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Your Photo Guide to Understanding Blood Types

Determining Your Blood Type

Blood types are classified based on the presence of certain substances on the surface of red blood cells. These are known as antigens and include proteins, carbohydrates, glycoproteins, and glycolipids. Like hair or eye color, your blood type is inherited genetically. The four primary types are A, B, AB, and O. 

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O Blood Type

Type O blood is the most common type in the United States, with 38% of the population falling into this category. Because type O blood has neither A or B antigens on its red blood cells, it can be donated to people of any type. Despite this, type O's can only receive blood from other type O's. 

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A Blood Type

Type A is the second most common blood type in the United States, with 34% of the population having it. If you fall into this group, you can donate blood to other type A's, as well as those with Type B. However, you can only receive from those with Type A or Type O. 

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B Blood Type

Type B is a relatively rare type for those living in the United States. If you are type B, you can donate blood to others with type B or those who are AB. Type B is considered the opposite of A—meaning that the antigens found in this type are absent in A blood and vice versa. 

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AB Blood Type

Only about 4% of Americans have an AB blood type. However, those who do have red blood cell antibodies found in both type A and B blood. While no other blood type can accept AB blood, those with it are universal recipients—meaning they can receive from all other types. 

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Testing Blood Type

The test to determine your blood type is called ABO typing. This procedure uses the process of elimination to determine it by mixing a sample of your blood with different antibodies to see if the blood agglutinates (sticks together). If the blood cells do stick together, this means that the blood reacted with one of these antibodies. 

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Importance of Blood Type

Receiving the wrong type of blood during a transfusion could have deadly consequences, which is why knowing your type is so important. If this occurs, your body's own blood cells will begin to attack the newly introduced blood in a process known as an ABO incompatibility reaction. Symptoms of this include fevers, chills, nausea, breathing problems, and a feeling of dread. 

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Blood Type Uses

Blood typing is used before blood transfusions and before a person donates blood to make sure blood donated and received is always compatible. Also, it is common for a pregnant woman to have a different blood type than her child. Blood typing is used to check the blood type of the unborn infant so that the mother is able to take a drug called RhoGAM, which will keep her body from attacking her baby’s blood cells if their blood becomes mixed. Blood typing is also used in forensics for crime scenes to confirm the identity of victims and assailants. 

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Blood Types in Eastern Cultures

There is a common belief in Japan and some other East Asian cultures that a person’s blood type is predictive of their personality, temperament, and compatibility with others. This belief is similar to the idea that astrological signs play an important role in a person's life and disposition. This idea is so pervasive that some companies produce blood type-specific products. 

 

Photo by Chris Gladis, 2009, CC BY-ND 2.0
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Changing Blood Type

Your blood type can change, technically. However, your genes do not change, and this only occurs in special circumstances. For example, some people have noticed that after receiving a bone marrow transplant, they sometimes will slowly develop their donor’s blood type. Additionally, scientists have discovered an enzyme that strips away blood cell antibodies, turning recipients into type O's. 

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