The different forms of iron in supplements contain varying amounts of elemental iron. (ods.od.nih.gov)
Taking supplements containing 25 mg of elemental iron, particularly on an empty stomach, can cause nausea and constipation and reduce zinc absorption. (globalhealingcenter.com)
Women should therefore consult with a physician before supplementing, and stay within a low dosing range, about 25 - mg of elemental iron taken several times daily. (appliedhealth.com)