English 3 MIN READ 76 VIEWS May 18, 2024

Unlocking Diversity by Exploring the Various Blood Groups

Written By HealthKart
Medically Reviewed By Dr. Aarti Nehra

A blood group is a classifying system that permits doctors to check whether your blood is compatible or incompatible with another person’s blood. There are four main blood groups: A, B, AB, and O. Blood banks use the presence of A or B antigens on the red blood cells to determine your different types of blood groups. Additionally, they test for the presence of a protein known as the Rh factor. They separate your blood into two groups. They put it in the positive (+) group if you have this protein and the negative (-) group in case you don’t.

This makes for eight common blood types:

  • A positive (A+)
  • A negative (A-)
  • B positive (B+)
  • B negative (B-)
  • AB positive (AB+)
  • AB negative (AB-)
  • O positive (O+)
  • O negative (O-)

Awareness of blood groups helps medical practitioners do safe blood transfusions from one donor to another during a blood transfusion. Organ compatibility between blood types also needs to be considered for organ transplants.

What do Different Blood Types Mean?

For most people, “blood types” will be synonymous with A, B, AB, and O. These letters classify blood types by whether your red blood cells have the A antigen or the B antigen. This is called the ABO system.

  • Type A: The A antigen is present in the red blood cell with anti-B antibodies.
  • Type B: The B antigen is present in RBCs with anti-A antibodies.
  • Type AB: Red blood cells have both A and B type antigens with no antibodies.
  • Type O: Unlike A and B blood types, the red blood cells have no A or B antigens, but have anti A and anti B antibodies. O+ is the most common blood type.

Blood types are either “positive” or “negative” depending on the absence or presence of the D antigen, another marker of the Rh factor. It is called the Rh system. Since RhD positivity is more frequent than RhD negativity, the chances of having RhD-positive babies are relatively higher.

Positive (+): RhD is the antigen present on the surface of the red blood cell.

Negative (-): Red blood cells are without RhD antigen.

Rarest Blood Types

Furthermore, there are more than 600 antigens that may bind to the red blood cells in addition to the ABO system. More than 30 different blood group systems can be related to these unique antigens. Other blood group systems may include –

  • Duffy blood group
  • The antigen K (Kell group)
  • Lutheran blood group
  • Kidd blood group

These blood types are not expected. The most common definition of a rarest blood type is the type of blood group that occurs at a frequency of 1 in 1,000 people or fewer.

The Rh-null blood type is one of the rarest in the world. Only about 50 persons on Earth are known to have this blood type. It is the rarest type of blood, with a frequency of only one in 500,000 people. It is counted as precious blood as there are only 9 active donors across the world. This is why it is sometimes called “golden blood.”

Which Blood Types are Safe to Transfuse Between Patients?

One of the essential aspects of blood donation is checking whether the recipient and the donor are compatible regarding blood types. If you are provided with blood that contains antigens your body has no idea of, then your immune system may attack the donated blood cells. Such an outcome could be fatal.

A blood group chart  lets doctors determine which blood types are safe for your blood to receive. They can quickly identify the people who are eligible to accept your blood donation.

A positive: If you are A positive, then you can get blood that’s A positive, A negative, O positive, or O negative.

A negative: You may receive A negative or O negative blood, the universal blood type.

B positive: You may receive the blood of B positive, B negative, O positive, and O negative, respectively.

B negative: You may get B negative blood or O negative blood.

AB positive: You can be a universal donor for any blood type.

AB negative: This is blood that is AB negative, A negative, B negative, or O negative.

O positive: You can be given with O positive or O negative blood.

O negative: You can receive only the O negative blood group.


It is important to know your blood group. You should first find your blood type if you ever require a blood transfusion. Knowing which blood types are compatible with yours enables your doctor to keep you safe, particularly when you need blood. 

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