Inositol
Inositol appears low-risk at the doses studied and has moderate evidence for lowering the chance of gestational diabetes, but for PCOS, the use it is mostly sold for, the 2023 international guideline found only limited clinical benefit and says no particular type, dose or ratio can be recommended.
Small trials from the 1990s at 12 to 18 g a day suggest it may ease panic disorder, but a review pooling the depression and anxiety trials found no clear effect. The main caution is pregnancy: the gestational diabetes trials were in pregnant women, but ask your midwife or doctor first; very high doses can upset the stomach.
At a glance
Last reviewed 10 October 2026What it's used for
Evidence is rated per use. The same ingredient can be strong for one thing and traditional for another.
| Use | Evidence | What the research shows |
|---|---|---|
| Preventing gestational diabetesCompare remedies for blood sugar → | Moderate | A 2023 Cochrane review of 7 trials (1,319 women, six in Italy, one in Ireland) found myo-inositol may cut gestational diabetes (risk ratio 0.53), but rated the evidence low to very low certainty and said there is not yet enough to support routine use. A 2026 meta-analysis of 12 trials (4,765 women) found a 44% lower risk. In one Italian trial of women with a parent with type 2 diabetes, 2 g twice daily cut gestational diabetes from 15.3% to 6%.3,4,5 |
| PCOS: insulin resistance and hormone levelsCompare remedies for women’s health → | Limited | A 2024 review of 30 trials, done for the international PCOS guideline, found myo-inositol plus folic acid lowered fasting insulin and insulin resistance (HOMA-IR) against folic acid alone in 2 small trials (very low certainty), and D-chiro-inositol lowered free testosterone in 2 trials of 64 women. Against metformin there was no difference in blood sugar or insulin measures, and metformin did better for waist-to-hip ratio and excess hair. The guideline says inositol could be considered for its potential metabolic benefit, but with limited clinical benefit.1,2 |
| PCOS: irregular periods and ovulation | Limited | In the guideline's review, D-chiro-inositol (600–1,200 mg) raised ovulation rates against placebo in 2 small trials (64 women, low certainty), but myo-inositol did no better than folic acid alone for ovulation and no better than metformin for restoring regular periods or ovulation. An earlier review that did find more regular cycles included trials the guideline team excluded over research-integrity concerns. For infertility the guideline calls inositol experimental.1,2 |
| Panic disorderCompare remedies for stress and anxiety → | Limited | In a 1995 crossover trial of 21 people, 12 g a day for 4 weeks cut the number and severity of panic attacks more than placebo. In a 2001 crossover trial of 20 people, up to 18 g a day did as well as the antidepressant fluvoxamine. But a 2014 meta-analysis pooling 4 small anxiety-disorder trials (70 people) found no significant effect on anxiety symptoms.6,7,8 |
| Depression | Limited | A 2014 meta-analysis of 7 placebo-controlled trials (242 people, including bipolar depression and premenstrual dysphoric disorder) found no significant effect on depressive symptoms. There were slightly more responders on inositol (p = 0.06) and a trend towards benefit in premenstrual dysphoric disorder (p = 0.07), but the trials were few and small.8 |
| Obsessive-compulsive disorder | Limited | The same 2014 meta-analysis included 2 small obsessive-compulsive disorder trials and found no significant effect on obsessive-compulsive symptoms when they were pooled.8 |
How much
Ranges below are what studies used and what supplements commonly contain. They are not a recommendation for you. Start at the low end.
How people take it
Safety
Who should avoid
- Pregnancy — trials used it, but ask your midwife or doctor before starting
- Trying to conceive with PCOS — the guideline calls it experimental for fertility
- Taking lithium or valproate — they act partly by lowering inositol; ask first
- Sensitive stomach — high doses (about 12 g a day) can cause nausea and diarrhoea
Known interactions
Questions people ask
Does inositol work for PCOS?
Only modestly, on current evidence. The review done for the 2023 international PCOS guideline found some improvement in insulin and hormone measures but no clear benefit for weight, periods or pregnancy, and judged the evidence limited and inconclusive.
The guideline says inositol could be considered as a personal choice, noting limited harm and limited clinical benefit.
Is the 40:1 myo-inositol to D-chiro-inositol ratio better?
Not proven. The 40:1 ratio is said to match the body's natural balance, and it reversed PCOS features in mice, but the only human trial comparing ratios had 8 women per group and its evidence was rated very low certainty. The 2023 guideline says no specific type, dose or combination of inositol can currently be recommended.
Is inositol safe in pregnancy?
The gestational diabetes trials gave it to pregnant women, and the five that reported on it found no side effects in the mothers, but the trials were small and did not track longer-term outcomes for babies. The PCOS guideline says its side effects and safety are not known in the fertility setting. Ask your midwife or doctor before taking it.
Can inositol replace metformin for PCOS?
The guideline advises metformin over inositol for excess hair and fat around the waist, although inositol causes fewer stomach side effects. Trials found little difference between them for blood sugar measures, periods or ovulation. Talk to your doctor before changing any prescribed treatment.
Sources (10)
- Clinical guideline Teede HJ, Tay CT, Laven JJE, et al. Recommendations From the 2023 International Evidence-based Guideline for the Assessment and Management of Polycystic Ovary Syndrome. J Clin Endocrinol Metab. 2023.
- Systematic review and meta-analysis Fitz V, Graca S, Mahalingaiah S, et al. Inositol for Polycystic Ovary Syndrome: A Systematic Review and Meta-analysis to Inform the 2023 Update of the International Evidence-based PCOS Guidelines. J Clin Endocrinol Metab. 2024.
- Cochrane systematic review Motuhifonua SK, Lin L, Alsweiler J, Crawford TJ, Crowther CA. Antenatal dietary supplementation with myo-inositol for preventing gestational diabetes. Cochrane Database Syst Rev. 2023.
- Systematic review and meta-analysis Poyatos-León R, Martínez-Vizcaíno V, Sequí-Domínguez I, et al. The effect of myo-inositol supplementation on gestational diabetes mellitus prevention: a systematic review and meta-analysis. Am J Obstet Gynecol. 2026.
- Randomised controlled trial D'Anna R, Scilipoti A, Giordano D, et al. myo-Inositol supplementation and onset of gestational diabetes mellitus in pregnant women with a family history of type 2 diabetes: a prospective, randomized, placebo-controlled study. Diabetes Care. 2013.
- Randomised crossover trial Benjamin J, Levine J, Fux M, Aviv A, Levy D, Belmaker RH. Double-blind, placebo-controlled, crossover trial of inositol treatment for panic disorder. Am J Psychiatry. 1995.
- Randomised crossover trial Palatnik A, Frolov K, Fux M, Benjamin J. Double-blind, controlled, crossover trial of inositol versus fluvoxamine for the treatment of panic disorder. J Clin Psychopharmacol. 2001.
- Meta-analysis Mukai T, Kishi T, Matsuda Y, Iwata N. A meta-analysis of inositol for depression and anxiety disorders. Hum Psychopharmacol. 2014.
- Review Carlomagno G, Unfer V. Inositol safety: clinical evidences. Eur Rev Med Pharmacol Sci. 2011.
- Uncontrolled pilot study Cantelmi T, Lepore E, Unfer VR, Unfer V. Safety of inositol supplementation in patients taking lithium or valproic acid: a pilot clinical study. Eur Rev Med Pharmacol Sci. 2022.
Last reviewed 10 October 2026 · Next review April 2027 · How we rate evidence
Reader notes
Experiences and questions from readers, read by an editor before they appear. They are personal accounts, not evidence, and are not medical advice.