Toxicity has not been reported, although people with chronic renal failure show elevated levels and should not take inositol, except under medical supervision.
Large amounts of phytate, the common dietary form of inositol, reduce the absorption of calcium, iron, and zinc. However, supplemental inositol does not have this effect.
One review article suggested that inositol may stimulate uterine contractions.5 While no research has demonstrated that inositol actually has this effect, women who are or could become pregnant should consult a doctor before taking inositol.