Hematocrit (Hct) — Normal Range & Interpretation
Hematocrit measures the percentage of whole blood volume occupied by red blood cells. It reflects red cell mass and plasma volume together, making it a core component of the CBC for evaluating anemia, polycythemia, and hydration status. Hct tracks closely with hemoglobin and runs approximately three times the hemoglobin value in stable patients.
| Male | Female | Unit | Category |
|---|---|---|---|
| 42–52% | 37–47% | % | CBC / Hematology |
Clinical Context
Hematocrit measures the percentage of whole blood volume occupied by red blood cells. It reflects red cell mass and plasma volume together, making it a core component of the CBC for evaluating anemia, polycythemia, and hydration status. Hct tracks closely with hemoglobin and runs approximately three times the hemoglobin value in stable patients.
Elevated hematocrit points to polycythemia vera, chronic hypoxia from COPD or sleep apnea, high-altitude residence, testosterone therapy, or dehydration that concentrates red cells. Depressed hematocrit signals iron deficiency, chronic blood loss from GI or menstrual sources, chronic kidney disease with low erythropoietin, bone marrow suppression, hemolysis, pregnancy-related hemodilution, or acute hemorrhage once fluid shifts equilibrate.
On the AANP exam, expect questions on the Hct-to-Hgb 3:1 relationship and recognition of when values break that ratio. Questions frame Hct alongside MCV to classify anemia as microcytic, normocytic, or macrocytic and to trigger iron studies, B12, or folate workup. Expect scenarios distinguishing true polycythemia from hemoconcentration in a dehydrated patient, identifying occult GI bleeding in an older adult with a falling Hct, and recognizing physiologic dilutional anemia of pregnancy rather than pathology requiring intervention.
Practice Questions
A 48-year-old female presents for an annual physical. Her CBC reveals Hgb 14.0 g/dL and Hct 42%. Which interpretation of this hematocrit value is most accurate?
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