The average life span of a normal human red blood cell is 120 days. Red blood cells are the most numerous blood cells in the blood. Normal adults produce about 2 x 10^11 red blood cells per day, and the bone marrow is the only place where red blood cells are produced. The hematopoietic cells in the red bone marrow undergo several steps of differentiation and eventually form mature red blood cells. Red blood cells are destroyed and renewed every day. About 0.8% of senescent red blood cells are destroyed every day, and 90% of senescent red blood cells are engulfed by macrophages. The presence of hypersplenism can cause anemia due to excessive red blood cell destruction, and the presence of diseases such as anemia and erythrocytosis can be determined by testing the number of red blood cells. In addition, there are 10% of senescent red blood cells, which are destroyed by mechanical shock in the blood vessels, and the released hemoglobin will bind to the haptoglobin in the plasma and then be taken up by the liver, and excessive destruction of red blood cells can cause hemolytic anemia. The protein inside red blood cells is mainly hemoglobin, and the main function of red blood cells is to transport oxygen and carbon dioxide. If the number of red blood cells in human peripheral blood and the concentration of hemoglobin are lower than normal, it is called anemia.