A Blood Group System is defined as one or more blood group traits (antigens) related to a single gene or two or more closely linked genes that contain the information to generate them. There are 30 identified blood groups and more than 600 known antigens besides A, B, and RH.

The ability to identify and match blood groups types is important for blood transfusions, but also in pregnancy and before certain types of transplantation. Some blood types are associated with inheritance of other diseases for example, the Kell antigene is sometimes associated with McLeod syndrome. Also certain blood types may affect susceptibility to infections, an example being the resistance to specific malaria species seen in individuals lacking the Duffy antigen.

Human blood is as valuable as oils and rare earth elements and considered an integral part of national strategic resources.