The A-B-O on Blood Types

As a phlebotomist, or a phlebotomy training student, blood is kind of your thing. Not in the vampire sense, of course. As in, an artist works in oil paints, a sculpture works in clay and you work with needles and blood all day! So how about a little refresher on all things blood types?

B is for Blood
All blood is created equal and is made of the same basic elements; however, not all blood is alike. In fact, there are...jump in when you know the answer...eight different common blood types. So what makes each one different from the next? A person’s blood type is determined by the presence or absence of certain antigens - substances that can trigger an immune response if they are foreign to the body.

Blood Groups and How They Get Along
There are four major blood groups determined by the presence or absence of two antigens – A and B – on the surface of red blood cells:

Group A – has only the A antigen on red cells (and B antibody in the plasma)
Group B – has only the B antigen on red cells (and A antibody in the plasma)
Group AB – has both A and B antigens on red cells (but neither A nor B antibody in the plasma)
Group O – has neither A nor B antigens on red cells (but both A and B antibody are in the plasma)

Got all that straight? Now things get a little trickier! In addition to the A and B antigens, there is a third antigen called the Rh factor, which can be either present (+) or absent ( – ).

How Is Blood Type Determined?
It’s inherited. Like eye color, blood type is passed genetically from your parents. Whether your blood group is type A, B, AB or O is based on the blood types of your mother and father.

Most Common Blood Type
Surely you know this one! If you said O positive, you are correct!