Myo/D-chiro inositol 40:1: Cochrane meta-analysis of 22 RCTs confirms ovulation benefit
Source: Cochrane Database of Systematic Reviews, April 18, 2026
Summary
A Cochrane systematic review published April 2026 analyzes 22 randomized controlled trials (1,847 women with Rotterdam-criteria PCOS) on the efficacy of myo-inositol/D-chiro-inositol at the 40:1 ratio. Primary results: ovulation rate at 3 months +32% vs placebo (OR 2.41, 95%CI 1.87-3.11, I2=42%). Cycle regularity at 6 months: +28% vs placebo. LH reduction: -22% (low certainty). Free testosterone reduction: -15% (moderate certainty). HOMA-IR improvement: -18% vs placebo. Comparison with metformin: comparable effects on cycle regularity; metformin superior for insulin resistance (small difference). Validated dose: 2000mg myo-inositol + 50mg D-chiro-inositol (40:1 ratio), twice daily for 3 months or more. Side effects: excellent profile, equivalent to placebo. Limitations: heterogeneity in diagnostic criteria, maximum follow-up 6 months in most studies. Cochrane conclusion: inositol at 40:1 ratio is a safe intervention with moderate-quality evidence for improving ovulation in PCOS.
Why it matters for you
This is one of the strongest pieces of evidence available for any supplement in PCOS. If you're looking to improve cycle regularity or natural fertility, inositol 40:1 is worth discussing with your doctor or gynecologist — the validated dose (4000mg total/day) is widely available in pharmacies.