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Prescription medication — not a dietary supplement
Progesteroneis a prescription (or investigational) drug, not a supplement. It is included here for reference because people research and discuss it (often used off-label) — not as a recommendation. Take it only under a qualified clinician's supervision and only as prescribed; do not source it from grey-market vendors, where identity, purity, and dosing are unverified. The evidence below reflects its clinical trials.
What the evidence says
Most Progesterone studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.
Most evidence is from high-quality meta-analyses and randomised trials published 1996–2026 with a typical study size of 266 participants.
Based on 30 studies · 11 meta-analyses · 6 RCTs · 53,320 total participants
Confidence
HighBy outcome
Progesterone has an evidence score of 4.4/10 — moderate evidence based on 30 indexed studies, including 1 meta-analysis. The endogenous steroid hormone, sold as a prescription bioidentical (micronized) drug (Prometrium / Utrogestan). It is the essential ENDOMETRIAL-PROTECTION half of menopausal hormone therapy — it opposes estrogen to prevent endometrial hyperplasia/cancer — and is used for luteal support in IVF and to treat secondary amenorrhea. Oral micronized progesterone is also widely used OFF-LABEL for menopausal SLEEP and hot flashes, because a metabolite (allopregnanolone) is GABA-active and sedating. Randomized trials support these specific indications; in early-pregnancy bleeding (PRISM) benefit was limited to women with prior miscarriages. It is NOT a general healthy-population enhancer, and the breast-cancer signal from older synthetic progestins (WHI) should not be assumed for micronized progesterone, where data suggest it is more breast- and metabolically neutral but longer-term evidence is limited. Prescription-only and NOT a dietary supplement; OTC 'progesterone creams' absorb erratically and are not equivalent. Representative study: PMID 26148507.
Letrozole
Mostly mechanism / observationalA potent non-steroidal aromatase inhibitor (Femara) that blocks estrogen synthesis. Approved for hormone-receptor-positive breast cancer, it is also the evidence-backed first-line drug for ovulation induction in PCOS — where a landmark NEJM RCT showed it BEAT clomiphene on live births. Used off-label in men to raise testosterone and lower estradiol, but that estrogen suppression harms bone and lipids, and in growing boys it carries a vertebral-deformity signal. A prescription drug, not a supplement, and NOT a longevity drug.
Notable regimens that report including Progesterone — documented, not endorsed.
Last reviewed June 2026 · evidence from 30 studies · how we score
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
Progesterone — bioidentical (micronized) progesterone; Prometrium / Utrogestan
The endogenous steroid hormone, sold as a prescription bioidentical (micronized) drug (Prometrium / Utrogestan). It is the essential ENDOMETRIAL-PROTECTION half of menopausal hormone therapy — it opposes estrogen to prevent endometrial hyperplasia/cancer — and is used for luteal support in IVF and to treat secondary amenorrhea. Oral micronized progesterone is also widely used OFF-LABEL for menopausal SLEEP and hot flashes, because a metabolite (allopregnanolone) is GABA-active and sedating. Randomized trials support these specific indications; in early-pregnancy bleeding (PRISM) benefit was limited to women with prior miscarriages. It is NOT a general healthy-population enhancer, and the breast-cancer signal from older synthetic progestins (WHI) should not be assumed for micronized progesterone, where data suggest it is more breast- and metabolically neutral but longer-term evidence is limited. Prescription-only and NOT a dietary supplement; OTC 'progesterone creams' absorb erratically and are not equivalent.
For its specific indications the evidence is real and randomized: the PEPI trial established that adding a progestogen (including micronized progesterone) protects the endometrium from estrogen-driven hyperplasia, a Cochrane review of 94 RCTs supports progesterone for IVF luteal-phase support, and placebo-controlled RCTs show oral micronized progesterone improves menopausal sleep (Caufriez 2011) and reduces vasomotor symptoms (Hitchcock & Prior 2012). In early-pregnancy bleeding (PRISM) benefit was confined to women with prior miscarriages. But these benefits are indication-specific — not a general healthy-population enhancer — it is prescription-only with dose-related sedation, mood and breast-tenderness trade-offs, and long-term breast-outcome data on MICRONIZED (vs synthetic) progesterone remain more limited, keeping the score moderate.
