Inositol is a sugar-like compound. It is a ring of six carbon atoms, each carrying a hydroxyl (OH) group, which makes it a sugar alcohol. The form that matters in food and supplements is myo-inositol, and “inositol” on a label almost always means it. It is a white crystalline powder, about half as sweet as table sugar.
Cells in animals and plants use it to build membrane fats (lipids) and chemical messengers. These messengers pass signals from the cell surface to the inside.
Unlike a vitamin, it is not something you must eat. Reviews say the human body makes up to about 4 g a day from glucose, mostly in the kidneys. A typical Western diet gives about 1 g. Inositol was once counted in the vitamin B family, as “vitamin B8”, until it was clear that the body makes it.
Do not confuse it with phytic acid (IP6, inositol hexaphosphate). That is inositol carrying six phosphate groups, the form in which plants store phosphorus in bran and seeds. It is a different compound.
Here is what most readers do not know. Inositol is sold mainly for polycystic ovary syndrome (PCOS), a common hormone condition in women. Yet the 2023 international PCOS guideline says only that it could be considered, with limited clinical benefit, and calls it experimental for infertility.
And in the youngest premature babies, a large US trial of myo-inositol was stopped early. More infants died on it than on placebo (a dummy treatment).
Health benefits of inositol
Inositol has been tested for more conditions than most supplements, and for none of them is the evidence strong. The best-supported use is PCOS, where pooled trials show more regular cycles and lower insulin and testosterone measures. But an umbrella review found no high-quality evidence, and the 2023 guideline rates the clinical benefit as limited.
For preventing gestational diabetes (diabetes that starts in pregnancy), a Cochrane review found lower rates, with low to very low certainty. A large 2025 trial in women with PCOS found no benefit. Results for depression and panic disorder come from small trials and are mixed. In premature infants, inositol did not help and may have harmed.
Where the dose is given, the PCOS, pregnancy and metabolic syndrome trials below mostly used 2 g of myo-inositol twice a day. That is a supplement dose far above what food gives. A search turned up at least four PCOS inositol trials that were retracted or flagged with an expression of concern, and we left them out.
Here is what 25 studies found, strongest evidence first, including the trials that found nothing.
In PCOS, inositol made regular cycles 1.79 times as likely as placebo
This meta-analysis (a study that pools earlier studies) covered 26 randomized trials with 1,691 women with polycystic ovary syndrome. 806 took inositol, 311 placebo and 509 metformin, and different forms of inositol were pooled. Inositol was not worse than metformin for cycle regularity. Against placebo it lowered BMI (by 0.45), free and total testosterone, androstenedione, glucose and insulin. It raised sex-hormone-binding globulin, and the authors declared no competing interests.
Review of 13 meta-analyses: PCOS gains, but no high-quality evidence
In this review of reviews, inositol improved hormones, insulin resistance and ovulation in PCOS. On the AMSTAR-2 quality tool, 23.1% of the 13 meta-analyses were rated high quality, 53.8% low and 23.1% very low. Of 85 evidence items graded, none was high quality, 18.9% were moderate, 40% low and 41.1% very low. Against placebo or folic acid, insulin resistance (HOMA-IR) fell by 1.14 and ovulation was 2.75 times as likely. Against metformin, most effects were not clear, and the authors say D-chiro-inositol alone should be used with caution; combinations did not consistently beat single forms.
Inositol improved ovulation and cycles in PCOS, but no trial reported births
This meta-analysis covered 10 randomized trials: 362 women on inositol (257 on myo-inositol, 105 on D-chiro-inositol), 179 on placebo and 60 on metformin. Ovulation was 2.3 times as likely and cycle frequency 6.8 times, but the ovulation result varied a lot between trials (I2 = 75%). Only one study each compared pregnancy rates with placebo and with metformin, and none reported live births or miscarriage. The authors call for a well-designed multicenter trial.
Myo-inositol lowered fasting insulin in PCOS, but not clearly testosterone
This meta-analysis covered 9 randomized trials of myo-inositol, alone or with D-chiro-inositol, with 247 women on inositol and 249 controls. Fasting insulin fell (standardized difference -1.02), and so did HOMA-IR, a measure of insulin resistance (-0.59). Testosterone only trended down, androstenedione was unchanged, and sex-hormone-binding globulin rose only in trials of 24 weeks or more. Two authors work for the company Lo.Li. Pharma, and a third was paid as a consultant by it for this analysis.
