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Latest Edit: Hector 2014-03-24 (EDT)

See Also Lab Tests

This test is a measure of the total amount of hemoglobin (Hgb) in the blood. It is an indirect measurement of the red blood cell (RBC) count. It is part of the complete blood cell count and is often used in the evaluation of anaemia.[1], [2]


Hemoglobin serves as a vehicle for oxygen and carbon dioxide transport. The oxygen-carrying capacity of the blood is determined by the Hgb concentration. Hgb is also an important acid-base buffer system. Hgb levels closely reflect the hematocrit and RBC values.

Patient Preparation

  • Fasting is not required for this test.

Interfering Factors:

  • Women tend to have lower values than men.
  • Hgb values tend to decrease with age.
  • Hgb levels are highest in the morning and lowest at night.
  • Heavy smokers have higher Hgb levels.
  • Living in high altitudes may increase Hgb levels.
  • Drugs that may cause increased levels include gentamicin and methyldopa.
  • Drugs that may cause decreased levels include antibiotics, antineoplastic drugs, aspirin, indomethacin, rifampin and sulfonamides.

Clinical Implications

Hgb is primarily used as a test for anaemia, but it can also indicate:

High levels indicate:

Low levels indicate:

Associated Tests

A hemoglobin test is typically part of a complete blood count which includes hematocrit and red blood cell count which are closely associated with hemoglobin.


  1. Pagana Kathleen D, Pagana Timothy J (2006) Mosby's Manual of Diagnostic and Laboratory Tests, Mosby.
  2. Weatherby Dicken, Ferguson Scott (2002) Blood Chemistry and CBC Analysis: Clinical Laboratory Testing from a Functional Perspective, Bear Mountain.