Blood is grouped according to their types, specifically the presence and absence of antigens; substances that may trigger immune response and antibody, a protein found in plasma and responsible for the body’s natural defense. Blood groups are categorized into two: ABO (A, B, AB, and O) and Rh (either RhD positive or RhD negative).
#1 – The ABO system
Under the ABO system, there are four main blood groups. These include the following:
- Group A – It has an A antigen on red blood cells and anti-B antibody in the plasma.
- Group B – It has a B antigen and an anti-A antibody in the plasma.
- Group AB – It has both antigens A and B, but it does not have any antibody.
- Group O – It has both anti-A and anti-B antibodies in the plasma. However, it does not have any antigens. (1, 2, 3, and 4)
The most common blood group is O. It is important to categorize the blood according to their group, especially in the case of blood transfusion. Receiving the wrong ABO group can be life-threatening. Those with blood type A should not give blood to people with type B and vice versa. Those with blood type O can donate to people with any blood type. However, people with O blood should only receive O blood and nothing else. (2, 3)
Refer to the table below for a detailed summary of the ABO system.
Donor red cell type
Donor plasma type
A or O
A or AB
B or O
B or AB
Both A and B antigen
AB, B, A, and O
Both anti-A and anti-B
O, A, B, and AB
- Blood Group O – It is the most common blood type, particularly in South and Central America.
- Blood Group B – It is the most prevalent blood type in Asia, particularly in Northern India.
- Blood Group A – It is the most common blood type across the globe, but the frequency is higher among Australian Aboriginal people and Sami people.
- Blood Group AB – The percentage of people with blood type AB is low. It is common in the sub-continental Indian population. (3, 4, and 5)
The Rh (Rhesus Factor) System
Red blood cells can sometimes have another antigen; RhD antigen, which is a type of protein inherited from the parent. If such a protein is present, then you belong to the RhD positive group. If it is absent, then you belong to the RhD negative group. There are eight blood groups in the RhD system. These are the following:
- A+ – A RhD positive
- A- – A RhD negative
- B+ – B RhD positive
- B- – B RhD negative
- O+ – O RhD positive
- O- – O RhD negative
- AB+ – AB RhD positive
- AB- – AB RhD negative (1, 2)
Refer to the table below for a detailed explanation on how Rhesus factor is inherited.
Rh Factor of the mother
Rh factor of the father
Rh factor of the baby
Could be Rh+ or Rh-
Could be Rh+ or Rh-
In case of emergency, blood type O either RhD negative and positive can be given to anyone regardless of the blood type, especially if the blood type of the patient is unknown.
Around 80% of the total population in the United States are RhD positive. AB is the rarest blood type.
Testing for Blood Groups
To find out your blood group, a blood typing procedure has to be done. Your blood’s red blood cell is mixed with different antibody solutions. If the solution has anti-B antibodies and you have B antigens, the blood will clump together. If the blood didn’t react to anti-A and B antibodies, then you are blood group O. Basically, various types of antibodies have to be used to find out your blood group. (4, 5, and 6)
The significance of blood typing
The body is protected against invaders through the immune system. It has the ability to identify antigens. Blood typing is done in order to get a blood transfusion safely. The immune system has to recognize the donor cells; meaning, the donor cell should match that of the receiver. If it is not a match, the immune system will reject it. The antibody will do its best to destroy the invading cells causing you to have a fever, chills, and low blood pressure. In severe cases, it causes kidney failure and breathing problems. (5, 6)
Giving and receiving blood should be based on the following principles:
- Blood Type O – If your blood type is O, you can donate blood to anyone. However, you can only receive blood from type O individuals.
- Blood Type A – If your blood type is A, you can donate blood to type A and type AB individuals. On the other hand, you can only receive blood from people with type A and type O blood.
- Blood Type B – You can donate blood to individuals whose blood type is B and AB. However, those with type B blood can only receive blood from type B and type O individuals.
- Blood Type AB – If your blood type is AB, you can only donate blood to people with AB blood type. Fortunately, you can receive blood of any types. (4, 5, 6, and 7)
Blood Type AB is the universal receiver and blood type O is the universal donor.
See the table below.
