Inositol
Sometimes called vitamin B8. Isn't one, but does a job or two of one.
Inositol is a sugar-alcohol the body synthesises itself, which is why it lost its "vitamin B8" designation once true dietary shortfall was shown to be essentially impossible. The most-studied form, myo-inositol, has meaningful evidence for insulin sensitivity, particularly in women with polycystic ovary syndrome (PCOS), where the standard dose is 2g twice a day. D-chiro-inositol has a smaller research base of its own, and the 40:1 myo-to-D-chiro ratio is a specific combination that mirrors the ratio found naturally in plasma. IP6 (inositol hexaphosphate) is a distinct compound studied more for antioxidant effects than for the metabolic uses of myo-inositol.
Forms and bioavailability
Not all forms are absorbed equally. The form on your supplement label affects how much your body can actually use.
| Form | Absorption | With food | Timing | Evidence |
|---|---|---|---|---|
| inositol hexaphosphate (IP6) | Lower | Either | Either | Possible |
| D-chiro-inositol | Typical | Either | Either | Likely |
| myo + D-chiro (40:1) | Typical | Either | Either | Likely |
| myo-inositol | Typical | Either | Either | Strong |
How it pairs with other supplements
Works well with
Both are phospholipid precursors; often combined in lipotropic formulations for cell membrane support.
Stack Almanac tracks which inositol form you're taking, since myo-inositol and D-chiro-inositol are studied for different reasons at very different doses despite sharing the same headline name.
Track your Inositol in Stack Almanac
Last reviewed: 2026-07-22. Reference values are adult-general RDAs. Individual needs may vary. This page is for informational purposes only and is not a substitute for professional medical advice.