This systematic review of 10 sources, including one meta-analysis and multiple randomized controlled trials, examined the timeline for inositol’s effects on PCOS symptoms. The evidence indicates that improvements occur along a predictable timeline that varies by outcome type. The earliest benefits appear within 6-8 weeks, including significant improvements in insulin sensitivity, ovulation rates (86% vs 27% placebo), serum testosterone, blood pressure, and triglycerides. By 12 weeks, myo-inositol supplementation consistently demonstrates significant reductions in LH, insulin levels, HOMA-IR, and restoration of menstrual cyclicity. Menstrual regularity was restored in 68-100% of patients by 6 months.

Certain outcomes require longer treatment duration. A meta-analysis found that SHBG levels significantly increased only when myo-inositol was administered for at least 24 weeks, with shorter durations showing no significant effect on this parameter. Similarly, improvements in acne required at least 6 months of supplementation. These findings suggest a hierarchical response pattern: insulin sensitization occurs first (6-8 weeks), followed by hormonal normalization (12 weeks), and finally improvements in androgenic clinical features (≥24 weeks). The type of inositol may influence response timing, with D-chiro-inositol showing rapid ovulatory effects and myo-inositol demonstrating broader metabolic benefits over longer periods. Continuous administration appears necessary to maintain benefits.