After electrophoresis of normal human hemoglobin, four bands are shown on the electrophoretic spectrum. The one closest to the positive pole is hemoglobin A, the most dominant hemoglobin, which accounts for more than 95% of adult hemoglobin. It is followed by hemoglobin A2, which accounts for 2-3% of all hemoglobin in normal people. The latter two are very small in amount and are non-hemoglobin components within the red blood cells. The presence of elevated hemoglobin A2 in hemoglobin electrophoresis is an important basis for the diagnosis of β-thalassemia. This is because in β-thalassemia, there is a significant increase in hemoglobin A2, but in the case of megaloblastic anemia caused by folic acid deficiency, a mild increase in hemoglobin A2 may also occur. The most common disorder in which hemoglobin A2 is reduced is iron deficiency anemia.