Blood type Blood type or blood group is a medical term. It describes the type of blood a person has. This blood type is based on whether or not there are substances on the outside of red blood cells that can cause an allergic reaction when it comes into contact with certain other blood cells. These substances are called antigenic substances or also antigens.

When a blood transfusion or an organ donation takes place, it is important to know what type of blood the donor (who gives blood) and the receiver (who needs blood) have, so that the receiver's blood does not have an allergic reaction to the donor's blood. This can be very dangerous for the receiver.

People with type O negative blood are often called universal donors because they can give blood to any other bloodgroup. People with type AB positive blood are called universal recipients because they can receive blood from any other bloodgroup. Of course, before a transfusion takes place, the blood is also tested thoroughly for all sorts of other things that might cause problems for the receiver.

In a laboratory, blood is tested for antigens. When a certain antigen is found, there are also always particular antibodies found. These antibodies will attack any antigens that it does not recognise. Group A (with the A-antigen) has Anti-B antibodies Group B (with the B-antigen) has Anti-A antibodies Group AB (with both A and B-antigens) has no antibodies Group O (with no antigens) has anti-A and anti-B antibodies

Rh blood group system The commonly used terms Rh factor, Rh positiveand Rh negative refer to the D antigen only. Besides its role in blood transfusion, the Rh blood group system specifically, the D antigenis used to determine the risk of hemolytic disease of the newborn as prevention is key.

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