Show 21 more studies
Inositol plus metformin beat metformin alone for cycles and hirsutism
This meta-analysis pooled 6 randomized trials with 388 women with PCOS, followed for 3 to 6 months. Cycle regularity improved (risk ratio 1.56), and so did the Ferriman-Gallwey score for excess hair growth (hirsutism, -0.97) and the LH/FSH hormone ratio (-0.13). Acne, BMI, fasting glucose and HOMA-IR did not differ clearly. The authors say confidence in the evidence for inositol is limited.
Myo-inositol and metformin did not clearly differ in PCOS
This meta-analysis pooled 8 randomized trials with 1,088 women (460 on metformin, 436 on myo-inositol, 192 on both). The differences in BMI, insulin, glucose and hormones were small and could be chance. They were BMI 0.16, fasting insulin 0.00, fasting glucose 0.11, HOMA 0.09 and LH/FSH 0.20. The authors conclude the two work about equally well, but with no placebo comparison, this cannot show that either beats nothing.
With ICSI, myo-inositol did not clearly improve eggs, embryos or pregnancy
This meta-analysis pooled 8 randomized trials with 1,019 women with PCOS having ICSI, a form of IVF. They took a fertility drug plus inositol or the drug alone. Odds ratios were 2.21 for oocyte (egg) quality, 1.62 for embryo quality and 1.28 for pregnancy rate. All ranges were wide enough to include no effect. The authors say studies of D-chiro-inositol with the right dose, size and duration are still needed.
Myo-inositol in pregnancy may lower gestational diabetes, on low-certainty evidence
This Cochrane review pooled 7 randomized trials with 1,319 women, 10 to 24 weeks pregnant at the start. Six trials were in Italy and one in Ireland. Gestational diabetes may be less common (risk ratio 0.53), with low to very low certainty, and so were hypertensive disorders (0.34) and preterm birth (0.35). Weight gain and caesarean section showed no clear difference. The trials were small and doses and timing varied, so the authors doubt the results apply outside Italy.
Inositol in pregnancy was linked to less preterm delivery in 5 trials
This meta-analysis pooled 5 randomized trials with 965 women; preterm delivery had an odds ratio of 0.35. For gestational diabetes it was 0.49, with a range wide enough to include no effect. Trials used either 2 g of myo-inositol twice daily, or 1,100 mg of myo-inositol plus 27.6 mg of D-chiro-inositol daily. Only the first dose showed a clear effect on gestational diabetes, and no adverse effects were reported.
In pregnant women with PCOS, myo-inositol did not lower complications
This double-blind trial ran at 13 hospitals in the Netherlands, in 464 pregnant women with PCOS. 230 took 2 g of myo-inositol with 0.2 mg of folic acid twice a day, and 234 took folic acid alone. They started at 8 to 16 weeks of pregnancy and continued until delivery. Gestational diabetes, preeclampsia or preterm birth occurred in 25.0% on myo-inositol and 26.8% on placebo: 0.93 times the risk, a gap that could be chance.
In premature infants, inositol did not clearly reduce death or eye damage
This Cochrane review pooled 6 randomized trials with 1,177 infants. Neonatal death fell in 3 older trials (355 infants, risk ratio 0.53). But infant death and retinopathy (eye damage) stage 2 or higher (risk ratio 0.89) did not change clearly, and nor did other complications. In the two high-quality trials of 760 infants under 30 weeks, the larger one was stopped because more infants died in the inositol group. The review advises against routine use, and the authors do not recommend more trials.
In very premature babies, more infants died on myo-inositol (18% against 11%)
This randomized trial ran at 18 US neonatal intensive care centers, supported by the National Institutes of Health. 638 babies born before 28 weeks got 40 mg/kg of myo-inositol every 12 hours or placebo for up to 10 weeks. It did not prevent severe retinopathy, and death or type 1 retinopathy occurred in 29% against 21% (1.41 times the risk). The plan was 1,760 infants, but the trial was stopped early because of a clearly higher death rate on myo-inositol. The authors say the early stop limits firm conclusions, but the results do not support its use in premature infants.
