Blood bank, site or mobile unit for collecting, processing, typing, and storing whole blood, blood plasma and other blood constituents. Most hospitals maintain their own blood reserves, and the American Red Cross provides a nationwide collection and distribution service. The Red Cross collects about 50% of the blood for the nation's blood banks. The Food and Drug Administration licenses blood banks.

Whole blood may be preserved for up to 21 days without losing its usefulness in blood transfusions; an anticoagulant is added to prevent clotting. Blood plasma, the fluid portion of the blood, may be frozen and/or dried and stored indefinitely. Blood and donors are screened for hepatitis, AIDS, malaria, and other infectious diseases. The potential risk of acquiring AIDS or hepatitis through transfusions has made it a common practice among patients anticipating surgery to “bank” their own blood before it is needed.