A blood transfusion is the transplantation of a foreign liquid organ. Blood components and plasma derivatives are prescription medications and may only be dispensed upon a doctor's order. The physician treating the patient is required to have fundamental clinical transfusion medicine knowledge for the differentiated handling of blood components and plasma derivatives. This work provides assistance and conveys basic knowledge about blood products and transfusions for non-transfusion specialists. It describes, among other things, the risks of blood transfusions, the fundamentals of blood group serology, the composition of blood and blood products, and the management of transfusion incidents; it also addresses the current transfusion law and the guidelines for blood transfusion, as well as the regulation and administration of blood.