PCOS guideline 2023: inositol could be considered, with limited benefit
This international, evidence-based guideline has 254 recommendations and practice points, built with the GRADE method. It calls inositol experimental for infertility. For inositol in any form it notes limited harm and possible metabolic gains, but limited benefit for ovulation, hirsutism or weight. It prefers metformin for hirsutism and central fat, and says specific types, doses or combinations of inositol cannot be recommended because the evidence is poor.
Cochrane could draw no conclusion on D-chiro-inositol for PCOS
This Cochrane review covered 48 trials with 4,451 women testing insulin-sensitising drugs, 42 of them metformin. Two trials tested D-chiro-inositol against placebo or no treatment, and none reported live births or side effects. Evidence quality across the whole review ranged from very low to moderate.
Myo-inositol cut gestational diabetes from 15.3% to 6% in at-risk women
220 pregnant women with a parent with type 2 diabetes took part. From the end of the first trimester, 110 took 2 g of myo-inositol plus 200 µg of folic acid twice a day. The other 110 took folic acid alone. The trial was open-label (the abstract also calls it placebo-controlled), and the odds ratio was 0.35. Fetal macrosomia (a very large baby) was also lower, and other secondary outcomes did not differ. The next card tested a different dose in a similar group and found no benefit.
An inositol combination did not prevent gestational diabetes in at-risk women
In this randomized trial at one referral center, 240 women with a family history of diabetes took part. Daily, they took 1,100 mg of myo-inositol, 27.6 mg of D-chiro-inositol and 400 µg of folic acid, or folic acid alone. They started at their first antenatal visit. Gestational diabetes occurred in 23.3% on inositol and 18.3% on folic acid alone, a gap that could be chance. Fasting glucose at the glucose tolerance test was 81 mg/dL in both groups.
Myo-inositol for 6 months lowered diastolic pressure, triglycerides and insulin resistance
80 postmenopausal women with metabolic syndrome took 2 g of myo-inositol twice daily (4 g a day) plus diet, or diet plus placebo. On myo-inositol, diastolic pressure (the bottom number) fell 11%, the HOMA index 75% and triglycerides 20%, and HDL (“good”) cholesterol rose 22%. This was a small trial from one research group.
A year of myo-inositol improved every measure except BMI and waist
80 postmenopausal women with metabolic syndrome (40 per group) on a low-energy diet took 4 g of myo-inositol a day or placebo for 12 months. Metabolic syndrome had resolved in 8 women (20%) on myo-inositol and in 1 on placebo. This comes from the same research group, with the same dose and number of women as the card above. The abstract does not say whether it follows the same women.
In PCOS, myo-inositol worked about as well as metformin over 6 months
50 women with PCOS and insulin resistance or high insulin were randomized to metformin (1,500 mg a day) or 4 g of myo-inositol a day. Insulin sensitivity improved and BMI fell in both groups, and cycles became regular in about half of the women. Acne and hirsutism did not change. There was no placebo group.
In premature babies, inositol raised survival without lung disease
221 premature infants with respiratory distress, fed by vein, got 80 mg/kg a day or placebo for their first five days of life. Survival without lung disease was 71% on inositol, against 55% on placebo. Retinopathy of prematurity occurred in 13% on inositol and 26% on placebo, but there was no effect in the 65 infants who also got surfactant. The much larger 2018 trial above, in the youngest infants, found no benefit and more deaths.
In small trials, inositol did not clearly help depression, anxiety or OCD
This meta-analysis pooled seven randomized trials in depression (242 people) and four in anxiety disorders (70 people). There were trends toward more responders in depression and better symptoms in premenstrual dysphoric disorder. Stomach upset was marginally more common on inositol. The authors note the small number of studies.
12 g of inositol a day improved depression scores in 28 patients
In this double-blind trial, 13 people took inositol and 15 a placebo for 4 weeks. The Hamilton Depression Rating Scale improved more on inositol at week 4. Blood counts and kidney and liver tests did not change. The authors say replication is crucial, and the 2014 meta-analysis above found no clear overall effect.
