Erythrocyte volume distribution width is an index that can reflect the degree of uniformity of red blood cell volume size. The reference range of normal value is generally <14.9%, and it has certain clinical significance for the diagnosis and differential diagnosis of anemia when analyzed together with other test results. If the erythrocyte volume distribution width is low, it can generally indicate that the erythrocyte size is relatively uniform, but it cannot indicate any disease. If the red blood cell volume distribution width is only slightly low, and the other indicators of blood routine are within the normal range, it is a normal phenomenon and can continue to be observed without special treatment. However, if the average red blood cell volume is small, iron deficiency anemia or thalassemia may be present; if the average red blood cell volume is large, megaloblastic anemia may be present. In this case, it is necessary to go to the hematology department for further tests to clarify the type and cause of the anemia and then correct it. Usually, a single physical examination indicator may not indicate the type and direction of the disease, and several indicators need to be combined in order to determine the disease. The width of the red blood cell volume distribution can be analyzed in combination with the hematocrit. If both appear to be increased, it suggests a possible myelodysplastic syndrome, megaloblastic anemia, etc. If the erythrocyte volume distribution width is high and the hematocrit is normal, there may be aplastic anemia, paroxysmal sleep hemoglobinuria, or G6PD deficiency; if the erythrocyte volume distribution width is increased and the hematocrit is decreased, there may be iron deficiency anemia. For patients with iron deficiency anemia, they can be treated by iron supplementation. While patients with mild thalassemia usually do not need treatment, patients with severe disease need medication and blood transfusion, and children may need hematopoietic stem cell transplantation.