Hemoglobin (Hgb)

Hemoglobin is the active, oxygen-carrying component of red blood cells. 

This protein, when fully oxygenated, is characteristically bright red. Whenever it loses a significant amount of its' oxygen, it turns a dark blue color. It takes about 6 grams of desaturated hemoglobin to cause a noticeable change in color.

Increased in the Presence of:

  • Hemoconcentration
  • COPD (chronic obstructive pulmonary disease)
  • CHF (congestive heart failure)
  • Smokers
  • Pre-eclampsia

Decreased in the Presence of:

  • Anemia
  • Hyperthyroidism
  • Chronic liver disease
  • Hemorrhage
  • Hemolysis:
    • Transfusion reaction
    • Drug/chemical reaction
    • Infection
    • Burns
    • Mechanical disruption (artificial heart valves)
  • Systemic Disease
    • Cancer
    • Lupus
    • Sardoidosis

Special Considerations

  • Carbon monoxide binds to the hemoglobin, rendering it incapable of carrying oxygen, but clinically causes the victims' blood to be bright, cherry-red
  • Smokers typically have elevated hemoglobin levels in response to chronic, low-grade carbon monoxide poisoning and other mild respiratory ailments. Because of the carbon monoxide binding, they may still be functionally anemic, even though their hemoglobin levels look good.
  • Adaptation to high altitudes includes moderate elevation of hemoglobin.
  • During the initial phases of an acute hemorrhage, the hemoglobin levels generally doesn't change very much. Later, as extracellular fluid is mobilized and IV fluids are incorporated, there is a dilutional effect that will lead to a reduced hemoglobin level. This fall in hemoglobin may take several hours to develop.

Normal Values*



Women 12.0-16.0
Pregnancy 10.5-14.0
Newborn 14.0-20.0

*These are general values taken from a variety of sources. The actual normal values may vary from lab to lab and from one type of testing protocol to another.


Source: Operational Medicine 2001,  Health Care in Military Settings, NAVMED P-5139, May 1, 2001, Bureau of Medicine and Surgery, Department of the Navy, 2300 E Street NW, Washington, D.C., 20372-5300

Gynecology and Obstetrics CD-ROM
Volumes 1-6
2004 Edition
Lippincott Williams & Wilkins
Copyright 2004
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