Recently, myo-inositol supplementation has gained momentum in the management of PCOS patients, due to its evidence base and the absence of side effects (16).

What is Myo-Inositol?

Myo-Inositol is one of nine different forms of inositol. It is a naturally occurring sugar alcohol found in dietary sources such as fruits, vegetables, nuts and cereals (17,18). myo-inositol acts as an intracellular messenger to regulate several hormones including thyroid-stimulating hormone (TSH), follicle-stimulating hormone (FSH) and insulin (17).

How does Myo-Inositol help people with PCOS?

There is much interest in the role of myo-inositol in the management of people living with PCOS. Emerging data from small studies is promising, however further large-scale studies are needed. Table 2 provides an overview of the clinical benefits of myo-inositol in people living with PCOS.

Table 2: Benefits of Myo-Inositol in patients with PCOS

Clinical Feature

Potential Benefit of myo-inositol

Insulin Resistance

Myo-inositol has been found to mediate the post-receptor effects of insulin-modifying intracellular metabolism and inhibits duodenal glucose absorption, helping to decrease blood glucose levels (19). A recent meta-analysis demonstrated a significant decrease in fasting insulin in PCOS patients who received myo-inositol compared to other treatments (17). Although findings are limited by inconsistent definitions of PCOS and confounding factors e.g., dose and duration. A systematic review of six RCTs comparing treatment with metformin vs. myo-inositol in people with PCOS found no difference in the short-term effect on fasting insulin, Homeostatic Model Assessment for Insulin Resistance (HOMA) index, testosterone, androstenedione, SHBG and BMI. Additionally, there was an absence of adverse reactions in patients treated with myo-inositol (20).


Myo-inositol reduces leptin secretion and therefore may promote weight loss (21). Small trials have shown a small amount of weight loss in patients taking myo-inositol supplements. However, myo-inositol has not been found to cause weight loss in people with a BMI > 40kg/m2 (21).


Clinical trials show promising results:

- An RCT (137 people with PCOS/IR) found those treated with myo-inositol were six times as likely to report regular menstrual cycles as compared to placebo groups (22).

- An RCT found that myo-inositol supplementation induced menstrual cycle regularity in 75 (53.6%) PCOS patients after 6 months. Ovulation occurred in 101 (72.1%) cases after 6 months of myo-inositol treatment (23)..

- A meta-analysis in anovulatory women with PCOS found that treatment with inositol significantly increased the ovulation rate (RR 2.3; 95% CI 1.1–4.7; I 2 = 75%) compared with placebo (n=257 participants) (24).

Oocyte Quality

Myo-inositol has been associated with decreased oestradiol levels on the day of ovulation, which increased the number of large follicles without increasing the total number of oocytes. This reduced the risk of ovarian hyperstimulation and in turn improved oocyte quality (19). A recent study examined the effects of myo-inositol and folic acid in 50 women with PCOS undergoing assisted reproductive technology. The fertilisation rate and embryo quality significantly improved in the study group, but the number of retrieved oocytes were not statistically different between groups (25). A 2017 systematic review concluded that myo-inositol was insufficient at improving oocyte quality. Future studies are needed to examine appropriate dose, and duration of myo-inositol to clarify its role in the management of fertility and PCOS (26).

Gestational Diabetes Mellitus (GDM)

Existing results of antenatal myo-inositol supplementation are promising. A systematic review found that myo-inositol reduced fasting blood glucose and one‐hour postprandial blood glucose by an average of 0.47 mmol/L and 0.90 mmol/L respectively in people with GDM (18). A Cochrane review found that antenatal supplementation of myo-inositol did not impact on other outcomes such as the risk of having a caesarean section, a large baby, obstructed labour or a baby with low blood glucose levels. Further studies are needed to assess the maternal and infant outcomes of myo-inositol during pregnancy (27).


A small study (n=26) provided people with mild and moderate hirsutism with 2g myo-inositol bi-daily for 6 months. This led to a significant decrease in the levels of total androgens and severity of hirsutism (28). The data is promising, but further large-scale studies are needed.



More studies are needed to investigate effects of myo-inositol on acne. However, small trials have shown promising results.

- A prospective study evaluated myo-inositol 2g plus folic acid 200µg twice daily for 6 months to treat acne in 38 patients with PCOS. Improvement in acne was reported and the acne had disappeared in 53% of patients (29).

- An RCT (n=50) patients with PCOS and acne showed papulopustular lesions were reduced and inflammation was eliminated when given 2g of inositol, twice daily, for 6 months (30).