ABO Blood Components

Human blood is made up of many different and specialized cells that are suspended in a solution or fluid. Blood carries oxygen and nourishment to the cells of our body and removes waste products. This process involves many of our organs such as our heart, kidney, liver, spleen and lungs.

Human blood types are categorized into "systems" that are determined by a combination of substances on the surface of the red blood cell as well as the presence or absence of proteins in the fluid part of your blood. The two main blood group systems are the ABO and Rhesus (Rh) systems.

What determines which group you belong to depends on the presence or absence of "antigens" on the surface of your red blood cells and also the presence or absence of "antibodies" in the fluid part of your blood.

In the ABO system there are four possible types: A, B, O and AB. In the Rhesus system, you are either Rh Positive (+) or Negative (-) depending on the presence or absence of the "D antigen".

Compatibility of blood types
The table below outlines donor/recipient compatibilities.

You will notice that the type O Rh NEG person can give blood to anyone. It is the blood type used in emergency situations. People with type AB Rh POS blood can receive blood from any other blood type. However, in most cases, recipients receive blood from a donor in their own group. In other words, a person with type A Rh POS blood will receive blood from a donor who also has A Rh POS blood.

Blood Compatibility

Patient Type

 Compatible Red Cell Types

Compatible Plasma Types


 A / O

 A / AB


B / O

  B / AB


O / A / B / AB

A / B 

 AB / A / B / O


Rh Pos

 Rh Pos / Rh Neg

Rh Neg 

Rh Neg


Distribution of blood types in Canada
You will see from the table below that some blood groups are more common than others. Also, in different countries one blood group may also be more common in one country than another country. 

Rhesus positive
(Rh POS) : 85 %  

Rhesus negative
(Rh NEG) : 15 %


Group O: 46% 

 O POS : 39%

O NEG : 7%

Group A: 42% 

A POS : 36%

A NEG : 6%

Group B: 9% 

B POS : 7.5%

B NEG : 1.5%

Group AB: 3 % 

AB POS : 2.5%

AB NEG : 0.5%