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?
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?
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?
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?
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.

What causes a low hemoglobin count?
Hemoglobin is the iron-rich protein in red blood cells that gives blood its red color. The normal range of hemoglobin is approximately 14 to 17 grams per deciliter for men and 12 to 16 grams per deciliter for women. A low hemoglobin count indicates a low red blood cell count (anemia). Anemia can have many causes, including:
- Vitamin and iron deficiencies
- Acute or chronic bleeding
- Hormone deficiencies, such as thyroid hormone or testosterone
- Chronic diseases, such as kidney failure, cancer and Crohn's disease
- Autoimmune diseases, such as lupus
- Side effect of certain medications, such as chemotherapy drugs

Treatment depends on the underlying cause.