The severity of thalassemia is determined by the hemoglobin concentration and hemoglobin content, as well as by the number of red blood cells, the volume of red blood cells, and the morphology of the red blood cells under the microscopic examination of blood smears. Thalassemia is a hereditary hemolytic disease that is characterized by a disorder in the synthesis of the peptide chains of the pearl protein. Thalassemia is mainly manifested by abnormal blood counts, and the severity is mainly related to the following indicators. 1. Red blood cells: patients with thalassemia may have hemolysis, and patients with moderate or severe thalassemia may have a decrease in the number of red blood cells. Patients with moderate or severe thalassemia may have a decrease in red blood cell count, accompanied by an increase in mean red blood cell volume and reticulocyte ratio. For gene carriers and patients with mild disease, the number of red blood cells may be normal. 2. Hemoglobin: patients’ hemoglobin concentration, average hemoglobin content and other indexes may be reduced. Patients with mild thalassemia may have insignificant or no decrease in values, while those with moderate to severe conditions may have a significant decrease in values. 3. Other: thalassemia patients have peptide chain synthesis disorder of pearl protein, which can cause abnormal platelet or white blood cell number in blood routine, and the size and shape of red blood cells may be affected, such as the increase of target-shaped red blood cells in blood smear examination, uneven size of red blood cells, anomalous red blood cells, etc., and red blood cells are typical of the small-cell, hypochromic performance. The severity of thalassemia can also be judged by combining with other indicators, and should also be combined with one’s own symptoms such as anemia, jaundice, hepatosplenomegaly, etc. It is recommended to go to the hospital regularly for review and treatment under the guidance of doctors. In general, thalassemia can be well controlled after treatment.