Why are blood transfusions used?

You may need a blood transfusion if you have: A severe infection or liver disease that stops your body from properly making blood or some parts of blood. An illness that causes anemia, such as kidney disease or cancer. Medicines or radiation used to treat a medical condition also can cause anemia

Blood transfusions are used when a patient has lost a lot of blood or that they cannot make anymore blood and need a transfusion of blood from a donor that has the same type of blood as them.