MODEL RELEASED. Blood transfusion patient talking on a mobile phone. The blood bags attached to the stand (upper left) are being used to add blood to her bloodstream. Elevating the blood bags above the patient allows gravity to be used to provide the pressure to add the blood. Blood transfusions are carried out to replace blood in people with blood disorders, or those who have lost blood through trauma or surgery. The blood group and type needs to be matched to that of the patient. Common blood disorders that can require regular transfusions include thalassaemia, anaemia and haemophilia.