Myo-inositol
Content by: OpenSupplement Editorial Team | Medical review: pending | Last updated: April 13, 2026
TL;DR
Pseudo-vitamin involved in cellular signaling and insulin sensitivity
High evidence for metabolic syndrome and PCOS support
Low evidence for sleep, though it may improve architecture via serotonin signaling
Excellent safety profile; naturally found in the brain
Cost: ~$10-20/month
Best for: Insulin resistance, PCOS, anxiety-driven sleep issues
What it is
Myo-inositol was once classified as Vitamin B8, though it's actually a sugar alcohol that the body can produce itself. It is a major component of cell membranes and acts as a 'secondary messenger,' helping hormones like insulin and neurotransmitters like serotonin communicate with cells.
In the brain, inositol is highly concentrated and helps regulate the 'sensitivity' of various receptors. This makes it a popular choice for both metabolic health (insulin sensitivity) and mental health (anxiety and OCD).
What the research says
This is where inositol is most proven. Insulin Sensitivity. A meta-analysis published in Endocrine Connections showed that myo-inositol significantly reduces fasting insulin and HOMA-IR (a measure of insulin resistance). PCOS. It is a first-line natural treatment for Polycystic Ovary Syndrome, with multiple studies showing it can restore ovulation and improve metabolic markers as effectively as Metformin but with fewer side effects. Lipids. It also shows modest benefit in lowering LDL cholesterol and triglycerides. [1][2]
The data for sleep is mostly theoretical and anecdotal. The Serotonin Link. Because inositol is involved in serotonin signaling, it may help 'stabilize' the brain's nighttime activity. The Evidence. There are very few RCTs specifically for sleep; one study in pregnant women showed improved sleep quality, but broad population data is lacking. Verdict. If you are already taking it for metabolic health or anxiety, you may notice a sleep 'side effect' benefit, but it's not a primary sleep inducer. [3]
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Myo-inositol on Amazon
Safety
Extremely safe even at high doses (up to 18 grams). The only common side effect is mild diarrhea or GI upset at very high dosages.
Interactions
None significant. It has a very clean safety profile and does not typically interact with common medications.
Dosing
For Metabolic Support/PCOS: 2,000-4,000 mg daily. For Anxiety/Sleep: 2,000-12,000 mg (higher doses are often used for psychological support). Form: Powder is easiest for high-dose use.
Cost
Affordable. Monthly cost for metabolic doses is $10-20.
The bottom line
Myo-inositol is a metabolic powerhouse with bonus 'calming' benefits. If you have insulin resistance and poor sleep, it's a very logical addition to your stack.
References
- Croze ML, Soulage CO. Potential role and therapeutic interests of myo-inositol in metabolic diseases. Biochimie. 2013;95(10):1811-27.
- Unfer V, Nestler JE, Kamenov ZA, et al. Effects of inositol(s) in women with PCOS: a systematic review of randomized controlled trials. Int J Endocrinol. 2016;2016:1849162.
- Garzon S, Laganà AS, Monastra G, et al. Association between inositol supplementation and sleep quality: a systematic review. Eur Rev Med Pharmacol Sci. 2019;23(3):1019-1029.
Sources for this page include published meta-analyses, systematic reviews, and NIH dietary supplement fact sheets. All claims reflect the evidence as of early 2026.
This is not medical advice. Consult your healthcare provider before starting any supplement, especially if you take medications.