Myo-inositol

Also known as inositol, myoinositol, vitamin b8.

Last reviewed October 9, 2026 · Jump to references

What is Myo-inositol?

In plain words

Myo-inositol is a sugar-like substance found in foods and made by the body. The body uses it to build cell membranes and carry signals inside cells, including signals related to insulin. Researchers study it for blood sugar control and polycystic ovary syndrome (PCOS), a condition that affects hormone balance and menstrual cycles. Evidence for clinical benefits remains limited, and supplements can cause stomach upset or diarrhea.

Technical definition

Myo-inositol is a naturally occurring six-carbon cyclic polyol and the predominant inositol stereoisomer in humans; despite the nickname “vitamin B8,” it is not an essential vitamin because the body can synthesize it. It serves as a precursor to membrane phosphoinositides and inositol phosphate second messengers, supporting intracellular signaling downstream of receptors, including pathways involved in insulin action and calcium regulation. In the United States, it is marketed as a dietary supplement, not an FDA-approved treatment for polycystic ovary syndrome (PCOS) or diabetes.

Educational information only. This page does not provide medical advice or determine whether a supplement is appropriate for you. Review supplements with a qualified healthcare professional, especially if you take medication, are pregnant, have surgery scheduled, or have a chronic medical condition.

Evidence by use

Each use is rated on its own. There is no single overall effectiveness score.