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Hemoglobin
- Overview & Description
- Preparation & Expectations
- Results and Values
- Attribution
- What is hemoglobin?
- How is hemoglobin measured?
- What are normal hemoglobin values?
- What does a low hemoglobin level mean?
- What does a high hemoglobin level mean?
Overview & Description
Hemoglobin is a protein in red blood cells. It carries oxygen from the lungs to cells throughout the body, and carries carbon dioxide from the cells to the lungs. A hemoglobin test measures the level of this protein in a sample of blood.
Who is a candidate for the test?
Often, this test is done as part of a complete blood count, or CBC. Or it may be done:
How is the test performed?
Blood for the test is usually taken from a person's forearm. First, a tight band is put on the upper arm to make the veins swell below it. An area of skin on the forearm over the vein chosen is cleansed. Then a needle is inserted into the vein and a sample of blood is collected in a tube.
Occasionally blood is taken from another site, such as a finger or heel. If so, the skin is cleansed and pricked with a sharp tool called a lancet. Drops of blood are collected in a tiny tube. The blood is analyzed at a lab.
Preparation & Expectations
What is involved in preparation for the test?
Generally, no preparation is needed.
Results and Values
What do the test results mean?
Age, sex, and other factors cause normal ranges for hemoglobin to vary. Generally, healthy test ranges are:
Low values of hemoglobin generally mean that a person has a low red blood cell count, which is also called anemia. Anemia has many possible causes. Common causes include:
Increased hemoglobin levels can occur for several reasons. Common causes include:
Depending on the results of this test and the suspected cause of the results, the healthcare provider may suggest a treatment or further tests.
Attribution
Author:Francesca Coltrera, BA
Date Written:
Editor:Evans, Gwen, BA
Edit Date:04/23/00
Reviewer:Adam Brochert, MD
Date Reviewed:09/24/01
Sources
Anderson KN, Anderson LE, Glanze WD. Mosby's medical, nursing, and allied health dictionary, 5th ed. St. Louis, Missouri: Mosby-Year Book, Inc., 1998.
Miller BF, Keane, CB. Encyclopedia and dictionary of medicine, nursing, and allied health, 4th ed. Philadelphia, Pennsylvania: WB Saunders Company, 1987.
Mosby's manual of diagnostic and laboratory tests. Kathleen D. Pagana and Timothy J. Pagana. St. Louis: Mosby, 1998. (256)
Report of the U.S. Preventive Services Task Force. Guide to clinical preventive services, 2nd ed. Alexandria, Virginia: International Medical Publishing, 1996.
What is hemoglobin?
What is hemoglobin?
Hemoglobin is the protein molecule in red blood cells that carries oxygen from the lungs to the body's tissues and returns carbon dioxide from the tissues to the lungs. The iron contained in hemoglobin is responsible for the red color of blood.
How is hemoglobin measured?
How is hemoglobin measured?
Several methods exist for measuring hemoglobin, most of which are done currently by automated machines designed to perform several different tests on blood. Within the machine, the red blood cells are broken down to get the hemoglobin into a solution. The free hemoglobin is exposed to a chemical containing cyanide which binds tightly with the hemoglobin molecule to form cyanmethemoglobin. By shining a light through the solution and measuring how much light is absorbed (specifically at a wavelength of 540 nanometers), the amount of hemoglobin can be determined.
What are normal hemoglobin values?
What are normal hemoglobin values?
The hemoglobin level is expressed as the amount of hemoglobin in grams (gm) per deciliter (dl) of whole blood, a deciliter being 100 milliliters.
The normal ranges for hemoglobin depend on the age and, beginning in adolescence, the sex of the person. The normal ranges are:
- Newborns: 17-22 gm/dl
- One (1) week of age: 15-20 gm/dl
- One (1) month of age: 11-15gm/dl
- Children: 11-13 gm/dl
- Adult males: 14-18 gm/dl
- Adult women: 12-16 gm/dl
- Men after middle age: 12.4-14.9 gm/dl
- Women after middle age: 11.7-13.8 gm/dl
All of these values may vary slightly between laboratories. Some laboratories do not differentiate between adult and "after middle age" hemoglobin values.
What does a low hemoglobin level mean?
What does a low hemoglobin level mean?
A low hemoglobin is referred to as being anemic. There are many reasons for anemia. Some of the more common reasons are loss of blood (traumatic injury, surgery, bleeding colon cancer), nutritional deficiency (iron, vitamin B12, folate), bone marrow problems (replacement of bone marrow by cancer, suppression by chemotherapy drugs, kidney failure), and abnormal hemoglobin (sickle cell anemia).
What does a high hemoglobin level mean?
What does a high hemoglobin level mean?
Higher than normal hemoglobin levels can be seen in people living at high altitudes and in smokers. Dehydration produces a falsely high hemoglobin which disappears when proper fluid balance is restored. Some other infrequent causes are lung disease, certain tumors, a disorder of the bone marrow known as polycythemia rubra vera, and abuse of the drug erythropoietin (Epogen) by athletes for blood doping purposes.