In general, 2 units of suspended red blood cells are around 220 ml, because one unit of suspended red blood cells is extracted from 200 ml of whole blood, and then other anticoagulants are added, usually the volume of 1 unit of suspended red blood cells is 110 ml, so the volume of 2 units of suspended red blood cells is 220 ml. In clinical practice, according to the degree of anemia and the patient’s weight, we can roughly calculate the possible increase of the patient’s hemoglobin after transfusion of 2 units of suspended red blood cells. Therefore, the general hemoglobin can be increased by 8-10g/L with the infusion of 2 units of suspended red blood cells.