Because you could prolong someone's life.
Blood comes only from people - no other source is currently available.
Volunteer donors are needed on a daily basis to give blood for the thousands of patients who use it. If you have never donated before, you may be surprised to find how easy, quick and relatively painless it is. It is impossible to get AIDS or any viral disease by donating blood. Your single donation can be used to help several patients at once because blood is separated into red blood cells, platelets and plasma. These components are given to patients suffering from leukemia or hemophilia, to accident victims, to patients undergoing chemotherapy or to patients who have lost blood during surgery.