Currently, there are many iron preparations available containing different types of iron salts, including ferrous sulfate, ferrous fumarate, ferrous ascorbate but common adverse drug reactions found with these preparations are mainly gastrointestinal intolerance like nausea, vomiting, constipation, diarrhea, abdominal pain, while ferrous bis-glycinate (fully reacted chelated amino acid form of iron) rarely make complication.