Myo-inositol is a six carbon cyclitol that contains five equatorial and one axial hydroxyl groups. Myo-inositol has been classified as an insulin sensitizing agent and it is commonly used in the treatment of the Polycystic Ovary Syndrome (PCOS). However, despite its wide clinical use, there is still scarce information on the myo-inositol safety and/or side effects. The aim of the present review was to summarize and discuss available data on the myo-inositol safety both in non-clinical and clinical settings. The main outcome was that only the highest dose of myo-inositol (12 g/day) induced mild gastrointestinal side effects such as nausea, flatus and diarrhea. The severity of side effects did not increase with the dosage.