Red blood cells - they are coloured red inside by haemoglobin, which serves to transport oxygen. Red blood cells make up around 40% of the content of blood. Red blood cells are most needed by sick people who have lost blood due to an accident or operation.

Platelets are the smallest blood cells and are responsible for the coagulation process. Platelets are transfused to patients with coagulation problems, leukaemia and cancer, during and after chemotherapy.

 

White blood cells are relatively large and almost colourless. Less numerous than red blood cells, they are able to move. They are responsible for protecting the body against infection.

 

Plasma has a yellow colour, makes up about 55% of the volume of blood and contains many proteins with important functions in the body. It is usually transfused to patients who have lost a lot of blood, with coagulation problems, burns or shock victims, and those with haemophilia or other haemorrhages.