Myo-Inositol: What It Is, Benefits, Dosage and Side Effects

The myo-inositol dosage used in studies is typically about 2 to 4 g per day, often split between morning and evening. Myo-inositol is one of the two main supplement forms of inositol, a sugar-like compound your body makes and gets from fruit, beans and grains. Research on myo-inositol benefits has mostly measured blood sugar and insulin markers, because inositol-based molecules help carry the insulin signal inside cells. Below: what studies measured, food sources, dosage, side effects and sleep.

It is educational, not medical advice.

Key Takeaways

• What it is: inositol is a sugar-like compound your body makes and gets from foods such as fruit, beans and grains. Its main supplement forms are myo-inositol and D-chiro-inositol.
• What it does in cells: inositol-based molecules help carry the insulin signal inside cells, so the body responds to insulin more efficiently.
• What research measured: a meta-analysis of 20 randomized trials (1,239 people) found inositol lowered fasting blood sugar, post-glucose blood sugar and fasting insulin, and improved HOMA-IR (Miñambres et al., 2019). Much of the inositol research has been done in women.
• Amounts used in studies: myo-inositol at about 2 to 4 g a day, often split between morning and evening.
• Side effects: rarely reported in trials and none were serious; mild nausea or gas can show up at higher doses.

What Is Inositol?

Inositol is a sugar-like compound. Your body makes it, and you also get it from foods such as fruit, beans and grains. Because your body produces its own supply, the inositol in food and supplements adds to what is already there rather than being your only source.

Its job is mostly behind the scenes. Inside cells, inositol-based molecules help carry the insulin signal, so the body responds to insulin more efficiently. That role in cell signaling is the reason researchers have studied it mainly for blood sugar and insulin markers.

When people say "inositol" on a supplement label, they nearly always mean one of two forms:

• Myo-inositol: the form behind the 2 to 4 g a day amounts described in studies, and the subject of this guide.
• D-chiro-inositol: the second main supplement form. You will see it on its own or listed next to myo-inositol on some labels.

Myo-Inositol at a Glance

Question	Short answer
What it is	A sugar-like compound the body also makes
Main supplement forms	Myo-inositol and D-chiro-inositol
Role in the body	Helps carry the insulin signal inside cells
Food sources	Fruit, beans and grains
Amounts used in studies	Myo-inositol about 2 to 4 g a day
Side effects reported	Rare in trials; mild nausea or gas at higher doses
Main caution	Glucose-lowering medication

What Research on Inositol Has Measured

When people search for inositol benefits, the research they find is mostly about blood sugar and insulin. That follows from its role in carrying the insulin signal.

The largest summary we draw on is a meta-analysis of 20 randomized trials with 1,239 people. Across those trials, inositol lowered fasting blood sugar, blood sugar after a glucose drink and fasting insulin, and improved HOMA-IR, a marker researchers use to estimate how well the body responds to insulin. These changes were independent of weight change. Side effects were rarely reported and none were serious, though many trials did not track them well (Miñambres et al., 2019).

Much of the research has been done in women with polycystic ovary syndrome (PCOS). A 2024 systematic review prepared for the international PCOS guidelines included 30 trials with 2,230 women. It reported possible benefits for some metabolic measures with myo-inositol or D-chiro-inositol, no clear effect on several other outcomes, and stomach side effects that were typically mild and short-lived (Fitz et al., 2024).

Two points matter when you read findings like these:

• Who was studied: much of the inositol research has been done in women, so results may not apply in the same way to men, to older adults or to people with different health backgrounds.
• What was measured: these are lab markers of blood sugar and insulin, measured over weeks to months. They describe what happened in the trial groups, not what any one person will notice.

Inositol also comes up next to berberine, another ingredient studied for blood sugar. There is no known interaction between the two, and they work in different ways. The one human study that combined them used a five-ingredient product in 148 adults with slightly high fasting blood sugar, so it cannot show how much of the effect came from inositol itself (Derosa et al., 2020). Our guide to berberine and inositol together covers timing and cautions for that pairing.

Inositol Foods

You already get some inositol from everyday food. Fruit, beans and grains are the main food sources, so a diet built around plants supplies a steady amount. Your body also makes inositol on its own, so food is only part of the picture.

The classic measurement comes from a 1980 study that tested 487 foods. The greatest amounts of myo-inositol were in fruits, beans, grains and nuts, and fresh fruits and vegetables held more than frozen, canned or salt-free versions. Using those values, the researchers built diets that supplied anywhere from 225 to 1,500 mg of myo-inositol a day per 1,800 calories (Clements and Darnell, 1980).

That gives a useful sense of scale: a plant-rich diet may supply up to about 1.5 g a day, while the 2 to 4 g amounts used in studies are taken as a supplement powder or capsule, on top of whatever your meals provide.

