Blood group types (ABO blood group system)

Different blood group types on syringes

Humans inherit different traits and genes from their parents. Blood group is one of the things a person inherits from parents, and it cannot be changed after birth.

While everyone's blood is typically composed of the same basic parts, there are different blood types. It is important that you know your blood group type in order to determine the group you can donate blood to and the group you can receive blood from.

Since an individual's blood type depends on the genes inherited from parents, it causes a variation in blood composition between individuals.

Blood types are differentiated by differences in structure and antigen present on the surface of the red blood cells.

Even though there are up to 43 blood group systems recognized by the International Society of Blood Transfusion (ISBT), the two most important ones are the ABO blood group system and the Rh blood group system. This article will dwell on the former.

This article will discuss the ABO blood types, the blood group matching table, blood group testing (blood typing), and how it is performed.

First, it will start with discussing the blood types? What is a blood type?

Meaning of a blood group type

A blood type is also known as a blood group. It is the grouping of blood based on the absence or presence of blood plasma antibodies and inherited antigens on the surface of red blood cells.

The main components that make up the blood are:

  • Red blood cells, which are the carriers of oxygen
  • White blood cells which play a key role in the body's immune system
  • Blood platelets which aid in blood clotting
  • Blood plasma which is the yellowish fluid that contains proteins and salts.

Photo by ANIRUDH on Unsplash

According to the International Society of Blood Transfusion, the presence or absence of a specific antigen on the red blood cell surface is what determines a person's blood group type.

The antigens may be carbohydrates, proteins, glycolipids, or glycoproteins. In the case of the ABO blood group, the antigens present on the red cell surface are either glycolipids or glycoproteins.

But what are the ABO Blood group types?

The glycolipid and glycoprotein antigens on the red blood cell membrane divide the ABO blood group system into blood types, as seen below.

The 4 ABO blood types

The ABO blood group system is divided into 4 blood types, namely:

  • Blood type A
  • Blood type B
  • Blood type AB
  • Blood type O

Each blood type is characterized by the presence or absence of specific antigens and antibodies.

Both antigens and antibodies are involved in the body's immune system defense mechanism. White blood cells contain antibodies that fight off foreign antigens entering the body.

This means if an antigen that is incompatible with your body system enters your body, your antibodies will launch an attack on the antigen. This is the basis for blood type compatibility as antibodies from people with a particular blood group type recognize antigens from another blood group type as foreign and quickly attack them.

The discovery of the ABO blood group system was credited to Karl Landsteiner, who discovered the blood system in 1900. He ran broad research on serology which led to the discovery of the A, B, and O group types.

Other researchers followed up with his discovery, and soon blood transfusion and blood type testing came to light.

Below is a blood matching table to help you better understand blood group types and the antigens or antibodies present in each type.

Blood group matching table

People with blood group AB are known as universal recipients because they can receive blood from all the other blood groups, while people with blood group O are called universal donors because they can donate blood to all blood groups.

If you have blood group O, you may want to consider donating blood to blood bank centers. Consider this a service to humanity, as you could be saving many lives when you donate your blood.

If you are not sure where you can donate blood, you can speak to your doctor or visit a healthcare center close to you. They will direct you on where and how to donate blood.

How to know your blood type: Blood typing

You might be wondering how you can tell your blood group type. You simply have to run a blood test in a laboratory to determine your blood type.

Your red blood cells will be mixed with different antibody solutions during the blood typing test. The reaction of this mixture will tell your blood type.

For instance, if a solution carries anti-A antibodies and you have A antigens in your blood, the mixture will clump together, showing that your blood group is A.

Suppose your blood doesn't react to any of the anti-A or anti-B antibodies. In that case, yours should be blood group O. Series of tests will be carried out on your blood sample using different antibodies to identify your blood group.

It is advisable for intending couples to take blood typing tests to know their blood types. They can also look up their blood types in the blood group chart for marriage to know if their blood groups are compatible.

Relationship between blood groups and disease risks

Photo by CDC on Unsplash

Different studies have indicated a link between blood types and increased risk of developing certain diseases. This means your blood group type may affect your health.

Below are some diseases linked with each blood type.

Diseases linked to blood group O

A recent 2021 study indicated that people with blood type O had an increased incidence of tuberculosis infection, plague, cholera, and mumps.

Individuals with blood group O are more likely to develop these infections than other blood groups. However, people with blood group O are less susceptible to arterial and venous thromboembolism compared to people of other blood groups, according to a 2006 study.

Some works of literature have the view that blood group O came from Africa way before humans started migrating to different parts of the world.

Different studies suggest that this may be why blood group O, which is prevalent in different parts of the world, provides a selective advantage over severe malaria. The studies indicate that people with blood group O does not often suffer severe malaria.

Diseases linked to blood group A

People with blood group A may have an increased risk of Pseudomonas aeruginosa infection and smallpox.Pseudomonas aeruginosa is bacteria that infects and colonizes critical organs in the body such as the urinary tracts, lungs and kidneys.

Helicobacter pylori infections have been linked to blood group A and other non-O blood groups. Helicobacter pylori is the bacteria that causes stomach ulcers. This explains why stomach cancer is prevalent in blood group A.

Blood group A also has the highest risk of cardiovascular disorders such as coronary heart disease, stroke, and arterial and venous thromboembolism.

Diseases linked to blood group B

People with blood group B may have a higher risk of contracting salmonella and E.coli infections, tuberculosis, and gonorrhea.

Other diseases that have a higher incidence in blood group B include:

  • Hodgkin's lymphoma
  • Pancreatic cancer
  • Hypertension
  • Type 2 diabetes

Diseases linked to blood group AB

Blood group AB had an increased risk of E.coli and salmonella infections and smallpox, just like blood group B. Second to blood group A, people who have blood group AB have a high risk of developing cardiovascular disease, a 2016 study shows.

Furthermore, the study indicated that people with blood group AB might have the highest risk of developing type 2 diabetes. They also have more risk of having hypertension than blood type O but lesser risk than blood type A and B.

Other health conditions linked to blood group AB include pancreatic cancer, dementia, and cognitive impairment.

Why knowing your blood type is important

The Austrian scientist Karl Landsteiner discovered blood groups in 1900. Before then, doctors had no idea that people have different blood types. This ignorance led to many deaths via transfusion.

But now, health professionals know that when blood from two different or incompatible blood groups mixes, the blood can clump up. The result can be fatal as the recipient's antibodies attack the donor's blood cells (because the antigens don't match).

Thus, for a blood transfusion to be effective and safe, it is essential that the donor's and the recipient's blood groups match.

A donor doesn't always need to have the same blood type as the recipient (e.g., both donors must not have A blood type). Their blood types only have to be compatible (e.g., a person with AB blood type can receive blood from a person with A blood type).

For instance, a person with an O blood group can still donate blood to a person with blood group A.

Aside from helping hasten the transfusion process in emergency cases, knowing your blood type can also provide some useful insights into your health. As discussed above, studies indicated that some people have higher risks of developing certain health conditions based on their blood type.


The ABO blood system is divided into 4 blood types - A, B, AB, and O. These blood types are categorized depending on the presence of antigens on the red blood cell surface. One can only donate or receive blood from a compatible blood type. Also, each blood type is inherited from genes and cannot be changed after birth.

It is important that you know your blood type as that knowledge may come in handy in emergencies, such as when your spouse needs an immediate blood transfusion. Some diseases have also been linked to some blood group types.

You can visit a hospital close to you and request a blood test (called blood typing) to find out the blood group you belong to. The test doesn't take time and is often affordable.