Normal values for reticulocytes are divided into two types, with normal reference values of 0.5%-2.0% for adults and 2.0%-6% for newborns. Reticulocytes are a stage in the development of erythrocytes. The proliferation and development of the erythrocyte system in the bone marrow proceeds from stem cells to primitive erythrocytes, then to early juvenile erythrocytes, middle juvenile erythrocytes, late juvenile erythrocytes, reticulocytes, and then to mature erythrocytes. From primitive erythrocyte proliferation to the late juvenile erythrocyte stage, it takes about 72 hours to divide 3-4 times. The nucleus becomes larger and smaller, and the cytoplasm gradually increases in hemoglobin. After the late juvenile erythrocytes, the cells no longer divide, and the nucleus is discharged during development and becomes reticulocytes, which contain a small amount of RNA, and become reticulocytes when stained with brilliant tar blue. Reticulocytes further mature RNA disappears and become mature erythrocytes. It takes about 48 hours to develop from late juvenile erythrocytes to mature erythrocytes, and the life span of mature erythrocytes is about 120 days. Under normal conditions, nucleated red blood cells in the bone marrow are not released into the blood circulation, only reticulocytes and mature red blood cells are released into the blood. Therefore, checking the reticulocyte count of peripheral blood can be used to infer the status of bone marrow-derived erythrocytes. In the past, counting reticulocytes was cumbersome and time-consuming, but now the average volume and pressure of some reticulocytes can be measured with a device. The reticulocytes in normal peripheral blood are relatively small and are now used clinically to determine the hematopoietic status of the bone marrow erythrocyte system. Increased reticulocytes are mostly seen in the significant increase of heavy metal poisoning, hemolytic anemia, megaloblastic anemia, pernicious tumors, recovery from bone marrow suppression can increase; decreased reticulocytes are seen in decreased erythropoiesis, aplastic anemia, etc.