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.

 The Red Cross and a number of other organizations run programs, known as blood banks, to collect, store, and distribute blood and blood products for transfusions. When blood is donated, its blood type is determined so that only appropriately matched blood is given to patients needing a transfusion. Before using the blood, the blood bank also tests it for the presence of disease-causing organisms, such as hepatitis viruses and human immunodeficiency virus (HIV), the cause of acquired immunodeficiency syndrome (AIDS). This blood screening dramatically reduces, but does not fully eliminate, the risk to the recipient of acquiring a disease through a blood transfusion. Blood donation, which is extremely safe, generally involves giving about 400 to 500 ml (about 1 pt) of blood, which is only about 7 percent of a person’s total blood.

 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.

 Many blood banks also have facilities for apheresis , bone marrow donations, and related procedures. Some centers save umbilical cord blood (blood that is especially rich in stem cells ) for use in treatments; however, the cost of preparing and storing such blood is much higher than that of normal blood. Sometimes parents store their newborn's cord blood at a private cord blood bank in case the child has need of it, but the use of one own's cord blood is ineffective or undesirable in many diseases where such blood is used as a treatment.