350ml /450 ml of blood is collected from a donor into a plastic bag containing an anticoagulant. This is called 1 unit of whole blood. Whole blood can be used as it is, or is separated into blood components Types of blood components:- Red blood cell concentrate (packed red blood cells) Platelet concentrate. Fresh frozen plasma. Cryoprecipitate. The separation of blood into components means that patients can be treated with the specific fraction of blood that they lack. This reduces the chances of adverse reactions to unnecessary administration of blood constituents and ensures that more than one patient can be treated using blood from one donor.