Myo-Inositol (Inositol · PCOS & Insulin Sensitivity Support)
| CAS No. | 87-89-8 |
| Class | Carbohydrate · Sugar alcohol · Cyclitol |
| Source | All plants — ubiquitous in cell membranes; commercial production via phytic acid hydrolysis from rice bran or corn |
| Claim strength | High |
| Availability | Coming soon — Request pricing and availability → |
Myo-inositol is a naturally occurring polyol that serves as a structural component of phospholipid cell membranes and as a second messenger in intracellular insulin signalling cascades. It is present in all plant and animal cells and found in the human diet in fruits, beans, grains, and nuts. Although sometimes called "Vitamin B8," myo-inositol is not a true vitamin — it can be synthesised by the body from glucose-6-phosphate. It is the most clinically studied inositol stereoisomer and the primary active in evidence-based PCOS and insulin sensitivity supplement formulations.
Myo-Inositol for PCOS, Insulin Sensitivity & Hormonal Balance — Clinical Evidence
PCOS — the primary clinical application: Women with polycystic ovary syndrome have documented deficiencies in inositol phosphoglycans, impairing insulin signal transduction in ovarian tissue. Multiple RCTs in PCOS patients demonstrate that myo-inositol supplementation at 2–4g per day significantly reduces fasting insulin, improves menstrual cycle regularity, reduces testosterone levels, and improves ovulation rates. Several comparative trials show effects comparable to metformin — with a substantially better tolerability profile.
Insulin sensitivity: Myo-inositol acts as a secondary messenger in the insulin signalling pathway — it is required for proper intracellular insulin signal transduction. Supplementation improves peripheral insulin sensitivity in populations with insulin resistance, including PCOS patients and women with gestational diabetes. This is one of the more mechanistically well-understood insulin sensitisation pathways available for supplement formulation.
Mood and anxiety support: RCTs have examined myo-inositol for panic disorder and OCD — two conditions linked to altered phosphoinositide second messenger signalling. Effects documented in small but well-designed trials. Mood support is a secondary positioning angle with genuine mechanistic rationale but thinner evidence than the PCOS application.
40:1 myo-inositol to D-chiro-inositol combination: The combination of myo-inositol and D-chiro-inositol at a 40:1 ratio mirrors the physiological plasma ratio and is the most studied combination format specifically for PCOS. Multiple RCTs confirm superior outcomes for this combination versus myo-inositol alone for ovulation and hormonal parameters.
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Myo-Inositol Dosage, Format & Formulator Specification
Standard dose: 2–4g per day. The PCOS clinical evidence base predominantly uses 4g per day. Powder sachet dissolved in water is the dominant commercial format — myo-inositol is sweet, water-soluble, and palatable without flavour masking, making it one of the rare supplement actives naturally suited to a powder drink format.
40:1 combination formulations: For PCOS-specific products, combine myo-inositol with D-chiro-inositol at a 40:1 ratio — e.g. 1,800mg myo-inositol with 200mg D-chiro-inositol as a starting point. This mirrors physiological plasma ratios and has the strongest RCT evidence base for PCOS hormonal outcomes.
Stability: Myo-inositol is highly stable — 24+ month shelf life under ambient storage. Compatible with standard sachet, capsule, and tablet manufacturing. No special handling required.
Pairs with: D-chiro-inositol (40:1 PCOS formulation), folate (fertility support stacks), N-acetylcysteine (PCOS antioxidant combination), alpha-lipoic acid (insulin sensitivity stacks).
Frequently Asked Questions — Myo-Inositol
What is myo-inositol and how does it differ from other inositol forms?
Myo-inositol is one of nine possible stereoisomers of inositol — it is by far the most abundant in nature and the most clinically studied. D-chiro-inositol is the second most studied, with specific roles in hepatic and ovarian insulin signalling. The 40:1 myo-inositol to D-chiro-inositol combination has the strongest evidence for PCOS. Other stereoisomers (scyllo, muco, neo, etc.) have minimal supplement relevance.
Is myo-inositol effective for PCOS?
Yes — multiple RCTs document significant improvements in fasting insulin, menstrual regularity, testosterone levels, and ovulation rates at 2–4g per day. Comparative trials versus metformin show comparable efficacy for hormonal outcomes with better tolerability. The evidence base is now sufficient to consider myo-inositol a first-line nutritional intervention for PCOS in several clinical guidelines.
What is the clinical dose for myo-inositol?
The majority of PCOS RCTs use 4g per day in two divided doses of 2g. The 2g dose has also shown effects in some trials. For mood support applications, doses of 12–18g per day have been used in psychiatric research but are impractical for standard supplement formats — the PCOS dose range is the commercially relevant specification.
Can myo-inositol be combined with metformin?
The combination has been studied — some trials suggest additive benefit on insulin sensitivity and ovarian function in PCOS patients already on metformin. However, this is a medication co-administration context that requires medical supervision. For supplement labels, do not make claims about interactions with prescription medications — direct users to consult a healthcare professional.