ONE MEDAL!! In blood drives there are certain blood types which are more sought after than others. What blood type can be used in more transfusions than the others? Which can be used least often?

Question

anonymous · Answer

O-type blood is used more often because it has no proteins on the blood cells so everyone can receive them.
A-type blood means it has A proteins, and since you cannot introduce new proteins to blood that doesn't have it originally, A can only donate to other A's or to AB's. B-type blood can only donate to B's and AB's. 
However because AB-type blood has both A and B proteins, they can only donate to AB's. Because of this, they are used least often in blood transfusions.