Progesterone is the endogenous steroid hormone (pregn-4-ene-3,20-dione) produced chiefly by the corpus luteum after ovulation and by the placenta in pregnancy.
It prepares and stabilizes the endometrium, supports early pregnancy, and acts in the brain partly through its neurosteroid metabolite allopregnanolone, a positive allosteric modulator of the GABA-A receptor — which is why oral progesterone is sedating.
The pharmaceutical entry here is bioidentical micronized progesterone (brand Prometrium / Utrogestan): the same molecule as the body's own, micronized and oil-suspended to improve absorption, and taken orally (also used vaginally in assisted reproduction). It is a prescription drug, not a dietary supplement.
Its evidence is genuinely strong but indication-bounded.
First and most important, progesterone is the essential endometrial-protection component of menopausal hormone therapy: estrogen given alone to a woman with a uterus drives endometrial hyperplasia and raises endometrial-cancer risk, and adding a progestogen prevents that.
The PEPI trial randomized postmenopausal women to estrogen alone or estrogen plus a progestogen (including micronized progesterone) and showed that the progestogen arms protected the endometrium where unopposed estrogen produced hyperplasia — the foundational reason any woman with a uterus on systemic estrogen also needs progesterone.
Second, progesterone is standard luteal-phase support in IVF/assisted reproduction: a large Cochrane systematic review (van der Linden 2015, 94 RCTs) found luteal-phase support with progesterone improved pregnancy outcomes versus placebo.
Third, oral micronized progesterone is widely used off-label for menopausal sleep and vasomotor symptoms.
A randomized, placebo-controlled crossover study (Caufriez 2011) found progesterone prevented sleep disturbances in postmenopausal women and restored normal sleep architecture, and a placebo-controlled RCT in healthy postmenopausal women (Hitchcock & Prior 2012) found oral micronized progesterone reduced vasomotor symptoms (hot flushes/night sweats) versus placebo.
Fourth, in early-pregnancy bleeding the large PRISM trial (Coomarasamy 2019, NEJM) found vaginal micronized progesterone did NOT significantly improve live births overall, but a prespecified subgroup with one or more previous miscarriages did benefit — an honest, narrow result, not a blanket 'progesterone prevents miscarriage' claim.
Progesterone also treats secondary amenorrhea by inducing a withdrawal bleed. A crucial nuance runs through all of this: micronized (bioidentical) progesterone is not the same as the older synthetic progestins.
The Women's Health Initiative breast-cancer signal came from a combined regimen using a synthetic progestin (medroxyprogesterone acetate, MPA), and observational data (the E3N cohort, Fournier 2008) found that estrogen combined with micronized progesterone was associated with little or no increased breast-cancer risk over several years, in contrast to estrogen plus synthetic progestins — so the WHI signal should be attributed to synthetic progestins, not assumed for micronized progesterone, while acknowledging that long-term randomized breast-outcome data on micronized progesterone are more limited.
The trade-offs are real: oral progesterone commonly causes drowsiness, dizziness, and fatigue (it is taken at bedtime for exactly this reason), and can cause mood changes, bloating, and breast tenderness.
Oral micronized progesterone also has low oral bioavailability because of extensive first-pass hepatic metabolism, which is part of why it is dosed relatively high and at night and why vaginal dosing is preferred for IVF.
Finally, the OTC 'progesterone creams' sold as wellness products absorb erratically and unreliably and are not equivalent to prescription oral micronized progesterone.
