Blood Typing: Blood Mixing and Transfusions & Positive and Negative Blood

Have you ever wondered why people bother with blood typing? Or why people who donate blood have to have their type verified first?

Is because blood typing is very important when doctors make transfusions or mix different kinds of bloods. In fact, there is a whole field devoted to taking blood samples and studying them: its called Phlebotomy.

There are several different kinds of blood (A, B, AB, O, positive or negative, etc). They are usually based on two systems, the AbO system (A, B, AB, and O) and the Rh system (positive or negative). The Rh system classifies blood as positive or negative depending on whether or not it contains the RhD antigen. If it does, it is positive, and if it does not, it is negative and likely to make anti-RhD if exposed to the RhD antigen through transfusion. Therefore, when you receive a blood transfusion, the type of blood you receive should match your own blood type. If it doesn't, your immune system may form antibodies and begin attacking the donor blood because it does not recognize it. However, a person with blood type AB can receive from either A, B, or O individuals but can only donate to another person with AB type blood. Someone with blood type A can donate to either an A or AB, but can receive from O (because it does not have any antibodies) and other people with type A blood. Type B blood can be donated to either AB or B and can receive from either B or O. Type O blood can donate to any of the other types (A, B, AB) but can only receive from O.