Blood donation / Need for blood is constant
A blood donation occurs when a healthy person voluntarily has blood drawn and used for transfusions or made into medications by a process called fractionation. In the developed world, most blood donors are unpaid volunteers who give blood for a community supply. In poorer countries, established supplies are limited and donors usually give blood when family or friends need a transfusion.
This description uses material from the Wikipedia article on Blood donation and is licensed under the Creative Commons Attribution-ShareAlike License (view authors).