Progesterone Dosage for Endometrial Protection During HRT
For postmenopausal women with a uterus taking estrogen for hot flashes, use oral micronized progesterone 200 mg daily at bedtime for 12-14 consecutive days per 28-day cycle, or continuous combined therapy with 100 mg daily for up to 5 years. 1, 2
Standard Dosing Regimens
The FDA-approved dosing and clinical evidence support two primary approaches:
Sequential (Cyclic) Regimen
- Oral micronized progesterone 200 mg at bedtime for 12-14 days per month when combined with conjugated equine estrogens 0.625 mg 1, 3
- This provides adequate endometrial protection for up to 5 years 2
- The 12-day minimum duration is critical—shorter durations may not provide sufficient protection 4, 3
Continuous Combined Regimen
- Oral micronized progesterone 100 mg daily provides endometrial protection when given continuously for 25 days per month 5
- This regimen induces amenorrhea in over 90% of women by 3-6 months 5
- Better compliance due to reduced bleeding episodes
Critical Dosing Principles
Duration matters more than dose. The Endocrine Society guideline emphasizes that concurrent progestogen therapy for at least 12 days per month reduces endometrial hyperplasia and cancer risk 3. Studies confirm that 12-14 days of sequential therapy is the minimum safe duration 4, 2.
For higher estrogen doses (1.25 mg CEE), consider increasing to 300 mg micronized progesterone for 10 days sequentially 4.
Important Clinical Considerations
Timing and Administration
- Always take at bedtime due to significant drowsiness and dizziness that occurs in many women 1
- Some women experience extreme sedation, blurred vision, difficulty walking, or feeling intoxicated during initial therapy 1
- Take standing with a full glass of water if swallowing difficulty occurs 1
Safety Profile
The WHI data showed continuous combined CEE plus medroxyprogesterone acetate reduced endometrial cancer risk over 13 years 3. However, sequential regimens beyond 5 years may carry a 2-fold increased endometrial cancer risk, particularly in thin women 3. This underscores the importance of regular monitoring.
Peanut Allergy Warning
Progesterone capsules contain peanut oil and are contraindicated in peanut allergy 1.
Alternative Progestogen Options
If micronized progesterone is not tolerated:
- Medroxyprogesterone acetate 5-10 mg for 12-14 days sequentially, or 2.5-5 mg continuously 4
- Levonorgestrel intrauterine device (off-label in US) provides excellent endometrial protection, especially in obese women 3
Monitoring Requirements
- Annual pelvic exam and endometrial assessment
- Any unusual vaginal bleeding requires immediate evaluation 1
- After 5 years of sequential therapy, reassess risk-benefit given potential increased endometrial cancer risk with prolonged use 3, 2
The evidence strongly supports that proper progestogen dosing and duration are non-negotiable for women with a uterus taking estrogen—unopposed estrogen significantly increases endometrial hyperplasia and cancer risk 3.