Hemoglobin (Hb)

What it measures

Measures the concentration of hemoglobin, the oxygen-carrying protein inside red cells. It is the key value used to detect and grade anemia or polycythemia and is part of every complete blood count.

Specimen and preparation

• Specimen: Whole blood (EDTA)
• Tube: Lavender top
• Preparation: No fasting needed. Mix the tube gently 8–10 times; avoid prolonged tourniquet use and drawing above an IV line.

Reference range

Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.

Causes of high values

• Dehydration or hemoconcentration
• Polycythemia vera
• Chronic hypoxia (lung disease, high altitude, smoking)
• Erythropoietin-secreting tumors or EPO/testosterone use

Causes of low values

• Iron deficiency and other nutritional anemias
• Acute or chronic blood loss
• Hemolysis
• Chronic kidney disease or chronic inflammation
• Bone marrow failure or infiltration

Method

Automated hematology analyzer (SLS-hemoglobin or cyanmethemoglobin photometry)

Good to know

Multiply g/dL by 10 for g/L. Values below about 7 g/dL are often treated as critical. Marked lipemia or very high WBC counts can falsely raise results.

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