Elevated Hematocrit

An increased hematocrit (Hct), representing the proportion of red blood cell volume relative to total blood volume above the normal reference range (approximately 36-50%), reflecting either increased red cell mass (absolute erythrocytosis) or reduced plasma volume (relative erythrocytosis).

Causes

• Reduced plasma volume (relative erythrocytosis)

  • Dehydration

  • Diuretic therapy

  • Fluid loss (vomiting, diarrhea, excessive sweating)

• Increased red blood cell production (absolute erythrocytosis)

  • Polycythemia vera

  • Secondary erythrocytosis due to hypoxia

    • Tobacco smoke exposure

    • High altitude

    • Obstructive sleep apnea

    • Chronic obstructive pulmonary disease

    • Pulmonary fibrosis

    • Congenital cyanotic heart disease

• Hormonal/medication-related causes

  • Testosterone therapy

  • Exogenous erythropoietin use: Renal tumor