12 g of inositol a day reduced panic attacks in 21 people
In this double-blind, placebo-controlled crossover trial, people with panic disorder took inositol and placebo in turn for 4 weeks. The frequency and severity of panic attacks and the severity of agoraphobia fell more after inositol than after placebo. Side effects were minimal. It was a small, short trial.
In panic disorder, inositol worked about as well as fluvoxamine
20 people with panic disorder took each treatment for one month in this double-blind crossover trial. The doses were inositol up to 18 g a day and the drug fluvoxamine up to 150 mg. Anxiety and agoraphobia scores improved similarly. In the first month, weekly panic attacks fell by 4.0 on inositol and 2.4 on fluvoxamine, a borderline difference. Nausea and tiredness were more common on fluvoxamine, and there was no placebo group.
Added to bipolar drugs, inositol did not beat placebo for depression
In this six-week double-blind trial, 17 people with bipolar depression added inositol or placebo to lithium or valproate. Four of 9 people on inositol met the response definition against none of 8 on placebo, a gap that could be chance. The average change in depression scores did not differ. Response to inositol varied widely between people.
Foods high in inositol
Inositol reaches you in three forms: free myo-inositol, myo-inositol in membrane fats, and phytic acid (IP6) in plants. Animal foods hold mostly the first two, and plant foods hold it mostly as phytic acid. In 1980, Clements and Darnell measured myo-inositol in 487 foods by gas-liquid chromatography.
The most was in fruits, beans, grains and nuts. Fresh fruits and vegetables held more than frozen, canned or salt-free versions. A 2020 review adds that oats and bran hold more myo-inositol than other cereals.
NutriScrolls has no USDA ranking for inositol, and we found no open table of per-food measurements. So the table below holds only the amounts we could source.
An editorial that quotes the 1980 work puts the myo-inositol in an average 2,000 kcal American diet at about 720 mg a day. It gives about 470 mg in a 4 oz serving of grapefruit juice, and its authors are linked to supplement companies. By that arithmetic, the 4 g a day used in the PCOS and metabolic syndrome trials is more than five times an average American diet.
| Food or diet | Myo-inositol, as published | Source |
|---|---|---|
| Grapefruit juice, 4 oz serving | About 470 mg | 2 |
| Average American diet, 2,000 kcal | About 720 mg a day (range 250 to 1,650 mg) | 2 |
| Diets built from the 487 foods measured in 1980 | 225 to 1,500 mg a day per 1,800 kcal | 1 |
| Typical Western diet | About 1 g a day | 3 |
Sources
- Clements RS Jr, Darnell B. Myo-inositol content of common foods: development of a high-myo-inositol diet. Am J Clin Nutr. 1980.
- DiNicolantonio JJ, O’Keefe JH. Myo-inositol for insulin resistance, metabolic syndrome, polycystic ovary syndrome and gestational diabetes. Open Heart. 2022. Editorial; one author is affiliated with companies that sell myo-inositol and the other owns a supplement company. The grapefruit juice and diet figures are quoted from earlier work.
- Dinicola S, Minini M, Unfer V, et al. Nutritional and acquired deficiencies in inositol bioavailability. Correlations with metabolic disorders. Int J Mol Sci. 2017.
- Caputo M, Bona E, Leone I, et al. Inositols and metabolic disorders: from farm to bedside. J Tradit Complement Med. 2020.
How inositol works
Most of what we know about how inositol works comes from cell and lab studies and from reviews of them. Researchers keep coming back to three ideas. Cells use it as a building block for lipids and messengers, and the body makes far more of it than food supplies. Inositol-based messengers also help carry insulin’s signal.
Here is each one, and what has been seen in people.
It is a building block for the cell’s messengers
Inositol is a ring that cells decorate with phosphate groups. Joined to a membrane fat, it forms phosphoinositides. These lipids sit in tiny amounts in membranes, yet help direct traffic and signals inside the cell.
One of them, PIP2, is cut by an enzyme into two pieces. One piece, diacylglycerol, stays in the membrane and switches on protein kinase C. The other, inositol trisphosphate (IP3), moves into the cell and mobilizes calcium. The same ring with six phosphates is phytic acid, the plant compound mentioned at the top.
Simplified drawing of the ring with different numbers of phosphate groups; the exact positions are not shown. Phytic acid in food is a different compound from the myo-inositol in supplements.
