A- blood? Sounds pretty good. But don’t confuse it with your high school biology scores. Blood types aren’t “graded,” and one isn’t necessarily better than another. In other words, your A- blood isn’t superior to your friend’s B+ blood. (Sorry.)
That said, some blood types *are* more rare, which makes them a bit more needed (and thus valuable) at blood donation banks. And then there’s that highly prized label of “universal donor,” which means that your blood type can be given to anyone.
What Blood Types Actually Mean
Blood types are mostly relevant when it comes to blood transfusions (when someone loses a lot of blood and needs another person’s donated blood). Because the immune system tends to react and attack foreign cells, it’s important to transfuse blood that matches the blood of the patient in need.
Researchers categorize blood types based on the presence of antigens in red blood cells, according to the American Red Cross. These antigens are what can set off the immune system.
The two main antigens are known as A and B antigens, and they can exist on the surface of the red blood cells or within the plasma. A person’s blood may contain one type of antigen, both types of antigens, or neither antigens. The A blood types contain only the A antigen, the B blood types contain only the B antigen, and the AB blood types contain both A and B antigens.
As for the O blood types? They contain neither antigen, which makes them safe for anyone to receive in an emergency. That’s why O types are known as “universal donors,” and they’re very valuable at blood donation banks.
Additionally, some blood contains a protein called the Rh factor. Blood types contain a (+) or (-) label if the protein is present or absent, respectively.
The 8 Most Common Blood Types
All these variations lead to the most common blood types in the United States: A+, A-, B+, B-, O+, O-, AB+, and AB-. Here’s how many Americans have each type:
These blood types get the most attention, but there are other blood types out there that are even more rare. Donations from these blood types could prove beneficial for treating conditions like sickle cell anemia.
About 5 million patients receive blood transfusions each year, according to the Centers for Disease Control and Prevention. That’s one person every two seconds. If you are able, consider donating your blood—no matter what type. Learn more about preparing to donate blood safely here.