What's Your Type

The differences in human blood are due to the presence or absence of certain protein molecules called antigens and antibodies. The antigens are located on the surface of the red blood cells and the antibodies are in the blood plasma. Individuals have different types and combinations of these molecules. The blood group you belong to depends on what you have inherited from your parents.


To date, more than 20 genetically determined blood group systems exist, but the AB0 and Rh systems are the most important ones used for blood transfusions. Not all blood groups are compatible with each other. Mixing incompatible blood groups leads to blood clumping or agglutination, which is dangerous for individuals.


Nobel Laureate Karl Landsteiner was involved in the discovery of both the AB0 and Rh blood groups.


Rh Factor blood grouping system


Many people also have a so-called Rh factor on the red blood cell's surface. This is also an antigen and those who have it are called Rh+. Those who haven't are called Rh-. A person with Rh- blood does not have Rh antibodies naturally in the blood plasma (as one can have A or B antibodies, for instance). But a person with Rh- blood can develop Rh antibodies in the blood plasma if he or she receives blood from a person with Rh+ blood, whose Rh antigens can trigger the production of Rh antibodies. A person with Rh+ blood can receive blood from a person with Rh- blood without any problems.


AB0 blood grouping system


According to the AB0 blood typing system there are four different kinds of blood types: 

A, B, AB or O. 



Group A


If you belong to Group A blood, you have A antigens on the surface of your red blood cells and B antibodies in your blood plasma. 


Distribution of blood groups among blood donors in South Africa:

A Positive- 32%

A Negative- 5%


Group B


If you belong to the Blood Group B, you have B antigens on the surface of your red blood cells and A antibodies in your blood plasma.


Distribution of blood groups among blood donors in South Africa:

B Positive- 12 %

B Negative- 2%


Group AB


If you belong to the blood group AB, you have both A and B antigens on the surface of your red blood cells and no A or B antibodies at all in your blood plasma.


People with AB positive blood types are the “universal recipients” as they can receive blood from all blood groups. 


Distribution of blood groups among blood donors in South Africa:

AB Positive- 3%

AB Negative- 1%


Group O


If you belong to the blood group O, you have neither A or B antigens on the surface of your red blood cells, but you have both A and B antibodies in your blood plasma.


O Negative blood can be given to anyone in an emergency and O Negative donors are known as the “Universal donors”.


Distribution of blood groups among blood donors in South Africa:

O Positive-39%

O Negative- 6%

Distribution of blood groups in South Africa


The general distribution of blood groups in South Africa is detailed below, although it may vary slightly in different regions. If you have Group O blood, you share a blood type with nearly half the population.


Blood type % how many have it?

O+ 39% one in 3 

O- 7% one in 17 

A+ 32% one in 3 

A- 5% one in 20 

B+ 12% one in 8 

B- 2% one in 50 

AB+ 3% one in 33 

AB- 1% one in 100


What does your blood comprise of and what is it used for?


Blood Products

Blood is vital to human life. It carries essential nourishment to all the tissue and organs of the body. Without it, the tissues will die. The average person has 25 billion red blood cells and, in a normal healthy person, cells are constantly regenerated in the body. Without the protection of blood, no child could be born.


In the womb, the mother's blood ensures that the foetus is supplied with oxygen and nutrients and benefits from the mother's inbuilt defences against disease.


About 45% of the total volume of blood is made up of: 


Red blood cells

White blood cells 



Red blood cells carry oxygen. The haemoglobin, which gives blood its red colour, is the agent that needs to be present for oxygen to be taken up from the lungs. Red blood cells also transport carbon dioxide back to the lungs, for expulsion from the body. Iron is the key factor in the manufacture of haemoglobin. When iron supplies are deficient, people become anaemic, with a corresponding loss of oxygen-carrying ability.


White blood cells defend the body against disease. They make antibodies and fight infections.


Platelets help to control bleeding by sticking to the injured surfaces of blood vessels, and allowing clotting factors to accumulate at the injury site. Plasma is a fluid which carries all these cells, plus other substances such as proteins, clotting factors and chemicals.

Sometimes, through trauma such as haemorrhage, the volume of blood in the body is reduced to such a level that the body cannot replace it fast enough.


Occasionally, some components of the blood are lacking and do not function correctly, as is the case with haemophilia, where clotting of the blood does not occur. At other times, the bone marrow does not produce sufficient haemoglobin, due to a deficiency of the necessary building blocks.


In most cases, blood and blood components will be transfused to patients. All the different components of blood can be used and each plays an important role in saving the lives of different individuals in the community.


Blood has 4 main components:

• red blood cells;

• white blood cells;

• plasma; and 

• platelets all of which are used by patients in need.

One unit of blood can be separated into components and used to treat up to three patients.


The average healthy person can donate blood 330 times in their life.

The rarest blood type is AB negative – less than 1% of the population.

Human blood is 78% water.