How a cell turns an inositol lipid into two signals, as described in cell studies from the 1980s onward. Drawn as a simplified sketch, not to scale.
The body makes more than food gives
Your body builds inositol from glucose, mostly in the kidneys. Reviews put production at up to about 4 g a day, against about 1 g from a typical Western diet. That is why inositol is no longer called a vitamin.
Supplement doses in trials are several times higher than food. The PCOS and metabolic syndrome trials used 4 g a day, and the panic and depression trials 12 to 18 g. One review argues that high blood sugar can lower inositol in tissues. Glucose competes with it for entry into cells and raises its loss in urine.
This is a hypothesis behind the use in insulin resistance, and the trials above are what test it.
Drawn to scale. The food and body figures are estimates quoted in reviews, and estimates of what the body makes vary between sources. Trial doses come from the study cards above.
It may help carry insulin’s message
Some of insulin’s actions are passed on by messengers built on inositol, called inositolphosphoglycans. One kind contains D-chiro-inositol. A small study followed 11 women with PCOS. Those whose release of this messenger rose after a glucose test also became more sensitive to insulin (correlation 0.69).
The study ended early when the supplement ran out, and a correlation does not show that taking inositol causes the change. The authors suggest the messenger may be a target for treatment in PCOS. The human trials are the study cards above.
What has been seen in people
These ideas are plausible, but the results in people are modest and uncertain. In PCOS, 26 pooled trials found more regular cycles and lower insulin and testosterone measures. Yet an umbrella review found no high-quality evidence, and the guideline calls the clinical benefit limited.
In pregnancy, the Cochrane review found fewer cases of gestational diabetes in small, mostly Italian trials. The largest later trial, in women with PCOS, found none. In premature infants, the largest trial found more deaths on inositol. The psychiatric trials were small and used 12 to 18 g a day, and all of these are among the study cards above.
Sources
- Berridge MJ, Irvine RF. Inositol trisphosphate, a novel second messenger in cellular signal transduction. Nature. 1984.
- De Craene JO, Bertazzi DL, Bär S, et al. Phosphoinositides, major actors in membrane trafficking and lipid signaling pathways. Int J Mol Sci. 2017.
- Dinicola S, Minini M, Unfer V, et al. Nutritional and acquired deficiencies in inositol bioavailability. Correlations with metabolic disorders. Int J Mol Sci. 2017.
- Caputo M, Bona E, Leone I, et al. Inositols and metabolic disorders: from farm to bedside. J Tradit Complement Med. 2020.
- Cheang KI, Baillargeon JP, Essah PA, et al. Insulin-stimulated release of D-chiro-inositol-containing inositolphosphoglycan mediator correlates with insulin sensitivity in women with polycystic ovary syndrome. Metabolism. 2008.
- Inositol. Wikipedia (sweetness, appearance, phytic acid).
Is inositol safe? Supplements, dose and interactions
Inositol from food is not a safety concern: people eat roughly 1 g a day and the body makes several grams. We found no upper intake level for inositol from EFSA, the European food safety agency. The EFSA opinions on inositol that we found cover animal feed only. None of the human reviews on this page cites an official upper level either.
- Trial doses. The trials described above mostly used 2 g of myo-inositol twice daily (4 g a day). That ran for 6 to 12 months in the metabolic syndrome trials and until delivery in a pregnancy trial. Psychiatric trials gave 12 to 18 g a day for weeks.
- Side effects. A 2011 safety review found that only the highest dose, 12 g a day, caused mild stomach effects such as nausea, gas and diarrhea. These did not worsen with dose. A co-author of that review is employed by Lo.Li. Pharma, according to later papers. In the psychiatric meta-analysis, stomach upset was marginally more common on inositol than placebo.
- Premature infants. Inositol should not be given to premature infants outside medical care. In the large US trial, 18% of infants on myo-inositol and 11% on placebo died before 55 weeks. The Cochrane review advises against routine use.
- Pregnancy and quality. The Cochrane review of pregnancy trials found no data on long-term outcomes in children and asks future trials to report harms. The 2023 PCOS guideline notes that inositol products can differ in quality and dose, and asks women to tell their health professional. We found no controlled studies of drug interactions.
