Every two seconds, someone in the U.S needs a transfusion of red blood cells. Every 15 seconds someone in the U.S. needs a platelet transfusion. But not just any blood will do. For a successful outcome, the donor and the patient must have compatible blood types.
Recent studies show that there is a need for blood transfusions every 2 seconds. The average person can only donate 1 pint of whole blood in a single donation and the shelf life is 42 days, which is why the need to keep replenishing the supply to meet demands is great.