Siamak T. Nabili, MD, MPH
Dr. Nabili received his undergraduate degree from the University of California, San Diego (UCSD), majoring in chemistry and biochemistry. He then completed his graduate degree at the University of California, Los Angeles (UCLA). His graduate training included a specialized fellowship in public health where his research focused on environmental health and health-care delivery and management.
William C. Shiel Jr., MD, FACP, FACR
Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.
In this Article
- 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?
- What is sickle cell disease?
- What is thalassemia?
- What is the hemoglobin A1c test?
How is hemoglobin measured?
Hemoglobin is usually measured as a part of the complete blood count (CBC) from a blood sample.
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 cyanomethemoglobin. 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 gender of the person. The normal ranges are:
- Newborns: 17 to 22 gm/dL
- One (1) week of age: 15 to 20 gm/dL
- One (1) month of age: 11 to 15gm/dL
- Children: 11 to 13 gm/dL
- Adult males: 14 to 18 gm/dL
- Adult women: 12 to 16 gm/dL
- Men after middle age: 12.4 to 14.9 gm/dL
- Women after middle age: 11.7 to 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 level is referred to as anemia or low red blood count. Lower than normal number of red blood cells is referred to as anemia and hemoglobin level reflects this number. There are many reasons for anemia.
Some of the more common causes are:
- loss of blood (traumatic injury, surgery, bleeding, colon cancer or stomach ulcer),
- nutritional deficiency (iron, vitamin B12, folate),
- bone marrow problems (replacement of bone marrow by cancer),
- suppression by chemotherapy drugs,
- kidney failure, and
- abnormal hemoglobin structure (sickle cell anemia or thalassemia).
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