Should you take a IRON supplement? Low iron, also known as iron deficiency, can be caused by a variety of factors, including: 1. Inadequate dietary intake of iron: Iron is found in red meat, poultry, seafood, beans, lentils, spinach, and fortified cereals. If you don't consume enough of these foods, you may not be getting enough iron. 2. Poor absorption of iron: Certain medical conditions, such as celiac disease, inflammatory bowel disease, and gastric bypass surgery, can interfere with the body