Whole blood includes blood cells and plasma such as red blood cells, white blood cells, and platelets, and component blood is one of the components, such as suspended red or white blood cells, and platelet suspension or simple plasma. There is a difference between component blood and whole blood when donating blood. When donating whole blood, the donor’s blood is taken directly from the donor. In the case of component blood, one of the donor’s blood components is taken and the other components are infused back into the donor’s body. Clinically, platelets are often used as component blood. For patients with low platelets, direct transfusion of platelets is more effective than transfusion of whole blood because the platelet concentration of component blood is high and its potency is high, and it can also minimize some of the allergic reactions associated with whole blood transfusion. There are also some coagulation factor deficiencies, plasma can be transfused to supplement the coagulation factors. Component blood is equivalent to supplementing what is lacking. In case of acute hemorrhage, which can lead to a decrease in whole blood cells, it is more appropriate to transfuse whole blood at this time. It is recommended to go to the hospital for further counseling, and blood transfusion should be performed under the supervision of a physician.