The score reflects strong, randomized evidence for its specific indications — endometrial protection, IVF luteal support, sleep, and vasomotor relief — set against the facts that these benefits are indication-specific rather than a general enhancement, that it is prescription-only with sedation/mood trade-offs, and that the long-term breast-safety picture for micronized progesterone, while reassuring relative to synthetic progestins, is not as deeply evidenced.
Progesterone binds the nuclear progesterone receptor and drives secretory transformation of the estrogen-primed endometrium. This opposes estrogen's proliferative drive — the basis for endometrial protection in HRT, luteal support in IVF, and the withdrawal bleed used to treat secondary amenorrhea.
Oral progesterone is metabolized to allopregnanolone, a neurosteroid that positively modulates the GABA-A receptor. This sedating, anxiolytic action explains the improvement in sleep and the drowsiness side effect — and is why oral micronized progesterone is taken at bedtime.
How Progesterone works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
Tap node to isolate • Pinch to zoom • Tap edge for research
Prescription-only and clinician-directed — this is a hormonal prescription drug, not a self-administered supplement, and dosing is indication-specific. For context only: for endometrial protection in menopausal hormone therapy, oral micronized progesterone is commonly ~100 mg daily (continuous-combined) or ~200 mg for ~12 days a month (sequential), taken at bedtime. For IVF luteal support, vaginal progesterone is typically used (e.g. ~90–200 mg twice or three times daily) under a fertility clinic. Doses for sleep/vasomotor use in trials were ~300 mg at bedtime. Oral micronized progesterone is dosed at night because it is sedating and because first-pass metabolism gives it low oral bioavailability.
Take with food
| Form | Type |
|---|---|
| 💊Clinician-prescribed oral micronized progesterone (Prometrium / Utrogestan) at bedtime for HRT endometrial protection and menopausal sleep/vasomotor use — prescription-only | Recommended |
| 🍵Vaginal micronized progesterone (preferred for IVF luteal support; less systemic sedation) | Alternative |
| 💊Synthetic progestins (e.g. medroxyprogesterone acetate, dydrogesterone) — effective for endometrial protection but with a different metabolic/breast profile | Alternative |
| 💊A levonorgestrel intrauterine system for endometrial protection in some HRT regimens | Alternative |
Bioidentical micronized progesterone differs from older synthetic progestins, and OTC 'progesterone creams' are NOT an equivalent substitute. Form and route are a medical decision driven by the indication.
Minimum: 2 weeks
Optimal: 12 weeks
Cycling: Not required
Note: Oral micronized progesterone is taken at bedtime with food because it is sedating and better absorbed that way. For HRT it is taken continuously or sequentially (~12 days/month); for IVF it is given vaginally during the luteal phase. Schedule is clinician-directed and indication-specific, not a fixed supplement routine.
Dose-response data unavailable. The current published research for Progesterone does not provide sufficient dose-specific outcome data to generate reliable dose-response curves.
Refer to the Dosage & Timing section above for recommended dose ranges based on available evidence.
Adding progesterone to estrogen prevents the endometrial hyperplasia and cancer risk that unopposed estrogen causes — the essential reason any woman with a uterus on systemic estrogen also takes a progestogen (PEPI trial).
Progesterone is standard luteal-phase support in assisted reproduction; a Cochrane review of 94 RCTs found it improves pregnancy outcomes versus placebo. Vaginal dosing is commonly used for this indication.
Via its GABA-active metabolite allopregnanolone, oral micronized progesterone prevented sleep disturbances and restored normal sleep architecture in postmenopausal women in a placebo-controlled crossover study (Caufriez 2011).
A placebo-controlled RCT in healthy postmenopausal women found oral micronized progesterone reduced hot flushes and night sweats versus placebo (Hitchcock & Prior 2012).
The same allopregnanolone-GABA action that aids sleep commonly causes daytime drowsiness, dizziness, and fatigue — which is why oral micronized progesterone is taken at bedtime.
Progesterone can cause mood changes (some women feel low or irritable), bloating, and breast tenderness. These are dose-related and a common reason for switching dose, route, or regimen.
