Myo-Inositol: Evidence-Based Support for Women with PCOS and Insulin Resistance

An important update: On 12 May 2026, an international consensus published in The Lancet renamed Polycystic Ovary Syndrome (PCOS) to Polyendocrine Metabolic Ovarian Syndrome (PMOS). The research on myo-inositol discussed in this article was conducted under the PCOS designation. The condition is the same and the findings remain relevant. Both names will be used during the transition to the 2028 ICD update. Read our explainer on what the rename means for your hormones and fertility.

Myo-inositol is a naturally occurring cyclic carbohydrate, once thought to be vitamin B8. Although not considered essential, it plays a key role in glucose metabolism and is produced endogenously, particularly by the kidneys. It is found in high concentrations in tissues that utilise large amounts of glucose such as the brain, heart, and ovaries.^[1][2][3][7]

The demand for myo-inositol increases with age, high sugar intake, sodium deficiency, insulin resistance, antibiotic use, and conditions like type 1 and type 2 diabetes.^[5][6] Folate, on the other hand, is critical for DNA synthesis and repair, and plays a synergistic role in reproductive health.

Myo-inositol and PCOS (PMOS)

Insulin resistance is present in 70 to 80% of women with PCOS (PMOS) and central obesity and 15 to 20% of lean PCOS patients.^[8] Hyperinsulinemia contributes to androgen excess and disrupted ovulation through elevated LH secretion. Myo-inositol has shown positive effects in modulating these mechanisms:

• In a 12-week RCT, 2g of myo-inositol (plus 200mcg folate) significantly reduced LH, prolactin, testosterone, insulin, and the LH:FSH ratio, while restoring menstrual cycles in amenorrheic and oligomenorrheic women.^[9]
• Another study found 2g per day improved ovulation, insulin resistance, and reduced BMI in anovulatory PCOS patients. 61.7% ovulated with myo-inositol, and 72.2% with added clomiphene.^[10]

Myo-inositol vs metformin

Although metformin is a common treatment for PCOS (PMOS), studies show that myo-inositol is better tolerated with fewer side effects, while still offering metabolic and reproductive benefits.^[11]

IVF support beyond PCOS (PMOS)

A systematic review found that myo-inositol supplementation reduced gonadotropin requirements in both PCOS and non-PCOS women undergoing IVF. It also significantly shortened ovarian stimulation in the PCOS group.^[12]

In PCOS (PMOS) patients, an imbalance between myo-inositol and D-chiro-inositol (DCI) in the ovaries contributes to dysfunction. High conversion of myo-inositol to DCI may reduce oocyte quality and follicular function.^[13]

Gestational diabetes prevention

Two separate trials demonstrated that taking 2g of myo-inositol twice daily reduced the incidence of gestational diabetes by 65 to 87.3% in high-risk pregnancies.^[12][13]

Myo-inositol combined with folate supports insulin sensitivity, hormonal balance, ovulation, and pregnancy outcomes in women with PCOS (PMOS) and insulin resistance. It also offers added benefits for IVF patients and in gestational diabetes prevention.

Further reading on PCOS (PMOS)

For more on the nutrients and lifestyle approaches discussed in this article:

• The benefits of inositol for fertility — a broader look at how inositol supports reproductive health beyond PCOS
• Folate, vitamin D and PCOS (PMOS) — why bioavailable folate matters for women with PCOS
• NAC and PCOS (PMOS) — the evidence for N-Acetyl Cysteine alongside inositol for insulin sensitivity
• PCOS (PMOS) and egg quality — how the condition may affect egg development and what the research suggests
• Luteal phase defects and PCOS (PMOS) — how PCOS may affect the second half of your cycle
• PCOS has been renamed PMOS — what the new name means for your hormones and fertility

References

1. Bizzarri M et al. (2016). Expert Opin Drug Metab Toxicol;12:1181–96.
2. Corrado F, Santamaria A. (2015). In: Watson RR, Dokken BB. Glucose intake and utilisation. Boston: Academic Press.
3. Chu SH, Hegsted DM. (1980). J Nutr;110:1217–23.
4. De Grazia S et al. (2012). Expert Opin Drug Deliv;9:1033–9.
5. Daughaday WH, Larner J. (1954). J Clin Invest;33:326–32.
6. Dinicola S et al. (2017). Int J Mol Sci;18(10).
7. Artini PG et al. (2013). Gynecol Endocrinol;29:375–9.
8. Kamenov Z et al. (2015). Gynecol Endocrinol;31:131–5.
9. Facchinetti F et al. (2019). Gynecol Endocrinol;35:198–206.
10. Laganà AS et al. (2018). Arch Gynecol Obstet;298:675–84.
11. Unfer V et al. (2014). Reprod Sci;21:854–8.
12. D'Anna R et al. (2013). Diabetes Care;36:854–7.
13. Matarrelli B et al. (2013). J Matern Fetal Neonatal Med;26:967–72.

External references: NHS: Polycystic ovary syndrome (PCOS)  |  The Lancet: PMOS consensus 2026

This content is for educational purposes only and is not intended to diagnose, treat, or replace medical advice. Always consult your healthcare provider before starting any new supplement.