Fewer Than 50 People in the World Have This Incredibly Rare Blood Type

This blood type is so rare that scientists call it “golden”—but the pretty name masks the fact that this type can be dangerous for people living with it.

blood type - determination; Blood group and rh factor testing by agglutination methodPhoto: Anarette/Shutterstock

Is this the rarest blood type in the world?

Maybe you know your blood type off the top of your head—or maybe you’re like most Canadians and you have no clue. You should probably find out. Here’s one reason: You could have “golden blood.” And while having golden blood might sound exciting, this incredibly rare type has the potential to be deadly for people who have it. (Here are seven ways to maintain healthy blood sugar levels.)

Each of the common blood types—A, B, AB, and O—comes in negative and positive versions. Of these eight main categories, O positive is the most common, according to Canadian Blood Services. AB negative is identified as the least common blood type in Canada; less than one per cent of the population has it.

While that sounds pretty rare, AB negative has nothing on the rarest blood type of all—one that fewer than 50 people in the entire world have—which is why scientists have nicknamed it “golden blood.” The type, whose scientific name is Rhnull blood, was discovered in 1961. Since then, there have been a total of 43 reported cases. Its rarity and unique properties combine to make it potentially dangerous, should someone with this type ever need a blood transfusion. (These are the diseases doctors are most likely to miss.)

The reason identifying your blood type is so important is that your red blood cells have receptors called antigens. If you receive a transfusion, your immune system will only accept the antigens that match your blood type. If you get the wrong type—and a mismatched set of antigens—+your immune system will attack the blood cells, with disastrous and potentially deadly results for you. The rarest blood type, Rhnull blood, is so called because it’s completely missing the most common type of antigen, Rh. This means that if you have it, receiving a transfusion of a blood type with any Rh antigens will cause your body to reject the blood. (Read about eight unsolved medical mysteries that still stump doctors.)

Since 99.9999994 per cent of people have blood with Rh antigens, finding a blood donor for Rhnull individuals can be nearly impossible. This is why people who have golden blood are encouraged to donate their blood in case they ever need blood, and because others with rare blood types could benefit from it. Since Rhnull blood contains no Rh antigens to be rejected, it can be “a universal donor for those with generally rare blood types,” according to David Barbour, co-founder of Vivio Life Sciences.

Golden blood, therefore, can be both life-threatening and lifesaving. And while your chances of having the rarest blood type are incredibly low, finding out your blood type is the only way to know for sure.

This man’s blood donation has saved the lives of 2.4-million—and counting!

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Originally Published on Reader's Digest