Other ·Moderate evidence ·Reviewed May 2026
Myo-inositol and D-chiro-inositol are inositol stereoisomers used most often in a 40:1 ratio for polycystic ovary syndrome support. Evidence suggests possible improvements in ovulation, menstrual regularity, insulin resistance, and some androgen markers, but guideline reviews rate certainty as limited and outcomes vary. It should be used as an adjunct to evidence-based PCOS care, not as a replacement for evaluation of infertility, diabetes risk, or abnormal bleeding.
The bottom line
Evidence rating moderate. Most-documented uses: may support ovulation in pcos, may improve menstrual regularity, may improve insulin resistance markers. 3 sources indexed (2015–2024), with 3 interaction records on file.
Core mechanism
Inositol phosphoglycans act as second messengers in insulin and follicle-stimulating hormone signaling. Myo-inositol is important in ovarian follicle signaling and oocyte environment, while D-chiro-inositol is more closely linked to insulin-mediated glycogen and androgen pathways. A 40:1 myo-inositol to D-chiro-inositol ratio is intended to approximate physiologic plasma balance and avoid excessive D-chiro-inositol exposure that may be unfavorable for ovarian function.3,1
Can be taken with or without food. Splitting twice daily may improve GI tolerance and steady exposure.
Ranked by evidence and value.
Real-world pricing across three quality tiers. Assumes 40:1 inositol powder.
Powders are usually cheaper per gram than capsules at clinically used doses. Updated 2026-06-04.
Dose: 2,000 mg myo-inositol plus 50 mg D-chiro-inositol twice daily2,1
Timing: Morning and evening
Assess cycles over 3-6 months.
Dose: 4,000 mg/100 mg daily in 40:1 ratio3
Timing: Divided twice daily
Pair with nutrition, exercise, sleep, and metabolic screening.
Dose: 2-4 g/day myo-inositol with or without DCI
Timing: Daily
Abnormal bleeding, severe pain, or prolonged amenorrhea needs evaluation.
What to test, the optimal window inside the conventional range, and how long a response takes.
May decrease fasting insulin or HOMA-IR in insulin-resistant PCOS.3
Interpret with fasting glucose, A1c, and clinical context.
May reduce androgen excess markers in some PCOS users.
Use high-quality assays and interpret with SHBG and free testosterone when possible.
Where this appears in the symptom-to-supplement map, ranked by relevance.
Improved insulin and ovarian signaling may support ovulatory cycles in PCOS.3
Amenorrhea or abnormal bleeding needs evaluation.
Inositol second messengers support insulin signaling.3,1
Use with lifestyle and metabolic screening.
May lower insulin-driven ovarian androgen signaling in some PCOS users.3,1
Dermatologic and endocrine treatments may be needed.
Evidence-based stacks that include it, with the exact dose and timing each one uses.
Inositols act as insulin second messengers and are the most studied PCOS supplement, improving insulin sensitivity, lowering androgens, and restoring ovulation; the physiological 40:1 myo to D-chiro ratio mirrors plasma levels and is the best-supported form.3
Both may improve insulin resistance and can increase the chance of low-glucose symptoms when combined with diabetes medications or low calorie intake.
Recommendation: Monitor glucose symptoms and avoid adding both at full dose simultaneously when using glucose-lowering medication.
Both are used for insulin sensitivity and may have additive glucose-lowering effects.
Recommendation: Start one product at a time and monitor dizziness, sweating, shakiness, or glucose readings when relevant.
Folate is often paired with inositol in reproductive-age PCOS users, especially when pregnancy is possible.
Recommendation: Ensure prenatal folate needs are met, but coordinate fertility and pregnancy use with a clinician.
Search all 3 interaction records for Myo-Inositol & D-Chiro-Inositol →
Numbered references. Citations throughout the page link here.
Inositol may improve some metabolic and reproductive PCOS outcomes, but evidence certainty was limited for several endpoints.
The 40:1 ratio was associated with better ovulation restoration than several other tested ratios.
Consensus review described biologic rationale and clinical use patterns for MI and DCI in PCOS.
This page is educational. Do not start, stop, or change a supplement or medication based on it without checking with a qualified healthcare professional.
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