Blood typing is a laboratory test done to determine a person's blood type based on the proteins on the surface of blood cells. If the person needs a blood transfusion, another test called crossmatching is done to find blood from a donor that the person's body will accept. People must receive blood of the same blood type, otherwise, a serious, even fatal, transfusion reaction can occur.

A child inherits genes from each parent that determine his blood type. This makes blood typing useful in paternity testing. Legal investigations may require typing of blood to identify persons involved in crimes or other legal matters.

Blood typing and crossmatching tests are performed in a blood bank laboratory by technologists trained in blood bank and transfusion services. The tests are done on blood after it has been separated into cells and serum. Serum is the...