Hemoglobin

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

A blood sample is needed. For information on how this is done, see: Venipuncture

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 Results

Normal results vary, but in general are:

• Male: 13.8 to 17.2 gm/dL
• Female: 12.1 to 15.1 gm/dL

Note: gm/dL = grams per deciliter

The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples.Talk to your doctor about the meaning of your specific test results.

What Abnormal Results Mean

Lower-than-normal hemoglobin may be due to:

• Anemia (various types)
• Bleeding
• Destruction of red blood cells
• Leukemia
• Malnutrition
• Nutritional deficiencies of iron, folate, vitamin B12, vitamin B6
• Overhydration

Higher-than-normal hemoglobin may be due to:

• Congenital heart disease
• Cor pulmonale
• Dehydration
• Erythrocytosis
• Low blood oxygen levels (hypoxia)
• Pulmonary fibrosis
• Polycythemia vera

Additional conditions under which the test may be performed:

• 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

Risks

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:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

Alternative Names

Hgb; Hb

References

Bunn HF. Approach to the anemias. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 161.