Inositol

Is inositol safe?

Yes, for most adults it is among the safer supplements you can buy. Inositol is a simple carbohydrate the body makes itself and gets from beans, grains, citrus fruit and meat. Supplements usually contain myo-inositol, sometimes mixed with D-chiro-inositol, and are sold mainly to women with polycystic ovary syndrome (PCOS). A 2011 safety review found that only the highest dose studied, 12 g a day, caused side effects, and those were mild: nausea, wind and diarrhoea.

So the real question is not harm but value. The evidence for PCOS is thinner than social media suggests, and some products contain less than they claim.

Does inositol help PCOS?

Possibly a little, and less clearly than its fans say. The most careful assessment is a 2024 systematic review in the Journal of Clinical Endocrinology and Metabolism, written to inform the 2023 international PCOS guideline. It included 30 trials with 2,230 women.

The findings:

• Myo-inositol or D-chiro-inositol may improve some metabolic measures, and D-chiro-inositol may help ovulation.
• On many other outcomes, inositol may have no effect.
• Compared with metformin, inositol was probably no different for fertility outcomes, while metformin did better on waist-hip ratio and excess hair.
• Myo-inositol likely causes fewer stomach side effects than metformin.

The authors' conclusion: evidence for inositol in PCOS "is limited and inconclusive", and women should weigh that uncertainty with their doctor. For a supplement this safe, trying it is a reasonable choice for some. Using it instead of a proper diagnosis and treatment plan is not.

Why inositol is everywhere on TikTok

PCOS is common, diagnosis often takes years, and treatment options are limited, so many women look for answers online. A 2024 study of 238 TikTok videos about PCOS found that inositol was the supplement mentioned most often (26 videos). Most videos were made by people with no health training, and their information scored 1.0 out of 5 on a standard quality scale, against 3.6 for videos by doctors.

The trials do not support inositol as a cure-all for PCOS. A realistic expectation is a modest effect on insulin-related measures in some women.

Inositol in pregnancy

Myo-inositol has been tested to prevent gestational diabetes, mostly in Italy. A 2023 Cochrane review of seven trials (1,319 women) found it may lower the rate of gestational diabetes (risk ratio 0.53) and of high blood pressure in pregnancy, but rated the certainty low to very low. For low blood sugar in newborns, the result was very uncertain, with a confidence interval running from a 10% decrease to a tenfold increase. A larger 2026 meta-analysis of 12 trials (4,765 women) reported a 44% reduction in gestational diabetes and no differences in newborn outcomes.

No signal of harm to babies has emerged, but there are no long-term data on children. Pregnancy decisions should be made with a doctor or midwife, and inositol does not replace glucose screening.

Does the label match the bottle?

Not always. A 2011 Italian study measured myo-inositol in four PCOS products by HPLC. Only one contained more than 95% of the labelled amount, and one had less than 75%.

US recalls are uncommon but real. In 2025 BulkSupplements.com inositol powder was recalled (Class II) because it might contain Staphylococcus aureus bacteria, and in 2021 an inositol product was recalled for undeclared niacin. Separately, openFDA lists dozens of recalls of compounded "lipotropic" weight-loss injections that contain inositol, almost all for lack of sterility assurance. These injections are a different product from oral supplements and carry the risks of any non-sterile injection.

Who should be careful

• People taking metformin, insulin or other diabetes medicines: inositol may add to their effect on blood sugar.
• Pregnant women and those trying to conceive: talk to your doctor or midwife first, and keep taking folic acid as advised.
• Anyone with PCOS who has not been assessed by a doctor: irregular periods have other causes, and PCOS raises the risk of diabetes and heart disease, which need checking.

How to use it more safely

1. Choose plain myo-inositol or a simple myo-inositol and D-chiro-inositol mix from a third-party testedThird-party testingTesting of a supplement by an independent lab to check that it contains what the label says and is free of set contaminants.More in the glossary brand.
2. Stay at 2 to 4 g a day unless your doctor advises otherwise; higher doses add stomach upset without proven benefit.
3. Avoid injections sold for weight loss, which have a long recall record.
4. Give it a fixed trial period with your doctor, such as three to six months, and stop if nothing changes.

How we scored it

Organ toxicity (92) and dose safety (88) are strong: no organ injury reports and only mild stomach effects at high doses. Interactions (85) are few and theoretical. Regulatory actions (85) reflect a legal supplement with a couple of contamination recalls. Product quality (68) is the weakest factor, because tested products often fell short of the label.