Progesterone's benefits are tied to specific indications (endometrial protection, IVF luteal support, menopausal sleep/vasomotor symptoms). In early-pregnancy bleeding the PRISM trial found benefit only in women with prior miscarriages, and there is no evidence it enhances health in people without an indication.
This is the core indication — a progestogen (micronized progesterone or an alternative) is REQUIRED to protect the endometrium. Do not take systemic estrogen alone if you have a uterus.
Progesterone luteal support is standard; vaginal dosing is commonly used. Follow the fertility clinic's protocol.
PRISM found benefit only in those with one or more previous miscarriages — not a blanket treatment. Use only on obstetric advice.
Caution or avoid — discuss individualized risk. The WHI breast-cancer signal came from a SYNTHETIC progestin (MPA); micronized progesterone appears more breast-neutral observationally, but long-term randomized data are limited.
Not supported — benefits are indication-specific, not a general enhancer, and OTC progesterone creams are not equivalent to prescription micronized progesterone.
Oral progesterone is sedating via its allopregnanolone metabolite; combining it with alcohol or other CNS depressants can add to drowsiness and impairment.
Strong enzyme inducers can accelerate progesterone metabolism and lower its levels, potentially reducing endometrial protection in HRT.
Tip: Driven by the sedating allopregnanolone metabolite of oral progesterone. Take at bedtime; avoid driving soon after dosing and avoid combining with alcohol.
Tip: Common and usually dose-related; often settles with time or a dose/regimen adjustment by the clinician.
Tip: Some women feel low or irritable on progesterone (especially sequentially). Discuss dose, route (vaginal vs oral), or progestogen choice with the prescriber.
Tip: Generally mild; report persistent or severe headache, which can warrant review.
The commonly studied dose of Progesterone is Prescription-only and clinician-directed — this is a hormonal prescription drug, not a self-administered supplement, and dosing is indication-specific. For context only: for endometrial protection in menopausal hormone therapy, oral micronized progesterone is commonly ~100 mg daily (continuous-combined) or ~200 mg for ~12 days a month (sequential), taken at bedtime. For IVF luteal support, vaginal progesterone is typically used (e.g. ~90–200 mg twice or three times daily) under a fertility clinic. Doses for sleep/vasomotor use in trials were ~300 mg at bedtime. Oral micronized progesterone is dosed at night because it is sedating and because first-pass metabolism gives it low oral bioavailability.. Individual needs vary — start at the lower end of the range and adjust based on how you respond.
The best time to take Progesterone is before bed. Take it with food. Oral micronized progesterone is taken at BEDTIME because its GABA-active metabolite allopregnanolone is sedating — taking it earlier causes daytime drowsiness/dizziness.
Progesterone is generally safe at recommended doses, with a few precautions worth noting. The most commonly reported side effects are drowsiness / dizziness / fatigue, breast tenderness, mood changes / low mood / irritability. Use caution if any of these apply to you: Use without a prescription / without medical supervision — progesterone is a prescription hormonal drug, not a dietary supplement; Known or suspected breast cancer or other progesterone-sensitive cancer (per product labeling); Active or history of venous thromboembolism, arterial thromboembolic disease, or known thrombophilia (combined HRT context).
Lactoferrin
Mostly mechanism / observationalA multifunctional iron-binding glycoprotein from milk with broad antimicrobial, anti-inflammatory, and immune-modulating properties.
Not an adverse interaction but the intended pairing — in women with a uterus, progesterone is added specifically to oppose estrogen and protect the endometrium. Estrogen should not be taken alone in such women.
Tip: Common when starting HRT; persistent or heavy/unexpected bleeding should be evaluated to rule out other causes.
Tip: Thrombosis risk in HRT is driven mainly by the estrogen and route; seek urgent care for leg swelling/pain, chest pain, or breathlessness. Assess personal/family clot risk before starting.