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Medical Author:

Siamak T. Nabili, MD, MPH

Siamak T. Nabili, MD, MPH

Dr. Nabili received his undergraduate degree from the University of California, San Diego (UCSD), majoring in chemistry and biochemistry. He then completed his graduate degree at the University of California, Los Angeles (UCLA). His graduate training included a specialized fellowship in public health where his research focused on environmental health and health-care delivery and management.

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Medical Editor:

Charles Patrick Davis, MD, PhD

Charles Patrick Davis, MD, PhD

Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

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In this Article

• What is polycythemia?
• What are normal ranges of hematocrit, red cell counts, and hemoglobin?
• What causes polycythemia?
• What are the causes of primary polycythemia?
• What are the common causes of secondary polycythemia?
• Can other sources of erythropoietin (EPO) cause polycythemia?
• What is relative polycythemia?
• What is stress polycythemia?
• What are the risk factors for polycythemia?
• What are the symptoms of polycythemia?
• When should I see a doctor about polycythemia?
• How is polycythemia diagnosed?
• What is the treatment for polycythemia?
• What are the complications of polycythemia?
• Can polycythemia be prevented?
• What is the outlook (prognosis) for polycythemia?
• Polycythemia At A Glance
• Patient Comments: Polycythemia (High Red Blood Cell Count) - Cause
• Patient Comments: Polycythemia - Experience
• Patient Comments: Polycythemia - Symptoms
• Find a local Hematologist in your town
• Polycythemia (High Red Blood Cell Count) Index

Hematocrit is the ratio of the volume of red cells to the volume of whole blood. The normal range for hematocrit varies between sexes and is approximately 45% to 52% for men and 37% to 48% for women.

Red cell count signifies the number of red blood cells in a volume of blood. The normal range in men is approximately 4.7 to 6.1 million cells/ul (microliter). The normal range in women range from 4.2 to 5.4 million cells/ul, according to NIH (National Institutes of Health) data.

Hemoglobin is a protein in the red blood cells that carries oxygen and gives blood its red color. The normal range for hemoglobin may differ between the sexes and is approximately 13 to 18 grams per deciliter for men and 12 to 16 grams per deciliter for women.

Causes of polycythemia are primary or secondary. In primary polycythemia, intrinsic factors in red blood cell production cause an increase in red cell count. In secondary polycythemia, external factors result in polycythemia.

Primary polycythemias are due to acquired or inherited genetic mutations causing abnormally high levels of red blood cell precursors. Primary familial and congenital polycythemia (PFCP) and polycythemia vera (PV) are in this category.

Polycythemia vera is a rare condition occurring only in about one person per one million in the United States. Polycythemia vera is typically associated with an elevated white blood cell count (leukocytosis) and platelet count (thrombocytosis). An enlarged spleen (splenomegaly) and low erythropoietin levels are other clinical features of polycythemia vera.

Until recently, the exact mechanism of polycythemia vera was not well understood. In 2005, genetic mutations of the JAK2 gene were found to be responsible for most cases of polycythemia vera. These mutations are thought to possibly increase the sensitivity of the red blood cell precursors to erythropoietin, thereby, increasing red blood cell production.

Primary familial and congenital polycythemia (PFCP) is also thought to be caused by genetic mutations resulting in increased responsiveness to normal levels of erythropoietin. Most cases are caused by different mutations to the EPOR gene.