How to get more inositol
- Best foods. Fruits, beans, grains and nuts had the most among 487 foods measured, and grapefruit juice is quoted at about 470 mg per 4 oz.
- Fresh over processed. In the 1980 measurements, fresh fruits and vegetables held more myo-inositol than frozen, canned or salt-free versions.
- Food versus supplement. A diet gives about 1 g a day, while trials used 4 to 18 g of supplement. We found no trial that compared food with a supplement.
Sources
- Carlomagno G, Unfer V. Inositol safety: clinical evidences. Eur Rev Med Pharmacol Sci. 2011.
- Mukai T, Kishi T, Matsuda Y, et al. A meta-analysis of inositol for depression and anxiety disorders. Hum Psychopharmacol. 2014.
- Phelps DL, Watterberg KL, Nolen TL, et al. Effects of myo-inositol on type 1 retinopathy of prematurity among preterm infants <28 weeks’ gestational age: a randomized clinical trial. JAMA. 2018.
- Howlett A, Ohlsson A, Plakkal N. Inositol in preterm infants at risk for or having respiratory distress syndrome. Cochrane Database Syst Rev. 2019.
- Motuhifonua SK, Lin L, Alsweiler J, et al. Antenatal dietary supplementation with myo-inositol for preventing gestational diabetes. Cochrane Database Syst Rev. 2023.
- Teede HJ, Tay CT, Laven J, et al. Recommendations from the 2023 international evidence-based guideline for the assessment and management of polycystic ovary syndrome. Hum Reprod. 2023.
- Giordano D, Corrado F, Santamaria A, et al. Effects of myo-inositol supplementation in postmenopausal women with metabolic syndrome. Menopause. 2011.
- Santamaria A, Giordano D, Corrado F, et al. One-year effects of myo-inositol supplementation in postmenopausal women with metabolic syndrome. Climacteric. 2012.
- van der Wel AWT, Frank CMC, Bout-Rebel R, et al. Myo-inositol supplementation to prevent pregnancy complications in polycystic ovary syndrome. JAMA. 2025.
- EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP). Scientific opinion on the safety and efficacy of inositol as a feed additive for fish, dogs and cats. EFSA J. 2014.
- Clements RS Jr, Darnell B. Myo-inositol content of common foods: development of a high-myo-inositol diet. Am J Clin Nutr. 1980.
- DiNicolantonio JJ, O’Keefe JH. Myo-inositol for insulin resistance, metabolic syndrome, polycystic ovary syndrome and gestational diabetes. Open Heart. 2022.
- Dinicola S, Minini M, Unfer V, et al. Nutritional and acquired deficiencies in inositol bioavailability. Correlations with metabolic disorders. Int J Mol Sci. 2017.
History of inositol
Myo-inositol was first isolated from muscle extract by J. J. Scherer in 1850. The “myo” in its name is a prefix for muscle. In 1956 Eagle and colleagues reported that normal and cancerous human cells grown in tissue culture need myo-inositol to grow.
A 2017 review says this finding is why inositol was considered, for a while, an essential nutrient in the vitamin B family. It stopped being called a vitamin once it was clear that the liver and kidney make it.
In 1984 Berridge and Irvine described inositol trisphosphate as a new messenger that mobilizes calcium inside cells. Clinical trials followed. A 1992 trial in 221 premature infants with respiratory distress found more survival without lung disease on inositol. In 1995 small trials of 12 g a day reported benefits in depression and panic disorder.
Inositols were later debated as an alternative to metformin for PCOS, because metformin can cause stomach side effects.
The story has since turned more cautious. In 2018 a large US trial in premature infants was stopped early because more infants died on myo-inositol. The 2019 Cochrane review advised against routine use.
In 2023 the international PCOS guideline said inositol offers limited clinical benefit. A 2025 trial in pregnant women with PCOS found no reduction in the combined risk of gestational diabetes, preeclampsia or preterm birth.
Sources
- Inositol. Wikipedia.
- Eagle H, Oyama VI, Levy M, et al. Myo-inositol as an essential growth factor for normal and malignant human cells in tissue culture. Science. 1956.
- Dinicola S, Minini M, Unfer V, et al. Nutritional and acquired deficiencies in inositol bioavailability. Correlations with metabolic disorders. Int J Mol Sci. 2017.
