RBC Count
Overview
RBC count measures the number of red blood cells (erythrocytes) per unit volume of blood, typically reported as millions per microliter. Red blood cells contain hemoglobin and transport oxygen from lungs to tissues while removing carbon dioxide. Elevated counts (polycythemia) may indicate dehydration, smoking, high altitude, or polycythemia vera, while low counts (anemia) suggest blood loss, nutritional deficiencies, hemolysis, or bone marrow disorders; it is clinically useful for diagnosing anemia types, monitoring chronic disease response, and assessing overall oxygen-carrying capacity.
Clinical Use Cases
- Diagnosing and classifying anemia (iron deficiency, vitamin B12/folate deficiency).
- Evaluating polycythemia and erythrocytosis causes.
- Monitoring chemotherapy effects on bone marrow function.
- Assessing blood loss, hemolysis, or response to erythropoietin therapy.
- Preoperative screening and sports medicine evaluations.
Specimen Types
- Whole blood (EDTA anticoagulant, lavender top tube).
- Capillary blood (fingerstick).
Measurement Methods
- Automated hematology analyzers (impedance, flow cytometry).
- Manual counting with hemocytometer (rarely used).
- Point-of-care analyzers.
Test Preparation and Influencing Factors
- No fasting required.
- Avoid dehydration or recent high-altitude exposure.
- Recent blood transfusion or donation affects results.
- Posture (supine vs. standing) influences plasma volume.
- Hemolysis or clotted samples cause inaccurate counts.
Synonyms
- Erythrocyte count.
- Red cell count.
- RBC.