Functions and diseases of red and white blood cells.

Red and white blood cells have two main functions: the carriage of oxygen; and defence against microbial attack. The full blood count is one of the most frequently requested routine blood tests; it provides key indices such as haemoglobin and the number of white cell subsets, and provides information to aid diagnosis of a range of conditions, including anaemia, infection, leukaemia, myeloma and lymphoma.