Inositol: Myo-Inositol, D-Chiro-Inositol and What Research Shows

Inositol is a sugar-like compound your body makes from glucose and also gets from fruits, beans, grains and nuts. Its main form, myo-inositol, helps cells respond to insulin and other hormone signals, which is why it is studied in polycystic ovary syndrome (PCOS) and pregnancy. It is often called vitamin B8, but it is not a vitamin, because the body produces its own. The research is less settled than the marketing: a 2018 Cochrane review rated the fertility evidence low to very low quality, and the 2023 international PCOS guideline says inositol offers limited clinical benefits and that no specific form or ratio can be recommended. Side effects appear mild, mostly stomach upset at high intakes. Here is what inositol is, what the inositol benefits research actually found, and how to read a label.

Peptide Labs sells a product that lists inositol, but this article does not recommend it. It is general information, not medical advice. PCOS and gestational diabetes are medical diagnoses; if you think either applies to you, see a clinician.

What is inositol?

Chemically, inositol is a ring-shaped carbohydrate, a sugar alcohol. There are nine forms, called stereoisomers. Myo-inositol is by far the most common in the body, and the others are formed from it. Myo-inositol is part of cell membranes and is converted into messenger molecules that relay signals from insulin and several other hormones inside cells.

For a long time inositol was classed as a B vitamin, hence vitamin B8. It lost that status because the body makes it: the kidneys produce most of it from glucose, and the liver and brain make smaller amounts. A 1980 analysis of 487 foods found the most myo-inositol in fruits, beans, grains and nuts, with fresh produce higher than frozen or canned. Cereals, corn, legumes and meat are other sources.

The FDA lists inositol, also called myo-inositol, as generally recognized as safe (GRAS) for use as a nutrient in food, and it may be added to infant formula. Commercial inositol is made from corn by breaking down phytate, a phosphate-rich plant compound that is itself a form of inositol.

Myo-inositol vs D-chiro-inositol

D-chiro-inositol (DCI) is made from myo-inositol through an insulin-dependent process. One theory is that insulin resistance disrupts this conversion in some tissues, which is the reason both forms are studied in PCOS. Many products now pair them in a 40:1 myo-inositol to DCI ratio. That figure is described as matching the ratio found in blood, and its main clinical support is a 2019 Italian trial of 56 women with PCOS that compared seven formulations with just eight women per group. The authors concluded the 40:1 ratio was the most effective for ovulation, but a trial that small cannot settle the question, and the 2023 international guideline states that specific types or combinations of inositol cannot be recommended because quality evidence is lacking.

Inositol benefits: what the research shows

Most inositol benefits research focuses on two areas. Both involve diagnosed conditions, so the summaries below describe what studies found, not what a supplement will do for you.

PCOS research

PCOS is a hormonal condition that a clinician diagnoses, and it is often linked to insulin resistance. A 2018 Cochrane review pooled 13 trials with 1,472 women with PCOS who were trying to conceive, most of them using myo-inositol before IVF. The evidence was rated low to very low quality because of poor reporting and inconsistent results, and the reviewers were uncertain whether myo-inositol improved live birth or pregnancy rates. The authors declared no conflicts of interest.

The 2023 International Evidence-based Guideline for PCOS, developed by an international network of clinicians and patient groups, reached a cautious position. It says inositol in any form could be considered based on personal preferences and values, noting limited harm and possible improvement in metabolic measures, but limited clinical benefit for ovulation, excess hair growth or weight. It says metformin should be considered over inositol for excess hair and central weight, classes inositol as experimental for infertility, and notes that supplement quality and regulation differ from medicines. It also encourages anyone taking inositol to tell their healthcare professional. If you have PCOS symptoms such as irregular periods, see a clinician for diagnosis and a plan; our guide to metformin explains how that prescription medicine is used.

Pregnancy and gestational diabetes research

A 2023 Cochrane review looked at myo-inositol given during pregnancy in seven randomized trials with 1,319 women, six of them in Italy and one in Ireland. Myo-inositol may reduce the rate of gestational diabetes, but the certainty of the evidence was low to very low: the trials were small, used different amounts and timing, and may not apply to other populations. The reviewers called for larger studies that also track possible harms. Pregnancy is not the time to add supplements on your own; ask your obstetric provider.

Blood sugar and cravings

Because myo-inositol is part of insulin signaling, it is sometimes marketed alongside ingredients such as berberine for blood sugar or cravings. Outside the research above, good-quality trials are scarce. Our guides to berberine benefits and how to stop sugar cravings cover approaches with more evidence.

Inositol side effects and safety

Inositol appears well tolerated in studies. A 2011 safety review found that only the highest amount studied caused mild stomach effects such as nausea, gas and diarrhea, and a 2022 review in Open Heart, whose authors disclose ties to companies that sell myo-inositol, describes the same pattern. The 2023 PCOS guideline is more guarded, stating that side effects and safety are not known for inositol as a fertility therapy. Points to keep in mind:

• Pregnancy and breastfeeding: trials exist, but evidence is limited; use only with your provider’s agreement.
• Diabetes or blood sugar medicines: inositol is studied for insulin sensitivity, and interaction data are thin, so tell your clinician before combining it with medicines such as metformin.
• Fertility care: tell your fertility team about every supplement you take.
• Product quality: inositol is sold as a dietary supplement, so amounts and purity are not checked by the FDA before sale. Our guide to third-party tested supplements explains what testing seals cover.

Inositol hexanicotinate is a niacin product

Do not confuse inositol supplements with inositol hexanicotinate, a form of niacin (vitamin B3) often labeled flush free. According to the ODS, niacin absorption from it varies widely and averages about 30% lower than from other niacin forms. It is a niacin supplement, not a source of the inositol studied in the research above.

Reading inositol on supplement labels

Check which form the label names (inositol, myo-inositol or D-chiro-inositol), whether it is the main ingredient or one of many, and whether a ratio is claimed. One product we carry lists inositol:

• JSHealth Detox + Debloat tablets list inositol, without naming the form, alongside taurine, glutamine, glycine, choline, fennel seed, turmeric, milk thistle, dandelion and schisandra. Inositol is one ingredient in a multi-ingredient formula, not a standalone inositol supplement. The label asks people who are pregnant, nursing, under 18, managing a medical condition or taking medication, including the oral contraceptive pill, to consult a physician first.

Frequently Asked Questions

Questions about a label? Contact us or read our Buyer’s Guide. Follow the label and ask a healthcare provider before starting any supplement, especially if you take medicines. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

Last reviewed October 2026.

Related guides: Berberine Benefits: What the Research Shows and What It Does Not, Metformin for Weight Loss: What the Evidence Shows, How to Stop Sugar Cravings: Why They Happen and What Research Supports, Ozempic for PCOS: What the Guideline and Trials Say.