Medical Term for Elevated Hematocrit
The medical term for elevated hematocrit is polycythemia (also called erythrocytosis) 1, 2.
Understanding the Terminology
Polycythemia and erythrocytosis are used interchangeably to describe an elevation in age- and sex-adjusted hematocrit 2. The term specifically refers to increased red cell indices, which can include elevated RBC count, hemoglobin, or hematocrit 1.
Clinical Context and Classification
When you encounter elevated hematocrit, it's critical to understand this represents a finding that requires further classification into:
Primary polycythemia (Polycythemia Vera): A myeloproliferative neoplasm driven by JAK2 mutations causing autonomous red blood cell proliferation 3, 2
Secondary polycythemia: Most commonly due to chronic hypoxia, erythropoietin-stimulating drugs (androgens, SGLT2 inhibitors), or erythropoietin-secreting tumors 2
Relative polycythemia: Results from chronic plasma volume contraction rather than true red cell mass increase 2
Important Clinical Pitfall
The key clinical question when finding polycythemia is whether it reflects a myeloproliferative neoplasm, as this carries risk of thrombotic or hemorrhagic complications and potential progression to myeloid leukemia 1. The WHO diagnostic criteria define polycythemia vera as requiring hemoglobin ≥18.5 g/dL in men or ≥16.5 g/dL in women, or hematocrit values 25% above mean normal predicted value 3.
Most cases seen in general practice represent relative polycythemia or secondary causes rather than true myeloproliferative disease 2. When polycythemia is isolated without leukocytosis or thrombocytosis, secondary and hereditary causes should be investigated first 2.