A, B, AB, and O
O, A, B, and AB
The table below shows how a child inherits his/her blood type.
|Parent 1 blood type||AB||AB||AB||AB||B||A||A||O||O||O|
|Parent 2 blood type||AB||B||A||O||B||B||A||B||A||O|
|Possible Child blood type||A, B, AB||A, B, AB||A, B, AB||A, B||O, B||O, A, B, AB||A, O||O, B||O, A||O|
When is blood group important?
- Blood donation/receiving blood transfusion – determining the person’s blood group is important when it comes to donating and receiving blood.
- Pregnancy – Blood grouping in pregnancy is important as it helps in distinguishing the RhD type between the mother and the fetus. If the mother is RhD negative and the fetus is RhD positive, there is some risk involved. The plasma of the mother might create anti-RhD through the process called sensitization. It attacks the red blood cell of the fetus causing jaundice and brain damage, especially if left undetected. If the RhD of the mother and the fetus is not compatible, an injection of anti-D immunoglobin G is a must. This is to prevent the mother’s own production of antibody and reduce the possibility of sensitization. The anti-D immunoglobin is given at 28 weeks and 34 weeks of pregnancy respectively.
- Detect possible fetal risk – Blood testing can help detect a possible health risk in the fetus. (6, 7, 8, and 9)
Who can donate blood?
Not everyone can donate blood. To be able to donate blood, you should meet the following requirements:
- Fit and healthy
- Should be at least 50 kilograms
- 17 to 66 years old
What to keep in mind?
- Blood type O+ is the most common blood type.
- Blood type O- donors are universal donors.
- Blood type A+ is the second most common blood type.
- Blood A- is the universal platelet type.
- Blood type B+ consists 8% of donors and there is always a need for type B+ blood.
- Only 2% of donors are B+, which makes it one of the rarest blood types.
- About 2% of donors are AB+.
- The rarest blood type is AB-. (2, 5, and 9)
Did you know?
- Blood type is inherited.
- Some blood types are common in some countries.
- Blood type has something to do with a person’s personality. Those with type A blood are calm and trustworthy. Those with type B blood are creative and excitable. Those with type AB are emotional and thoughtful. Those with type O blood are leader materials.
- The donor blood is tested for conditions like hepatitis, HIV, syphilis, and West Nile virus.
- In the United States, there are 9.5 million blood donors and about 5 million patients receive blood on a yearly basis.
- Your blood type can predict your susceptibility for some diseases. Those with type O blood are less susceptible to heart disease but are at risk for stomach ulcers. People with type A blood are susceptible to microbial infections but have a higher fertility rate. Those with type AB blood have an increased chance of developing pancreatic cancer.
- Different blood types react differently to stress. Blood type A has a high level of cortisol, a stress hormone, causing them to respond more to stressful situations. People with type O blood tend to have a fight or flight response to stress. They take so much time to recover from stress.
- The bacteria in the gut have something to do with the blood type. Blood type A tends to break down carbohydrates more when compared to blood type O.
- Group O negative blood can donate to other blood types in case of emergency. About 7% of the total population in the world has O negative blood.
- Those with O negative blood have a strong immune system, which corresponds to their long life span.
- O negative blood group disadvantages include susceptibility to thyroid disease and ulcers.
- Your nutritional needs are dependent on your blood type. Blood type O needs more animal protein and less on grains and dairy products. Type A blood needs a vegetarian diet; foods that are pure, fresh, and organic. The reason for this is that type A individuals are prone to diabetes, heart disease, and cancer. Those with type B blood are lucky because they have a strong immune system. They can resist chronic degenerative diseases. People with type AB blood requires a combination of type A and B diet. (2, 5, 8, 9, and 10)
The blood group/blood type of a person depends on the genes he/she inherits from the parents. Antibodies determine blood type too. Antibodies are protein in the blood that fights off foreign substances like germs. Blood typing is important as being given a wrong type of blood can be extremely dangerous. If you happen to receive the wrong blood, it could lead to ABO blood incompatibility. Your immune system treats it as something foreign and attacks it in an attempt to protect your body. Mother and the baby inside her womb may have an incompatible blood type too. To prevent complications, the mother needs to receive treatment during the course of pregnancy. Donating blood is one of the significances of blood typing/blood grouping. Blood donation is used to treat different types of diseases. Someone else’s life can be saved through blood donation. (1, 3, 6, and 10)