Verified Supplement Data Primary-sourced

Myo-Inositol Guide (2026): PCOS Evidence, the 40:1 Ratio & Dose

By Erin Rose · Updated · Methodology · About Us

Myo-inositol is the best-evidenced supplement for PCOS. Randomized trials show it improves insulin sensitivity, restores ovulation, and lowers androgens in many women — often compared to metformin but far better tolerated. The dose that was actually studied is 2 g twice daily (4 g total), and the trials that combined it with D-chiro-inositol used the physiological 40:1 myo-to-D-chiro ratio — a detail most bottles get wrong. Below: the evidence, the ratio, and dosing.

Verified picks (40:1 ratio, at the 4 g/day trial dose)

Certified pick
Ovasitol by Theralogix 90-day supply

NSF Certified, pre-measured packets, 90 daily doses per box — the only third-party-certified option we track.

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Budget pick
Micro Ingredients Myo & D-Chiro Inositol Powder 40:1

Same 2,000/50 mg 40:1 blend as loose powder — about a third of Ovasitol's daily cost.

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About our data

Every comparison uses clinical evidence from PubMed systematic reviews, product label data from the NIH Dietary Supplement Label Database, and third-party certifications (USP, NSF). Products are ranked by cost per clinically-effective dose. See our methodology and editorial standards.