Comparison guide
Which inositol should you take?
Myo-inositol is the form behind most of the PCOS evidence; D-chiro-inositol is a related isomer usually added in small amounts, and D-pinitol is a methylated inositol from carob and soy. What matters is which form has actually been tested for your goal, and whether more of a minor isomer could backfire.
The options, compared
| Option | Evidence | Best for | The honest note | |
|---|---|---|---|---|
| Inositol (Myo-Inositol) | Moderate evidence | PCOS and insulin resistance | Moderate evidence for better insulin markers, cycle regularity and ovulation in PCOS, usually at 2 g twice daily for 12–24 weeks. Evidence for preventing gestational diabetes and for anxiety is limited. | View |
| D-Chiro-Inositol | Limited evidence | Small add-on in 40:1 blends | The original 1999 trial was not reproduced by other groups, and doses of 600 mg/day and above may worsen oocyte quality. The 40:1 myo-to-D-chiro ratio is plausible but not shown to beat myo alone. | View |
| D-Pinitol | Limited evidence | Evidence too thin to bother | Small trials on glucose response are mixed, and one in older adults found no improvement in glucose tolerance. Long-term safety is unstudied. | View |
Our verdict
Myo-inositol at 2 g twice daily is the default and the form to choose if you take only one. D-chiro-inositol belongs in a small 40:1 ratio alongside myo rather than on its own, and D-pinitol has too little evidence to be worth buying. If you take metformin, insulin or sulfonylureas, monitor your glucose.