Erythrocytosis

Last updated Nov. 1, 2025, 6:27 a.m. by ivo

The haemoglobin, haematocrit and red blood cell count reference ranges will vary depending on the age, gender and pregnancy status of the patient, as well as the laboratory performing the test. In general, a haemoglobin > 165 g/L in males and >145 g/L in females; and a haematocrit > 0.5 in males and > 0.44 in females is considered elevated.

An elevated haematocrit should be demonstrated on more than one occasion to ensure the change is not artefactual.

Primary erythrocytosis

Seen in polycythaemia vera.
The increased red cell production is independent of EPO levels.
Usually related to an acquired genetic mutation which drives EPO-independent erythropoiesis (>95% have the JAK2 V617 mutation).

Secondary erythrocytosis

Secondary erythrocytosis is seen in a range of medical conditions and can be related to hypoxia (due to compensatory increases in EPO production) or inappropriate EPO production.

Common causes include:

Smoking
Chronic lung diseases
Obstructive sleep apnoea and obesity hypoventilation syndrome
Androgen administration
Cirrhosis
Cyanotic heart disease

Rare causes include

High affinity haemoglobins
EPO secreting tumours including hepatocellular carcinomas; renal cell carcinomas; phaeochromocytomas; and carcinoma/adenoma of the adrenals, ovary, lung, thymus and parathyroid glands, Uterine fibroids

Further evaluation

Peripheral blood testing for JAK2 V617F mutation
If the JAK2 mutation testing is negative polycythaemia vera is unlikely and investigations should be directed at secondary causes (smoking; COPD e.g. RFTs, O2 saturation or ABG; sleep apnoea e.g. sleep study).
Venesection is not recommended for secondary polycythaemia. The mainstay of management is in management of the underlying cause.

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When To Refer

Positive JAK2 mutation testing
Persistent erythrocytosis in JAK2 mutation negative non-smokers with a normal sleep study and no other apparent secondary cause

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