Inositol and Sleep

Sleep is a newer area of inositol research. In a 2022 randomized, double-blind trial, 60 pregnant women in Iran took 2 g of myo-inositol with folic acid or folic acid alone for 10 weeks, starting in the second trimester. Sleep was measured with the Pittsburgh Sleep Quality Index, and the myo-inositol group ended with better global sleep quality scores, along with better scores for subjective sleep quality, sleep duration and sleep efficiency (Mashayekh-Amiri et al., 2022). It was one small trial in pregnancy, so the results may not apply to other groups, and anyone pregnant should talk with their provider before adding a supplement.

More often, you will see myo-inositol used as one ingredient in evening blends, next to ingredients that have their own sleep research.

Glycine is the best example. In healthy volunteers whose sleep was restricted, 3 g of glycine before bed was followed by less fatigue and better psychomotor vigilance the next day (Bannai et al., 2012). Our guide to glycine for sleep covers that research in detail, and glycine benefits covers the rest of what glycine does.

If you are comparing evening ingredients, our guides to tart cherry for sleep, apigenin and magnesium glycinate for sleep lay out what each one was studied for. For the bigger picture on routines and rest, start with our sleep health hub or our guide to sleep supplements without melatonin. For timing and the amounts used in sleep studies, see our guide to inositol for sleep.

Inositol Dosage Used in Studies

Studies of myo-inositol have typically used about 2 to 4 g a day. A few practical points from how it is usually taken:

• Powder or capsules: myo-inositol powder dissolves easily in water, which makes gram amounts easier to take than a handful of capsules.
• Split doses: many people split it between morning and evening, or take it all at once if that is easier.
• Start one at a time: if you add inositol and another new supplement, start one first for a week or two so you know which one causes any stomach upset.
• Give it time: the trials measured changes over weeks to months, not days.

Myo-Inositol Dosage Per Day at a Glance

Here is how the daily amounts in this guide compare, from food to the highest amount studied:

• From food: diets built from inositol-rich foods supplied about 225 to 1,500 mg of myo-inositol a day per 1,800 calories (Clements and Darnell, 1980).
• Sleep trial in pregnancy: 2 g of myo-inositol a day with folic acid for 10 weeks (Mashayekh-Amiri et al., 2022).
• 40:1 ratio trial in women with PCOS: 2 g of inositols twice a day, 4 g in total, for 3 months (Nordio et al., 2019).
• Highest amount in the safety review: 12 g a day, the only amount that caused mild stomach effects such as nausea, gas and diarrhea (Carlomagno and Unfer, 2011).

Most supplement studies sit in the 2 to 4 g range. Check the grams per serving on the label, since reaching 2 g can take several tablets or capsules.

Your own amount is a question for your healthcare provider, especially if you take medication or have a medical condition.

Myo-Inositol vs D-Chiro-Inositol

Both are forms of inositol, and both appear on supplement labels. Myo-inositol is the form behind the 2 to 4 g a day amounts described above. D-chiro-inositol is the second main form, and some labels list the two together.

You may see combination products that list a 40:1 ratio of myo-inositol to D-chiro-inositol. That number comes from research in women with polycystic ovary syndrome. In one small 2019 trial, 56 women (8 per group) took 2 g of inositols twice a day for 3 months in one of seven formulations, and the authors reported that the 40:1 ratio gave the best results on the hormone and ovulation measures they tracked (Nordio et al., 2019). With groups that small, and a single population, it is a starting point rather than a settled answer. If a product names a ratio, ask your healthcare provider whether it fits what you are looking for.

Inositol Side Effects and Safety

In the trials pooled in the meta-analysis above, side effects were rarely reported and none were serious, though many trials did not track them well (Miñambres et al., 2019). A 2011 safety review found that only the highest amount studied, 12 g a day, caused mild stomach effects such as nausea, gas and diarrhea, and that their severity did not rise with the dose (Carlomagno and Unfer, 2011). The most common complaints are stomach related:

• Stomach effects: mild nausea or gas, mainly at higher doses. Splitting the daily amount may make it easier to take.
• Blood sugar: because inositol is studied for blood sugar, taking it with prescription glucose-lowering medication, or with berberine and that medication, can add up. Talk with your clinician first.

Safety note: if you are pregnant or nursing, under 18, have a medical condition or take any medication, check with your healthcare provider before starting inositol. Evening blends built for sleep can cause drowsiness, so take them at night, not before driving, and avoid combining them with alcohol.

Coming Soon From Synchronicity

Our Melatonin-Free Sleep Powder will have 2,000 mg of myo-inositol in every 9.5 g scoop, alongside magnesium, glycine, tart cherry and apigenin from chamomile flower. It is designed to support restful sleep and help you wind down at night, with no added melatonin and no 5-HTP. Mix 1 scoop in 8 oz of water 30 to 60 minutes before bed. It is not on sale yet. Join the waitlist on the product page to hear when it launches; no payment is taken.

Curious about the magnesium in it? See our magnesium glycerophosphate page, or browse more ingredient guides on our Learn page.

Frequently Asked Questions

What is myo-inositol?

