Toxic Dose of Inositol (Myo-Inositol)
The highest safe dose of myo-inositol is 12 grams per day, with doses above this threshold potentially causing mild gastrointestinal side effects such as nausea, flatulence, and diarrhea. 1
Safety Profile of Myo-Inositol
Myo-inositol is a naturally occurring compound belonging to the sugar family that has been used therapeutically for various conditions, particularly polycystic ovary syndrome (PCOS). Research has established the following safety parameters:
- Doses up to 12 g/day are generally well-tolerated with minimal side effects
- Even at the highest studied dose (12 g/day), only mild gastrointestinal symptoms occur
- The severity of side effects does not increase proportionally with dosage 1
- No changes in hematology, kidney, or liver function have been observed at therapeutic doses 2
Therapeutic Dosing vs. Toxic Dosing
Common Therapeutic Doses
- PCOS treatment: 4000 mg/day (2 × 2000 mg myo-inositol + 2 × 200 μg folic acid) 3
- Depression, panic disorder, and OCD: 12 g/day 2
- Attention deficit disorder: 200 mg/kg body weight 2
Signs of Potential Toxicity
While myo-inositol itself has a favorable safety profile, there are important considerations:
- The D-chiro-inositol isomer (a related compound) has shown ovarian toxicity at high doses in animal studies
- In mice, 5 mg/day D-chiro-inositol (human equivalent: 1200 mg/day) altered ovarian histology and increased testosterone levels 4
- Higher doses of D-chiro-inositol (10-20 mg/day in mice, human equivalent: 2400-4800 mg/day) produced ovarian lesions resembling those of aged mice 4
Monitoring for Adverse Effects
When taking myo-inositol, patients should be monitored for:
- Gastrointestinal symptoms: nausea, flatulence, diarrhea
- In specific populations (e.g., PCOS patients), hormonal parameters may be monitored
- No specific laboratory monitoring is required for liver or kidney function based on current evidence 1, 2
Special Populations
Pregnancy
- Myo-inositol has been studied for prevention of neural tube defects, particularly in folate-resistant cases 5
- The recommended dose for neural tube defect prevention is much lower than the potential toxic threshold
Children
- Limited data exists on toxicity in children
- In studies of children with ADHD, doses of 200 mg/kg were used without reports of serious adverse effects 2
Clinical Implications
The wide therapeutic window of myo-inositol makes it a relatively safe supplement, with the primary concern being mild gastrointestinal discomfort at doses of 12 g/day or higher. However, caution should be exercised when using high doses of D-chiro-inositol, particularly in women with PCOS, as animal studies suggest potential ovarian toxicity.