The amount of nutrients in this product is relatively nontoxic and is usually well tolerated. However, undesirable effects may occur, particularly when the nutrients are used at high doses (e.g., concomitant use of other multivitamin-mineral supplements), see also Overdosage.
Iron: The most common undesirable effects of iron are gastrointestinal (GI) problems, including nausea, vomiting, bloating, abdominal discomfort/epigastric pain, black stools, diarrhea, constipation and anorexia.
Nervous system disorders: Metallic taste.
Gastrointestinal disorders: flatulence, gastrointestinal irritation, heartburn, stomach discomfort.
Injury, poisoning and procedural complications: Long-term administration of large amounts of iron may cause hemosiderosis clinically resembling hemochromatosis, which is a genetic condition characterized by excessive iron absorption, excess tissue iron stores, and potential tissue injury.
Vitamin B6: Although vitamin B6 is generally considered to be relatively nontoxic, adverse neurologic effects have been reported following chronic administration of large pyridoxine dosages, e.g., more than 200 mg daily.
Psychiatric disorders: Sleepiness.
Nervous system disorders: Headache, paresthesia (tingling, prickling, or burning sensation).
Gastrointestinal disorders: Nausea.
Investigations: Decreased serum folic acid concentrations, increased serum aspartate aminotransferase (AST, a liver enzyme).