Blood Types Provide Important Clues About Our Health
They key to your health is running through your veins. ABO blood types can tell us which diseases we’re most at risk for.
Blood types are important when it comes to donating blood or having a transfusion. They’re also a good indicator of your potential health risks. Those with certain blood types are genetically predisposed to various illnesses, for instance. From heart disease to cancer, your specific blood type could alert you to an underlying risk.
How Many Blood Types are There?
According to the American Red Cross, “there are eight common blood types and many rare ones.” The main human blood group is ABO, which is genetic and determined by genes A and B.
Each of the blood types is determined by the presence or absence of certain antigens (i.e. a toxin or foreign substance that can trigger an immune response) on the surface of red blood cells. To make things even more confusing, there is also a protein, known as the Rh factor, which can be present or absent on the cells. If it’s on the cells, you’ll add a + after your blood type. If it’s absent, you’ll add a –.
Confused? This blood types chart should help:
| Group A | Group B | Group AB | Group O | Rh factor |
| Has the A antigen on its red blood cells | Has the B antigen on its red blood cells | Has both A and B antigens on its red cells | Has neither A nor B antigens on its red blood cells | If this protein is present on the red blood cells, a person will be a member of the A+, B+, AB+, or O+ blood group |
| Has the B antibody in its plasma | Has the A antibody in its plasma | Has neither A nor B antibodies in its plasma | Has both A and B antibodies in its plasma | If this protein is absent on the red blood cells, a person will be a member of the A-, B-, AB-, or O- blood group |
| A person is A+ if the protein Rh factor is present | A person is B+ if the protein Rh factor is present | A person is AB+ if the protein Rh factor is present | A person is O+ if the protein Rh factor is present | |
| A person is A- if the protein Rh factor is absent | A person is B- if the protein Rh factor is absent | A person is AB- if the protein Rh factor is absent | A person is O- if the protein Rh factor is absent |
Now that you (kind of) understand the ABO blood types, there are over 600 more known antigens which can create what the American Red Cross calls, “rare blood types.” Some blood types are unique to a specific racial or ethnic group, which can make it difficult to find suitable blood donors.
Can A Type O Donate Blood to Everyone?
Just because you’re healthy doesn’t mean you can give your blood to just anyone. Certain blood types don’t mix. Types As can’t share with Type Bs, for instance and vice versa. And no one can share with an O unless he, too, is a member of that blood group. That said, type O is the most universal, meaning it can be shared with all blood types.
“Type O is considered a ‘universal donor’ because the type O blood group antigen does not engender a transfusion reaction by the antibodies possessed by the other blood groups,” explains Dr. Peter D’Adamo, Distinguished Professor of Clinical Medicine at the University of Bridgeport and Director of the Center of Excellence in Generative Medicine. “The true universal donor type is O-, as this then also rules out antibody reactions by the Rhesus (Rh) system.” However, if you’re in need of plasma (the liquid necessary to transport red and white blood cells and platelets throughout the body), type AB blood is considered the universal plasma donor.
Which Is the Most Common Blood Type?
Type O positive is the most common of all blood types. The percentage of those with this (and all other blood types), however, varies depending on ethnicity. According to the American Red Cross, about 45 percent of Caucasians have type O, for instance, while nearly 51 percent of African-Americans and almost 40 percent of Hispanics share this common blood type. The rarest blood type is AB, which is only shared by about 4 percent of the overall population.
What Do Blood Types Say About Your Health?
Blood types can determine your risk of certain illnesses such as cancer and cardiovascular disease. Blood types can also help pinpoint your likelihood of suffering from inflammation and neurodegenerative ailments, says Dr. D’Adamo. “In general, the studies (some going back to the 1940s) have shown an increase in cancer and cardiovascular disease in people with blood types A and AB, inflammation and depression in type O, and neurodegenerative ailments in blood types B and AB.” Most often, your risk of getting these conditions, though, will depend also on external factors such as diet, fitness, and lifestyle.
Blood Types and Their Associated Disease Risks
| Type A | Type B | Type AB | Type O |
| Increased risk of cardiovascular disease and cancer | Increased risk of neurodegenerative ailments | Increased risk of cardiovascular disease and cancer | Increased risk of depression and inflammation |
| Increased risk of neurodegenerative ailments | Increased risk of peptic ulcers |
Blood Types in the U.S. Population
The following chart represents the percentage of those with a certain blood type in the US, according to the American Red Cross.
| Type A+ | Type A- | Type B+ | Type B- | Type AB+ | Type AB- | Type O+ | Type O- |
| Caucasian – 33% | Caucasian – 7% | Caucasian – 9% | Caucasian – 2% | Caucasian – 3% | Caucasian – 1% | Caucasian – 37% | Caucasian – 8% |
| African-American – 24% | African-American – 2% | African-American – 18% | African-American – 1% | African-American – 4% | African-American – 0.3% | African-American – 47% | African-American – 4% |
| Asian – 29% | Asian – 2% | Asian – 9% | Asian – 1% | Asian – 2% | Asian – 0.2% | Asian – 53% | Asian – 4% |
| Latino-American – 27% | Latino-American – 0.5% | Latino-American – 25% | Latino-American – 0.4% | Latino-American – 7% | Latino-American – 0.1% | Latino-American – 39% | Latino-American – 1% |
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This article was originally published in 2018. It is regularly updated.
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Only 7 percent of Americans have O- blood, which can be transfused to people of all blood types. It’s always in high demand and short supply.
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