An insufficient amount of iron may be present in the body due to a combination of several different causes. These variables include: The most common cause is bleeding in the intestines and stomach, and both men and women who have been through menopause are at an increased risk for developing this condition. This disorder may be brought on by an ulcer in the stomach, cancer of the stomach, cancer of the intestine, or the use of non-steroidal anti-inflammatory medications, sometimes known as NSAIDs.