Myo-inositol
Sugar alcohol with RCT signal for PCOS, comparable to metformin for ovulation restoration and metabolic markers.
Why
Myo-inositol is a sugar alcohol that functions as a second messenger in insulin and FSH signalling. Multiple RCTs in polycystic ovary syndrome (PCOS) report improvements in menstrual regularity, ovulation rate, hyperandrogenism markers, and insulin resistance, effects comparable to metformin in head-to-head trials. The 40:1 myo-inositol to D-chiro-inositol ratio (physiological ratio) is the most-studied formulation.
How it works
Component of inositol phosphoglycan second messengers that mediate insulin action at the post-receptor level. In ovarian theca cells, supports FSH signalling and oestrogen synthesis. In skeletal muscle, supports GLUT4 translocation. Restores the disrupted myo:D-chiro inositol balance documented in PCOS.
Expected onset · Cycle regularity changes over 3–6 months; metabolic markers over 8–12 weeks
How to take
Dosage
PCOS: 2 g twice daily (4 g/day total), often in a 40:1 myo:D-chiro-inositol ratio. Trials run 3–6 months.
Timing
Twice daily with food
On the label
'Myo-inositol' with stated milligrams, or '40:1 myo-inositol : D-chiro-inositol' for the physiological-ratio formulation. Avoid pure D-chiro-inositol products (different effect, not equivalent).
Ideal for
Women with PCOS, menstrual irregularity, hirsutism, fertility complaints; women undergoing IVF with PCOS phenotype.
Safety
Evidence
Unfer 2017 Endocr Connect meta-analysis (9 RCTs): myo-inositol improved insulin sensitivity, ovulation rate and total testosterone in PCOS vs placebo, with effects comparable to metformin in head-to-head trials. Costantino 2009 RCT: 4 g/day improved menstrual regularity and insulin sensitivity over 12 weeks. Strong direction of effect with very favourable tolerability profile.
- Costantino et al., Eur Rev Med Pharmacol Sci 2009, myo-inositol vs placebo in PCOS (RCT)
- Unfer et al., Endocr Connect 2017, myo-inositol for treatment of PCOS: systematic review and meta-analysis
- Raffone et al., Gynecol Endocrinol 2010, insulin sensitiser agents alone and in co-treatment with rFSH for ovulation in PCOS (RCT, myo-inositol vs metformin)
Where to get it
Shop Myo-inositol on AmazonSponsored · As an Amazon Associate, Healicus earns from qualifying purchases.