Show Medically reviewed by Alana Biggers, M.D., MPH — Written by Danielle Dresden on June 14, 2020
Blood types are a classification of blood based on the antigens present on red blood cells. Antigens are molecules that can trigger an immune system response. There are eight common blood groups but 36 human blood groups in total. A blood transfusion is a procedure that restores blood to the body. It is essential that people undergoing the procedure receive the correct blood type, or it will trigger the immune system, causing sickness and complications. According to the American Red Cross, roughly every 2 seconds, a person in the United States requires a blood transfusion. They also note that this procedure saves 4.5 million lives each year. In this article, we discuss the rarest and most common blood types by ethnicity. People can define blood types using the ABO and Rhesus (Rh) blood group systems. These define blood types according to which antigens are present on red blood cells. ABO systemThis system classifies blood types as follows:
Rh systemRed blood cells may have another antigen called the Rh antigen on their surface. If it is present, the blood group is Rh-positive, but if it is absent, the blood group is Rh-negative. Combining these two characteristics yields the eight most common blood types. Most people have one of these types:
The genes that a person inherits from their parents determine the mix of antigens and proteins in their blood. Due to this genetic factor, the American Red Cross suggest that when people need blood, especially those with rare blood types, the best matches tend to come from people of the same race or ethnic background. Inherited characteristics, such as blood types, tend to run in ethnic groups. To increase the likelihood of well-matched blood types, experts recommend matching donors and recipients along ethnic lines, particularly for rare blood types. For this reason, some blood centers collect ethnic information from blood donors. For some conditions, such as thalassemia and sickle cell disease, this matching is even more important because these conditions are more common among certain ethnic communities, and people may need frequent transfusions. For example, only 2% of donors have a rare subtype of blood that doctors often use to treat sickle cell disease, but demand for it is increasing by 10–15% each year. The rarity of and demand for this type of blood emphasize the importance of blood donors. Click here to learn more about blood types. In the U.S., 38% of the population have O-positive blood, making it the most common blood type. According to the American Red Cross, the following statistics show the most common blood types in the U.S.:
The least common blood type in the U.S. is AB-, with less than 1% of the population having this type. Statistics from the American Red Cross show that the following are the most rare forms of the major eight blood types in the U.S.:
A and B antigens only represent two of approximately 600 other known antigens that can differentiate blood types. It is important to make a distinction between the rarest of the eight most common blood types and the extremely rare subtypes. Having an antigen that most people do not have, or missing an antigen that most people do have, means that an individual has a rare blood type. According to the International Society of Blood Transfusion, if only 1 in 500 people are missing the same antigen as an individual, their blood type is rare. If only 1 in 1,000 people lack it, the individual’s blood type is very rare. In addition, scientists have identified 36 different blood group systems, some of which can cause problems with blood transfusions. Some of these rare blood types and blood group systems are distinctly more common in certain ethnic groups. The American Red Cross data below list the rare blood type and the ethnic group in which it is most common:
Some of these blood types are extremely rare. For instance, researchers estimate that just 1 in 6 million people have the RzRz blood type. Blood types are based on the different antigens and proteins present on red blood cells. To make sure that a transfusion supports an individual’s health instead of causing harm, there must be a good match between the donor’s blood type and that of the recipient. As an individual’s genetic background influences their blood type, looking at the most common blood type by race or ethnicity can help healthcare professionals acquire and effectively use the most suitable blood and blood products for individuals requiring blood transfusions. Last medically reviewed on June 14, 2020
In general, the rarest blood type is AB negative and the most common is O positive. Here's a breakdown of the most rare and common blood types by ethnicity, according to the American Red Cross. O positive:
O negative:
A positive:
A negative:
B positive:
B negative:
AB positive:
AB negative:
How is blood type determined?A person's blood type is based on whether or not they have certain molecules or proteins — called antigens — on the surface of their red blood cells, according to the National Institutes of Health. Two of the main antigens used for blood typing are known as "A antigen" and "B antigen." People with type A blood only have A antigens on their red blood cells and those with type B blood have only B antigens. Individuals with type AB blood have both; people with type O blood have neither. Another protein, the "Rh factor" — also known as the "Rhesus" system — is also present or absent on red blood cells. A person's blood type is designated as "positive" if they have the Rh protein on their red blood cells, and "negative" if they don't have this protein. Is blood type genetic?Yes, a person's blood type is genetic, inherited from his or her parents, according to the Red Cross. Blood type and transfusionsBlood typing is particularly important for blood transfusions, because certain antigens on blood cells can trigger a person's immune system to attack the donated blood. People who are Rh-negative can only receive Rh-negative blood, but people who are Rh- positive can receive either Rh-positive or Rh-negative blood, the Red Cross says. What's more, type A blood can be used for transfusions for patients with type A or type AB blood; type B blood can be used for patients with type B or type AB blood; and type AB blood can be used for patients with type AB blood. Type O blood can be used for patients with type A, type B, type AB and type O blood. What blood type is the "universal donor"?People with type O blood are called "universal donors" because this type can be used for patients with any blood type. Type O blood is often in short supply in hospitals, due to demand for this universal donor type, according to the Red Cross. In particular, type O-negative blood is in high demand because it's the one most often used for emergencies, when there may not be time to determine a patient's blood type. What are "rare" blood types?Although ABO and Rh groups are the most important blood groups for transfusions, there are hundreds of other antigens that have been found on the surface of people's red blood cells. A person's blood type is rare if their blood does not have an antigen that most people have, or if their blood does have an antigen that most people lack, according to the Cleveland Clinic. Specifically, rare blood types are those that are found in 1 in 1,000 people or fewer. One of the rarest blood types in the world is known as "Rh-null;" fewer than 50 people in the world have been found to have this blood type, earning it the name "golden blood," the Cleveland Clinic says. Can blood types change?A person's blood type does not usually change, meaning it stays the same throughout life. But in some rare cases, blood type has been known to change, including in cases of bone marrow transplants and in people who developed certain types of cancers or infections, according to the Cleveland Clinic. Blood type and pregnancyBlood type can be an issue in pregnancy if the mother is Rh negative and the fetus is Rh positive. (The fetus can inherit the Rh factor from either the mother or the father.) That's because, in this situation, the mother's immune system can react to the fetus' "positive" blood. For this reason, pregnant women have their blood tested to determine blood type. Those with Rh-negative blood can be treated with a drug called Rh immunoglobulin to prevent a damaging immune reaction if their fetus has a positive blood type, according to the Cleveland Clinic. How to find out your blood typeIf you don't know your blood type you can ask your health care provider if they have a record of it. If they don't, you may be able to request blood typing the next time you get your blood drawn, according to CNN. You can also find out your blood type if you donate blood, according to the Cleveland Clinic. There are also at-home blood tests that can tell you your blood type. Additional resourcesThis article is for informational purposes only, and is not meant to offer medical advice. This article was updated on Sept. 10, 2021 by Rachael Rettner. |