Supplement analysis backed by scientific evidence · PT

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Moderate evidenceWomen's health

Inositol (Myo-Inositol)

Myo-inositol improves insulin resistance and ovulation in PCOS with a benign side effect profile, making it one of the more defensible supplements in women's health. Its use for preventing gestational diabetes and for anxiety is much weaker than the marketing suggests.

What the science says

  • Improves metabolic and hormonal parameters in PCOS Moderate evidence

    A meta-analysis of 26 randomised trials in PCOS found inositol significantly reduced fasting insulin and HOMA-IR and improved testosterone and menstrual regularity versus placebo, with effects broadly comparable to metformin but far better tolerated. Trials were generally small and short (8-24 weeks) and outcome definitions varied, which keeps this at moderate rather than strong.

  • Increases ovulation and clinical pregnancy rates in PCOS Moderate evidence

    Pooled trial data show higher ovulation and clinical pregnancy rates with myo-inositol versus placebo in women with PCOS, though live birth data — the outcome that actually matters — are sparse and imprecise. Head-to-head comparisons with metformin show similar ovulation rates with fewer gastrointestinal side effects.

  • Prevents gestational diabetes Limited evidence

    A 2023 Cochrane review of seven trials (1,319 women) rated the evidence for myo-inositol reducing gestational diabetes as low-certainty, with wide confidence intervals and trials concentrated in a small number of Italian centres. Promising but not yet dependable — the review explicitly called for larger trials before routine use.

  • Reduces anxiety, panic attacks, or OCD symptoms Limited evidence

    Small crossover trials from the 1990s using 12-18 g/day reported reductions in panic attack frequency and depressive symptoms, but sample sizes were in the tens and replication has been minimal. The doses required are large and unpleasant to take, and modern controlled evidence is essentially absent.

Dosage & safety

Studied dosePCOS trials most often used 2 g myo-inositol twice daily (4 g/day), frequently combined with 400 mcg folic acid, for 12-24 weeks. Many products use a 40:1 myo-inositol to D-chiro-inositol ratio, mirroring physiological plasma ratios, though the superiority of that specific ratio is not firmly established. Gestational diabetes prevention trials used 2-4 g/day from the first or second trimester. Psychiatric trials used 12-18 g/day. Effects on insulin sensitivity typically take 8-12 weeks to appear.
SafetyVery well tolerated; the main side effects are nausea, flatulence and loose stools, mostly at doses above 12 g/day. No serious adverse events have been reported in PCOS or pregnancy trials, and 2-4 g/day is considered safe in pregnancy, though this rests on modest trial numbers. Theoretical additive hypoglycaemia with metformin, sulfonylureas or insulin — monitor if combining. High-dose D-chiro-inositol alone has been reported to worsen oocyte quality in some work, which is the rationale for myo-inositol-dominant ratios. Isolated reports of hypomania at psychiatric doses in bipolar disorder. Not banned in sport and no prescription restrictions in most countries.

Scientific references

Where to buy

Protocol for Life Balance, Myo-Inositol Powder, 1 lb (454 g)

View on iHerb

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