Blood is available to be shipped to hospitals 24 hours a day, 7 days a week. Hospitals typically keep some blood units on their shelves. Physicians determine whether the patient requires a transfusion and, if so, which type. Blood transfusions are given to patients in a wide range of circumstances, including serious injuries (such as in a car crash) surgeries, child birth, anemia, blood disorders, cancer treatments, and many others. See How Blood Donations Help.A patient suffering from an iron deficiency or anemia may receive red blood cells to increase their hemoglobin and iron levels, improving the amount of oxygen in the body. Patients who are unable to make enough platelets, due to illness or chemotherapy, may receive platelet transfusions to stay healthy. Plasma transfusions are used for patients with liver failure, severe infections, and serious burns.