Patients requiring blood almost never receive transfusions of whole blood. Instead, a patient typically receives only the components necessary to treat their clinical condition. Therefore, whole blood donations must be processed to separate out each component. Each component plays a different role in the health and survival of a patient.

		Red blood cells comprise 40-50% of blood volume. They carry oxygen to vital organs and are required by surgical patients who lose blood during surgery or by trauma victims who have lost blood as a result of an accident or injury. Red blood cells that have been donated can be stored in a refrigerator for up to 42 days. If they are not used within six weeks, they must be thrown away. Red blood cells can also be stored frozen for up to 10 years. Red cells are the most commonly transfused blood component and most whole blood collections are done with the specific intent of capturing the red cell component.
Red Blood Cells carry oxygen to organs.
		Platelets account for a small percentage of whole blood volume. They are used therapeutically to control bleeding and are often transfused in multiple doses to cancer patients undergoing chemotherapy. Platelets must be stored at room temperature to retain their viability. Therefore, they have only a five-day shelf life before they must be discarded due to possible growth of bacteria.
Platelets aid in clotting.
		Plasma: The remainder of blood volume is plasma, a watery substance in which proteins that trigger blood-clotting mechanisms are suspended. Plasma can be transfused directly to a patient, but, more often, plasma is used as a raw material for pharmaceuticals. Plasma is “fractionated” into its different protein components, which are then manufactured into pharmaceuticals. Factor VIII, which is required by hemophiliacs to control bleeding, is one such plasma-derived medicine. Plasma can be stored frozen for up to one year.
Plasma: the fluid portion of blood.