What causes polycythaemia?

Polycythaemia can be divided into several differenttypes, depending on the underlying cause of the condition. In some cases,an underlying cause can't be identified.


"Apparent polycythaemia" is whereyour red cell count is normal, but you have a reduced amount of a fluid called plasma in your blood, making it thicker.

The condition is often caused by being overweight, smoking, drinking excessive amounts of alcoholor taking certain medications such as diuretics. A similar condition that's sometimes called "relative polycythaemia" can also occur as a result of dehydration .

Apparentpolycythaemia may improve if the underlying cause is identified and managed. Stopping smoking or reducing your alcohol intake, for example,may help.

Absolute polycythaemia

"Absolute polycythaemia" is where your body produces too many red blood cells. There are two main types:

  • primary polycythaemia there's a problem in thecells produced by the bone marrow that become red blood cells; the most common type is known as polycythaemia vera (PV)
  • secondary polycythaemia too many red blood cells are produced as the result of an underlying condition

Both PV and secondary polycythaemia are described in more detail below.

Polycythaemia vera (PV)

PV is a rare condition usually caused by a fault in the JAK2 gene, which causes the bone marrow cells to produce too many red blood cells.

The affected bone marrow cells can also develop into other cells found in the blood, which means that people with PV may also have abnormally high numbers of both platelets (thrombocytosis) and white bloods cells (leukocytosis).

Although caused by a genetic fault, PV isn't usually inherited. Most cases develop later in life,with 60 the average age of diagnosis.

Secondary polycythaemia

Secondary polycythaemia is where an underlying condition causes more erythropoietin to be produced. This isa hormone produced by the kidneys thatstimulates the bone marrow cells to produce red blood cells.

Conditions that can cause secondary polycythaemia include:

  • chronic obstructive pulmonary disease (COPD) and sleep apnoea these can cause an increase in erythropoietin, due to not enough oxygen reaching the body's tissues
  • a problem with the kidneys such as a kidney tumour or narrowing of the arteries supplying blood to the kidneys
Content supplied by the NHS Website

Medically Reviewed by a doctor on 21 Dec 2018