What's Your Type?



In some ways, every person's blood is the same. But, when analyzed under a microscope, distinct
differences are visible. In the early 20th century, an Austrian scientist named Karl Landsteiner
classified blood according to those differences. He was awarded the Nobel Prize for his
achievements.

Landsteiner observed two distinct chemical molecules present on the surface of the red blood cells.
He labeled one molecule "A" and the other molecule "B." If the red blood cell had only "A" molecules
on it, that blood was called type A. If the red blood cell had only "B" molecules on it, that blood was
called type B. If the red blood cell had a mixture of both molecules, that blood was called type AB.
If the red blood cell had neither molecule, that blood was called type O.

If two different blood types are mixed together, the blood cells may begin to clump together in the
blood vessels, causing a potentially fatal situation. Therefore, it is important that blood types be
matched before blood transfusions take place. In an emergency, type O blood can be given because
it most likely to be accepted by all blood types. However, there is still a risk involved.

A person with type A blood can donate blood to a person with type A or type AB. A person with
type B blood can donate blood to a person with type B or type AB. A person with type AB blood
can donate blood to a person with type AB only. A person with type O blood can donate to anyone.

A person with type A blood can receive blood from a person with type A or type O. A person with
type B blood can receive blood from a person with type B or type O. A person with type AB blood
can receive blood from anyone. A person with type O blood can receive blood from a person with
type O only.

Because of these patterns, a person with type O blood is said to be a universal donor. A person with
type AB blood is said to be a universal receiver. In general, however, it is still best to mix blood of
matching types and Rh factors.