Anemia is defined as a significant reduction in the mass of circulating red blood cells or the concentration of hemoglobin. Nowadays, we mostly use automated instruments to count the red blood cells and hemoglobin in the peripheral blood. The normal values slightly vary with the age of the individual, with gender and location (especially the altitude above sea level). In general, normal levels is shown in Table 6.1. At present, domestic standard for the diagnosis of anemia is as follows, in adults, Males: Hb < 120 g/L, Females: Hb < 110 g/L, Pregnancy: Hb < 100 g/L. But China is a country with vast expanse of territory, the normal ranges for these values can be slightly varied in different areas.