and night sweat score by 10.0 points versus 4.4 on placebo, an adjusted difference of -4.3 (95% CI -6.6 to -1.9); discontinuation with adverse events was 9% (8 on progesterone, 4 on placebo) [2]. In PEPI, every active regimen including estrogen plus cyclic micronized progesterone reduced vasomotor symptoms versus placebo (odds ratios 0.17 to 0.28), with no added benefit from the progestin [5].

For sleep, a small study randomized 21 postmenopausal women to estrogen plus medroxyprogesterone acetate 5 mg (n=11) or estrogen plus oral micronized progesterone 200 mg (n=10), with sleep laboratory recordings at baseline and after 6 months. Sleep efficiency improved 8% (p=0.014) with micronized progesterone and did not improve with medroxyprogesterone acetate [6].

What patients notice

The label says Prometrium may cause transient dizziness and drowsiness and directs a single daily dose at bedtime; during initial therapy a few women had extreme drowsiness, blurred vision, slurred speech, difficulty walking or loss of consciousness [1]. In the 3-year label trial, Prometrium 200 mg plus conjugated estrogens (n=178) versus placebo (n=174) produced breast tenderness 27% vs 6%, headache 31% vs 27%, dizziness 15% vs 9% and depression 19% vs 12%; the active arm also took estrogen, so tenderness and bloating cannot be assigned to progesterone alone [7].

Frequently asked questions

What percentage of people respond to oral micronized progesterone?
Results depend on the endpoint: hyperplasia occurred in 6% of women taking Prometrium 200 mg cyclically with conjugated estrogens over 36 months versus 64% with estrogen alone [1], while a 133-woman hot flash trial found a 10.0-point score drop versus 4.4 on placebo [2].
Does food change absorption?
In 15 postmenopausal women given 200 mg, food raised peak concentration and total exposure without changing time to peak, and absorption was enhanced about twofold [8]. The label states that food increased progesterone bioavailability [7].
Can Prometrium be taken with a peanut allergy?
The label lists peanut allergy as a contraindication because Prometrium capsules contain peanut oil [1].

References

  1. U.S. National Library of Medicine, DailyMed. Prometrium progesterone capsules (Acertis), Rev. 02/2026 prescribing information. Prometrium progesterone capsules (Acertis), Rev. 02/2026 label
  2. Hitchcock CL, Prior JC. Oral micronized progesterone for vasomotor symptoms--a placebo-controlled randomized trial in healthy postmenopausal women. Menopause. 2012;19(8):886-93. Oral micronized progesterone for vasomotor symptoms--a placebo-controlled randomized trial in healthy postmenopausal women
  3. . Effects of hormone replacement therapy on endometrial histology in postmenopausal women. The Postmenopausal Estrogen/Progestin Interventions (PEPI) Trial. The Writing Group for the PEPI Trial. JAMA. 1996;275(5):370-5. Effects of hormone replacement therapy on endometrial histology in postmenopausal women. The Postmenopausal Estrogen/Progestin Interventions (PEPI) Trial. The Writing Group for the PEPI Trial
  4. . Effects of estrogen or estrogen/progestin regimens on heart disease risk factors in postmenopausal women. The Postmenopausal Estrogen/Progestin Interventions (PEPI) Trial. The Writing Group for the PEPI Trial. JAMA. 1995;273(3):199-208. Effects of estrogen or estrogen/progestin regimens on heart disease risk factors in postmenopausal women. The Postmenopausal Estrogen/Progestin Interventions (PEPI) Trial. The Writing Group for the PEPI Trial
  5. Greendale GA, Reboussin BA, Hogan P, Barnabei VM, Shumaker S, Johnson S, et al. Symptom relief and side effects of postmenopausal hormones: results from the Postmenopausal Estrogen/Progestin Interventions Trial. Obstet Gynecol. 1998;92(6):982-8. Symptom relief and side effects of postmenopausal hormones: results from the Postmenopausal Estrogen/Progestin Interventions Trial
  6. Montplaisir J, Lorrain J, Denesle R, Petit D. Sleep in menopause: differential effects of two forms of hormone replacement therapy. Menopause. 2001;8(1):10-6. Sleep in menopause: differential effects of two forms of hormone replacement therapy
  7. U.S. Food and Drug Administration. U.S. Food and Drug Administration
  8. Simon JA, Robinson DE, Andrews MC, Hildebrand JR, Rocci ML, Blake RE, et al. The absorption of oral micronized progesterone: the effect of food, dose proportionality, and comparison with intramuscular progesterone. Fertil Steril. 1993;60(1):26-33. The absorption of oral micronized progesterone: the effect of food, dose proportionality, and comparison with intramuscular progesterone
Evidence overview for Oral Micronized Progesterone Real-World Response Rate: What Patients Actually Experience