Inositol is a six-carbon ring compound (a cyclitol); myo-inositol is the form most used and studied. As a supplement it is used mostly by women with polycystic ovary syndrome (PCOS), where it has been studied for insulin resistance and hormone levels, often alone or with D-chiro-inositol.
Also known as: myo-inositol, D-chiro-inositol.
Inositol has no intake value or upper limit, and there is no NIH fact sheet for it. A 2011 safety review (Carlomagno and Unfer) found that only the highest amount studied, 12 g a day, caused mild stomach side effects. These are study protocols, not a recommendation.
It is sold in the US as a dietary supplement. Under the 1994 dietary supplement law (DSHEA), FDA does not approve dietary supplements before they are marketed, and the maker, not FDA, is responsible for safety and labeling. There is no FDA-approved inositol drug.
A 2017 meta-analysis (Unfer) of 9 randomized trials in women with PCOS (247 treated, 249 controls) found lower fasting insulin and HOMA insulin-resistance scores with myo-inositol, alone or with D-chiro-inositol. Testosterone showed only a trend toward lower levels, androstenedione did not change, and SHBG rose only in studies lasting at least 24 weeks.
A 2011 safety review (Carlomagno and Unfer) found little published information on side effects; only 12 g a day caused mild nausea, gas and diarrhea, and the side effects did not get worse as the dose rose. If you take metformin or another diabetes medicine, tell your prescriber you take inositol.
We could not find a single published half-life or time to peak for myo-inositol that applies to a supplement dose, so we do not list one.
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