Hemoglobin is the most important component of red blood cells. It is composed of a protein called heme, which binds oxygen. In the lungs, oxygen is exchanged for carbon dioxide.
Abnormalities of an individual's hemoglobin value can indicate defects in the normal balance between red blood cell production and destruction. Both low and high values can indicate disease states.
Update Date 3/3/2013
Updated by: Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, Bethanne Black, Stephanie Slon, and Nissi Wang.