Hemoglobin

Overview

Hemoglobin measures the oxygen-carrying iron-containing protein within erythrocytes that reversibly binds oxygen in the lungs and delivers it to tissues. It exists primarily as HbA (α2β2 tetramers) in adults, with variants like HbF and HbA2 having diagnostic significance. Low levels (anemia) indicate blood loss, hemolysis, nutritional deficiency, or bone marrow failure, while high levels (polycythemia) suggest chronic hypoxia or myeloproliferative disorders. Hemoglobin is clinically essential for classifying anemia severity, guiding transfusion decisions, and monitoring chronic disease response.

Clinical Use Cases

  • Diagnosing and classifying anemia (iron deficiency, thalassemia, sickle cell).
  • Monitoring response to anemia therapy and blood loss.
  • Evaluating polycythemia (primary vs secondary).
  • Assessing acute blood loss and perioperative status.

Specimen Types

  • Whole blood (EDTA, heparin, or citrate).
  • Capillary blood (point-of-care).

Measurement Methods

  • Automated hematology analyzer (spectrophotometric cyanide-free method).
  • Hemoglobinometer (point-of-care).
  • Manual cyanmethemoglobin method (reference).

Test Preparation and Influencing Factors

  • No fasting required.
  • Hemolysis, lipemia, or icterus interfere with spectrophotometric methods.
  • High WBC or platelet counts cause pseudohyperhemoglobinemia.
  • Recent transfusion or erythropoietin therapy alters levels.

Synonyms

  • Hgb.
  • Hb.

Further Reading

  • Hemoglobin Test; MedlinePlus;