In the United States, 45% of the blood donated by blood donors is type O blood. Type O blood is essential in emergency situations because there is no time to test the blood type of the recipient in emergency situations, and type O blood can be used by anyone. Type O blood is unique in that it is compatible with all types of blood, so people of any blood type can accept it, but because of this characteristic, type O blood is chronically in short supply. From this we know:. ['Blood donors of type O are becoming more popular.', "The special purpose of B. O blood is that it is the same as most people's blood types.", "Transfusion of non-O blood to the recipient must know the recipient's blood type.", 'In the U. S. , 45% of people have blood type O, and type O is the blood type common to most people.']