There are four main blood types A, B, AB and O in the ABO blood group system.
Manufactured in the bone marrow, red blood cells are continuously being produced and broken down. They live for approximately 120 days in the circulatory system and are eventually removed by the spleen.
Patients who benefit most from transfusions of red cell components include those with chronic anaemia resulting from disorders such as kidney failure, malignancies or gastrointestinal bleeding and those with acute blood loss resulting from trauma or surgery.
Donated red cell components normally have a life of 35 days or may be treated and frozen for extended storage for up to 10 years.