Blood transfusion is the process of transferring blood or blood products into one's circulation intravenously. Transfusions are used for various medical conditions to replace lost components of the blood. Early transfusions used whole blood, but modern medical practice commonly uses only components of the blood, such as red blood cells, white blood cells, plasma, clotting factors, and platelets.
It is allowed to receive blood from any human being after being sure that is healthy blood. Blood is always Najis whether it is from Muslim or non Muslim. When blood transfusion is allowed , there is no question of any harm from it.