Fertility · PCOS
Myo-Inositol for PCOS and Fertility: Dose, Ratio, and Evidence
Myo-inositol is a B-vitamin-like sugar alcohol that acts as a second messenger for insulin and FSH signaling in the ovary. In women with PCOS — and in many TTC patients without a formal diagnosis — supplementing myo-inositol improves ovulatory cycles, egg quality, and insulin sensitivity. Here's the evidence and the dose that matters.
What myo-inositol actually does
Myo-inositol participates in two ovarian pathways: FSH signaling (egg maturation) and insulin signaling (glucose handling). In PCOS, where insulin resistance disrupts both, supplementation restores cycle regularity in roughly 60–70% of women within 3–6 months.
The 40:1 ratio
Your body uses two inositol isomers — myo and d-chiro — at a roughly 40:1 ratio in plasma. Products that load too much d-chiro (the cheaper isomer) actually worsen oocyte quality in normal-weight PCOS. The 40:1 ratio is the supported formulation.
Evidence summary
Meta-analyses (Pundir 2018, Greff 2023) consistently show improvements in ovulation rate, clinical pregnancy rate, and metabolic markers (HOMA-IR, fasting insulin) compared to placebo, with effect sizes comparable to metformin and a far better tolerability profile.
Where it fits
Inositol is foundational for any TTC plan with PCOS, irregular cycles, or known insulin resistance. Pair with CoQ10 for egg quality and a quality prenatal. If cycles remain irregular after 3 months, request a fertility consult.
Related
Frequently asked questions
What ratio of myo to d-chiro inositol works?
The 40:1 myo-to-d-chiro ratio matches physiological plasma levels and is the ratio with the strongest PCOS evidence (Nordio 2019, Unfer 2017). kindr Egg Quality uses this ratio.
How much should I take?
Standard dosing is 2 g twice daily (4 g total) for at least 90 days before conception attempts or before an IVF cycle.
Does inositol work if I do not have PCOS?
Yes — benefits on oocyte quality and insulin sensitivity have been documented in non-PCOS IVF patients as well, though effects are largest in insulin-resistant phenotypes.
Can I take it with metformin?
They can be used together, but coordinate with your clinician — combining may amplify GI side effects.
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Medically reviewed by Dr. Ana Lisa Carr, MD, MBA · Last reviewed 2026-06-23. Compounded medications are prepared by FDA-registered 503A pharmacies and are not FDA-approved drug products.