Polycythaemia vera (PV) is a rare blood cancer that affects the bone marrow. It is sometimes called erythrocytosis which means too many red blood cells.
It is one of a group of conditions called myeloproliferative neoplasms or myeloproliferative disorders.
Find out about polycythaemia vera, including risks and causes and possible symptoms.
The first test to diagnose polycythaemia vera is usually a blood test. Read about the tests to diagnose and the treatment you might have.
Find information on research into polycythaemia vera and read about organisations and resources that can help you cope.