Myo-inositol is one of the two main supplement forms of inositol, a sugar-like compound your body makes and gets from foods such as fruit, beans and grains. Inside cells, inositol-based molecules help carry the insulin signal.

What are the benefits of inositol?

Most research has measured blood sugar and insulin. A meta-analysis of 20 randomized trials found inositol lowered fasting blood sugar and fasting insulin and improved HOMA-IR (Miñambres et al., 2019). Much of that research was done in women, so results may not apply to everyone.

How much myo-inositol is used in studies?

Studies have typically used about 2 to 4 g a day, often split between morning and evening. Ask your healthcare provider what fits you.

What are the side effects of inositol?

In trials, side effects were rarely reported and none were serious. A 2011 safety review found mild nausea, gas or diarrhea only at the highest amount studied, 12 g a day. Check with your clinician first if you take glucose-lowering medication.

Does inositol help you sleep?

Sleep is a newer area of research. In one 2022 trial of 60 pregnant women, those taking 2 g of myo-inositol a day for 10 weeks had better sleep quality scores than those taking folic acid alone. It was a single small trial, so results may not apply to others. Myo-inositol is also used in some melatonin-free evening blends next to glycine and magnesium.

What foods contain inositol?

A 1980 study of 487 foods found the most myo-inositol in fruits, beans, grains and nuts, with fresh produce higher than frozen or canned. Your body also makes inositol, so food is only part of your total.

What is the difference between myo-inositol and D-chiro-inositol?

They are the two main supplement forms of inositol. Myo-inositol is the form behind the 2 to 4 g a day amounts used in studies; some labels list D-chiro-inositol alongside it, often at a 40:1 ratio drawn from research in women with PCOS.

Can I take inositol with berberine?

For most adults, yes. No interaction between them is known, and they work in different ways. Because both are studied for blood sugar, talk with your clinician first if you take glucose-lowering medication. See berberine and inositol together.

When is the best time to take inositol?

No single best time has been set. Many people split it between morning and evening, and it can also be taken all at once. Taking it the same way each day makes it easier to stay consistent.

What are myo-inositol tablets used for?

Myo-inositol tablets, capsules and powders are dietary supplements. The uses researchers have studied most are blood sugar and insulin markers, metabolic and ovulation measures in women with polycystic ovary syndrome (PCOS) and, in one 2022 trial in pregnant women, sleep quality. Studies typically used about 2 to 4 g a day, so check how many grams each tablet supplies, and ask your healthcare provider before using it for a health concern.

Can myo-inositol rich foods give you the amounts used in studies?

Not usually. In a 1980 study of 487 foods, fruits, beans, grains and nuts held the most myo-inositol, and fresh produce held more than frozen or canned. Diets built from those foods supplied about 225 to 1,500 mg a day per 1,800 calories, while studies typically used 2 to 4 g a day as a supplement on top of food.

How long does myo-inositol take to work?

Trials measured changes over weeks to months, not days. The 2022 sleep trial in pregnant women ran for 10 weeks, and the 40:1 ratio trial in women with PCOS ran for 3 months. The blood sugar and insulin trials in the meta-analysis also measured changes over weeks to months, so taking it consistently is what the studies tested.

Is it safe to take myo-inositol every day?

Trials gave myo-inositol daily for weeks to months, and side effects were rarely reported and none were serious. A 2011 safety review found mild nausea, gas or diarrhea only at 12 g a day, the highest amount studied. Check with your healthcare provider first if you are pregnant or nursing, under 18, or take glucose-lowering medication.

Sources

1. Miñambres et al. Meta-analysis of 20 randomized trials of inositol and blood sugar and insulin markers. 2019. PubMed 29980312
2. Derosa et al. Study of a combination product with berberine and inositol in adults with slightly high fasting blood sugar. 2020. PubMed 32184644
3. Clements RS, Darnell B. Myo-inositol content of common foods: development of a high-myo-inositol diet. Am J Clin Nutr. 1980. PubMed 7416064
4. Mashayekh-Amiri S, et al. The impact of myo-inositol supplementation on sleep quality in pregnant women: a randomized, double-blind, placebo-controlled study. J Matern Fetal Neonatal Med. 2022. PubMed 32933356
5. Fitz V, 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. PubMed 38163998
6. Nordio M, Basciani S, Camajani E. The 40:1 myo-inositol/D-chiro-inositol plasma ratio is able to restore ovulation in PCOS patients: comparison with other ratios. Eur Rev Med Pharmacol Sci. 2019. PubMed 31298405
7. Carlomagno G, Unfer V. Inositol safety: clinical evidences. Eur Rev Med Pharmacol Sci. 2011. PubMed 21845803
8. Bannai M, Kawai N, Ono K, Nakahara K, Murakami N. The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers. Front Neurol. 2012;3:61. PubMed 22529837

These statements have not been evaluated by the Food and Drug Administration. This content is for education and is not medical advice. Our products are not intended to diagnose, treat, cure or prevent any disease. Talk with a healthcare provider before starting a new supplement if you are pregnant, breastfeeding or taking medication.