Supplement
Inositol (Myo-Inositol)
One of the best-evidenced supplements in women's metabolic health.
Myo-inositol is a sugar alcohol that acts as a second messenger in insulin and FSH signaling. We grade Inositol (Myo-Inositol) B on evidence and B- for worth-it at about $15-30 per month.
Evidence
Worth it
Typical cost: $15-30/month
What it does
Myo-inositol is a sugar alcohol that acts as a second messenger in insulin and FSH signaling. In PCOS, inositol metabolism is disrupted, which is why supplementation at the physiological 40:1 myo-to-D-chiro ratio restores both metabolic and reproductive signaling.
What the research says
Improves insulin sensitivity and lowers fasting insulin in PCOS
Evidence: strong. Multiple meta-analyses of RCTs show myo-inositol significantly reduces fasting insulin and HOMA-IR; a 2026 umbrella review of 13 meta-analyses confirmed the HOMA-IR effect (MD -1.14) with consistent direction across trials.
Restores ovulation and menstrual regularity in PCOS
Evidence: strong. A BJOG meta-analysis of 13 RCTs (1,473 women) found inositol improved ovulation rates (OR 6.93) and menstrual frequency; the umbrella review confirmed higher ovulation rates (RR 2.75) and live births (RR 2.29).
Lowers androgens and improves lipid markers in PCOS
Evidence: moderate. Meta-analyses show reduced total and free testosterone, higher SHBG, lower LH, and triglyceride reductions around 30 mg/dL; effects versus metformin are mostly non-significant except for triglycerides and pregnancy rates.
This is the strongest evidence base in this batch: replicated RCT meta-analyses across metabolic, hormonal, and reproductive outcomes, with a clean safety profile. It stays at B rather than higher because most data are PCOS-specific and GRADE certainty is largely low to moderate, with effects outside PCOS less studied.
What the experts say
Every position links to its source. We include skeptics alongside supporters.
International Society of Gynecological Endocrinology
Consensus statement recommends the 40:1 myo-to-D-chiro inositol ratio as the reference formulation for PCOS.
Is it worth it?
Derived from the October 2026 worth-it model: B evidence at about $22.5 a month, targeted applicability, scored as evidence squared over the square root of cost.
Typical cost
$15-30/month
Common form, not a brand recommendation
Dosage contextestablished
Clinical standard is 2 g myo-inositol twice daily (4 g total), or 4 g once daily, typically in the 40:1 myo-to-D-chiro ratio. Effects build over 12+ weeks.
Safety notes
Excellent safety profile across trials, comparable to placebo with no severe adverse events reported. Mild GI upset is occasionally reported at higher doses. Standard cautions apply in pregnancy; discuss with a clinician.
Longevity Lab Report
Inositol (Myo-Inositol) news, graded when it happens.
The grade on this page stays free. The reporting goes further in the email: new studies, dose debates, and expert shifts on inositol (myo-inositol), including stories that never get posted here.
Frequently asked questions
Is Inositol (Myo-Inositol) safe?
Excellent safety profile across trials, comparable to placebo with no severe adverse events reported. Mild GI upset is occasionally reported at higher doses. Standard cautions apply in pregnancy; discuss with a clinician.
What is the right dose of Inositol (Myo-Inositol)?
Clinical standard is 2 g myo-inositol twice daily (4 g total), or 4 g once daily, typically in the 40:1 myo-to-D-chiro ratio. Effects build over 12+ weeks.
Is Inositol (Myo-Inositol) worth taking?
We grade Inositol (Myo-Inositol) B- for worth-it at a typical cost of $15-30 per month. Derived from the October 2026 worth-it model: B evidence at about $22.5 a month, targeted applicability, scored as evidence squared over the square root of cost.
Changelog
Last updated 2026-10-17
- 2026-10-16|New DRAFT entry, batch 3.
- 2026-10-17|Applicability assigned (targeted) for the worth-it leaderboard methodology update of 2026-10-17.
- 2026-10-17|Worth-it grade derived from the October 2026 worth-it model (same gated model as the leaderboard); applicability recorded for all records.