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In an emergency situation where a patient’s blood type is unknown, type O negative blood is the only blood type that is safe to use. The reason is that it is compatible with all blood types. Type O negative is known as the universal blood type.
Type O negative blood has no antigens, it will not trigger an immune response, even if the recipient has a different blood type. As you might imagine, it’s a very popular resource on hospital shelves. That’s why O negative blood is in high demand yet in short supply.
Antigens are surface proteins found on red blood cells. Type O negative blood is the only blood type with no antigens.
Blood type A has an A antigen, while blood type B has a B antigen. Blood type AB has both A and B antigens. Blood type O has neither. But assigning a letter is just the first step in determining your specific blood type.
In addition to the aforementioned A and B antigens, blood is classified based by the presence of the Rh factor. Blood types with the Rh factor are considered Rh positive, and those without it are considered Rh negative. When we account for A and B antigens as well as the Rh factor, we get the eight most common blood types: A+, A-, B+, B-, O+, O-, AB+ and AB-.
Our immune system works to protect us from such invaders as bacteria and viruses. Our immune system recognizes the antigens present in our own blood type, but it may go into defense mode if it detects antigens from a different blood type. If mismatched blood is given during a transfusion, the body may fight back, potentially endangering the life of the patient.
About 43% of the population has type O blood, either positive or negative. O positive blood can’t be used universally because it has the Rh factor, but it is compatible with all positive blood types including O+, A+, B+, and AB+. Since over 80% of the population has a positive blood type, type O positive blood is in high demand. In some cases, it is used if the O negative blood is not available.
In contrast with O positive blood, O negative blood is relatively rare. Only about 1 in 15 people (approx. 7% of the population) have the universal blood type.
Universal donors play an important role in meeting this need and saving lives. Are you a universal donor? Make an appointment today and find out your blood type.