What causes it?

There are different types and many causes of polycythaemia.

Polycythaemia is a type of blood disorder characterised by the production of too many red blood cells.

There are many causes of relative and secondary polycythaemia, but the cause of Polycythaemia vera or Primary polycythaemia is not known. There is certainly abnormal functioning of the cells in the bone marrow, but the reason for this remains obscure.

Polycythaemia is a very rare condition, with a tendency to be slightly more common in men and people of Jewish ancestry. There is no cure, but various treatment options are available that will reduce the risk of complications and prolong life.