How is the blood cancer diagnosed?
The condition is often picked up by tests aimed at counting the amount of space the red blood cells take up in the blood.
Doctors will also diagnose the disease based on the signs and symptoms, age, overall health, and medical history.
The main signs health practitioners look for during examination are an enlarged spleen, red skin on the face and bleeding from the gums.
As the disease causes blood to thicken, the NHS explains this may also cause:
High blood pressure.