- Berridge MJ, Irvine RF. Inositol trisphosphate, a novel second messenger in cellular signal transduction. Nature. 1984.
- Hallman M, Bry K, Hoppu K, et al. Inositol supplementation in premature infants with respiratory distress syndrome. N Engl J Med. 1992.
- Levine J, Barak Y, Gonzalves M, et al. Double-blind, controlled trial of inositol treatment of depression. Am J Psychiatry. 1995.
- Benjamin J, Levine J, Fux M, et al. Double-blind, placebo-controlled, crossover trial of inositol treatment for panic disorder. Am J Psychiatry. 1995.
- Phelps DL, Watterberg KL, Nolen TL, et al. Effects of myo-inositol on type 1 retinopathy of prematurity among preterm infants <28 weeks’ gestational age. JAMA. 2018.
- Howlett A, Ohlsson A, Plakkal N. Inositol in preterm infants at risk for or having respiratory distress syndrome. Cochrane Database Syst Rev. 2019.
- Teede HJ, Tay CT, Laven J, et al. Recommendations from the 2023 international evidence-based guideline for the assessment and management of polycystic ovary syndrome. Hum Reprod. 2023.
- van der Wel AWT, Frank CMC, Bout-Rebel R, et al. Myo-inositol supplementation to prevent pregnancy complications in polycystic ovary syndrome. JAMA. 2025.
Frequently asked questions about inositol
What does inositol do for the body?
Cells use it to build membrane lipids and chemical messengers, and the body makes up to about 4 g a day. As a supplement, its best-tested use is PCOS. There, 26 pooled trials found more regular cycles (risk ratio 1.79) and lower insulin and testosterone measures. An umbrella review found no high-quality evidence, and results for pregnancy, mood and premature infants are mixed or negative.
Does inositol help with PCOS?
It may help a little, but the evidence is weak. Pooled trials found more regular cycles and better ovulation (risk ratio 2.3 in 10 trials), but none reported live births. The 2023 international guideline says inositol could be considered, with limited clinical benefit. For women having fertility treatment it should be considered experimental, and a meta-analysis of 8 ICSI trials found no gain in pregnancy rate.
Is inositol better than metformin for PCOS?
Not on current evidence. A meta-analysis of 8 trials found no clear difference between myo-inositol and metformin on BMI, insulin or glucose. The guideline prefers metformin for hirsutism and central fat. Metformin causes more stomach side effects, which is why inositol is studied as an alternative. Adding inositol to metformin improved cycle regularity in 6 trials (risk ratio 1.56).
Can inositol prevent gestational diabetes?
Possibly, but it is not proven. A Cochrane review of 7 trials found a lower risk (risk ratio 0.53), with low to very low certainty. Six of the trials were in Italy. A trial in 240 women with a family history of diabetes found no benefit (23.3% against 18.3%). The large 2025 trial in women with PCOS found none either.
How much inositol should you take a day?
No dose is proven best. Most adult trials used 4 g of myo-inositol a day, as 2 g twice daily, and psychiatric trials used 12 to 18 g. The 2023 PCOS guideline says specific types, doses and combinations cannot be recommended for lack of quality evidence. We found no official upper intake level, so ask your clinician before taking more.
Does inositol have side effects?
At 12 g a day or more, mild nausea, gas and diarrhea were reported, and they did not worsen with dose in a 2011 review. The 2023 meta-analysis of 26 PCOS trials called inositol safe. In premature infants, the largest trial found more deaths on myo-inositol (18% against 11%), so it should not be given outside medical care. We found no controlled studies of drug interactions, and no long-term data from pregnancy.
Which foods are high in inositol?
Fruits, beans, grains and nuts had the most among 487 foods measured in 1980, and fresh produce held more than frozen or canned. Grapefruit juice is quoted at about 470 mg per 4 oz, and an average American diet at about 720 mg a day. We found no open table of per-food values, so we cannot rank individual foods.
Is inositol a vitamin, and is it the same as phytic acid?
No to both. Inositol was once called vitamin B8, but the body makes up to about 4 g a day, so it is not an essential nutrient. Phytic acid (IP6) is inositol with six phosphate groups, the plant form found in bran and seeds. It is a related but different compound from the myo-inositol in supplements.