Whole blood (WB) is human blood from a standard blood donation. It is used in the treatment of massive bleeding, in exchange transfusion, and when people donate blood to themselves. One unit of whole blood (~517 mls) brings up hemoglobin levels by about 10 g/L. Cross matching is typically done before the blood is given. It is given by injection into a vein.

Side effects include red blood cell breakdown, high blood potassium, infection, volume overload, lung injury, and allergic reactions such as anaphylaxis. Whole blood is made up of red blood cells, white blood cells, platelets, and blood plasma. It is best within a day of collection; however, can be used for up to three weeks. The blood is typically combined with an anticoagulant and preservative during the collection process.

The first transfusion of whole blood was in 1818; however, common use did not begin until the First and Second World Wars. It is on the World Health Organization's List of Essential Medicines. In the 1980s the cost of whole blood was about US$50 per unit in the United States. Whole blood is not commonly used outside of the developing world and military. It is used to make a number of blood products including packed red blood cells, platelet concentrate, cryoprecipitate, and fresh frozen plasma.