Inositol (Myo-Inositol): Uses, Benefits, Dosage & Safety

Last updated: June 2026 · Reviewed by the FactoWiki Editorial Team for clarity and source accuracy

Quick summary

Inositol is a vitamin-like compound with its best evidence in polycystic ovary syndrome (PCOS), where myo-inositol may improve insulin sensitivity and ovulation. It's also studied, at high doses, for anxiety.

What is Inositol (Myo-Inositol)?

Inositol is a naturally occurring sugar-like compound, sometimes loosely called 'vitamin B8', that the body makes and gets from foods like fruit, beans and grains. The most-used forms are myo-inositol and D-chiro-inositol. It plays a role in how cells respond to insulin and in neurotransmitter signalling. It is marketed mainly for PCOS, fertility, mood and metabolic support — and among these, the PCOS evidence is the strongest.

What Inositol (Myo-Inositol) is commonly used for

Inositol (Myo-Inositol) is used in supplements as nutritional support, not as a treatment for any medical condition.

How Inositol (Myo-Inositol) works

Inositol acts as a 'second messenger' that helps relay the signal from insulin and certain neurotransmitters inside cells. In PCOS, which often involves insulin resistance, myo-inositol is thought to improve insulin sensitivity, which can in turn support more regular ovulation and hormonal balance. Its role in serotonin and other signalling underlies the interest in anxiety, where high doses have been studied.

What the evidence says

Here's an honest snapshot of what published research suggests about Inositol (Myo-Inositol) — including where the evidence is limited.

Trials and reviews suggest myo-inositol may improve insulin sensitivity, menstrual regularity and ovulation in women with PCOS. (PubMed research)
Some small studies suggest high-dose inositol may help anxiety and related conditions, with limited evidence. (PubMed research)
It is generally combined or compared with the D-chiro-inositol form, often in a physiological ratio. (PubMed research)

Typical dosage used in studies

PCOS studies commonly use about 2-4 g/day of myo-inositol (sometimes with a small amount of D-chiro-inositol); anxiety studies have used higher amounts. This is research information, not a recommendation.

Side effects and safety

Inositol is generally very well tolerated; mild digestive upset (nausea, gas) can occur at higher doses. It has a good safety record overall.

Medication interactions and who should avoid Inositol (Myo-Inositol)

Medication & safety check

People who are pregnant or managing a medical condition such as PCOS should use it under medical guidance so it fits with the rest of their care. Those on diabetes medication should be aware of possible additive effects on blood sugar.

This is general information, not personal medical advice. If you take any medication, confirm it's safe to combine with Inositol (Myo-Inositol) with your doctor or pharmacist first.

Sources & further reading

The evidence summary above is drawn from these sources. For general, authoritative background you can also consult:

Frequently asked questions

What is inositol best for?

Its strongest evidence is in PCOS, where myo-inositol may improve insulin sensitivity, menstrual regularity and ovulation.

Does inositol help anxiety?

Some small studies suggest high-dose inositol may help, but the evidence is limited.

Myo-inositol or D-chiro-inositol?

Myo-inositol is the most-studied; the two are often combined, sometimes in a set ratio. PCOS care should be guided by a doctor.

What dose is used for PCOS?

Around 2-4 g/day of myo-inositol in studies, often with a small amount of D-chiro-inositol.

Is inositol safe?

Yes, generally very well tolerated, with mild digestive effects at higher doses.