Hemoglobin
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.
Also known as: Hgb and Hb
- Male: 13.8 to 17.2 gm/dL
- Female: 12.1 to 15.1 gm/dL
- Anemia (various types)
- Bleeding
- Destruction of red blood cells
- Leukemia
- Malnutrition
- Nutritional deficiencies of iron, folate, vitamin B12, vitamin B6
- Overhydration
- Congenital heart disease
- Cor pulmonale
- Dehydration
- Erythrocytosis
- Low blood oxygen levels (hypoxia)
- Pulmonary fibrosis
- Polycythemia vera
- Anemia of chronic disease
- Drug-induced immune hemolytic anemia
- Giant cell (temporal, cranial) arteritis
- Hemoglobinopathies
- Hemolytic anemia due to G6PD deficiency
- Idiopathic aplastic anemia
- Idiopathic autoimmune hemolytic anemia
- Immune hemolytic anemia
- Iron deficiency anemia
- Paroxysmal cold hemoglobinuria (PCH)
- Paroxysmal nocturnal hemoglobinuria (PNH)
- Pernicious anemia
- Placenta abruptio
- Polymyalgia rheumatica
- Secondary aplastic anemia
- Excessive bleeding
- Fainting or feeling light-headed
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
Definition
Hemoglobin is a protein in red blood cells that carries oxygen. A blood test can tell how much hemoglobin you have in your blood.
See also: Hemoglobin electrophoresis
How the test is performed
Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.
Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.
Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.
How to prepare for the test
No special preparation is necessary.
How the test will feel
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the test is performed
The hemoglobin test is almost always done as part of a complete blood count (CBC).Normal Values
Normal results vary, but in general are:
Note: gm/dL = grams per deciliter
Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
What abnormal results mean
Lower-than-normal hemoglobin may be due to:
Higher-than-normal hemoglobin may be due to:
Additional conditions under which the test may be performed:
What the risks are
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
References
Zuckerman K. Approach to the anemias. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 162.
- Review date:
- February 9, 2010
- Reviewed by:
- David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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