Anemia is the most common blood disorder and is usually a result of iron deficiency. In essence, it is a decreased ability of the red blood cells to provide adequate oxygen supplies to body tissues. Symptoms of anemia include weakness, heart palpitations, lassitude, light-headedness, fatigue and—sometimes—subtle behavioral changes.

Events that trigger iron deficiency include growth spurts during childhood, pregnancy and a diet poor in animal proteins. Additionally, certain medications result in anemia, as does external or internal blood loss or infection. Inherited disorders that affect the production and function of red blood cells or hemoglobin (a pigment that gives oxygen to tissues and carries away carbon dioxide) also play a role. Many gastrointestinal surgical procedures, as well as chronic diarrhea, can trigger the condition. The elderly, adults who take aspirin on a daily basis (which can cause bleeding in the GI tract), and volunteer blood donors also are at risk. Often, iron-providing dietary supplements irritate the stomach.