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.
Melissa Conrad Stöppler, MD
Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.
In this Article
- What is the hematocrit?
- How is the hematocrit measured?
- What is a normal hematocrit?
- What does a low hematocrit mean?
- What does a high hematocrit mean?
What is a normal hematocrit?
The normal ranges for hematocrit are depend on the age and, after adolescence, the sex of the individual. The normal ranges are:
- Newborns: 55% to 68%
- One (1) week of age: 47% to 65%
- One (1) month of age: 37% to 49%
- Three (3) months of age: 30% to 36%
- One (1) year of age: 29% to 41%
- Ten (10) years of age: 36% to 40%
- Adult males: 42% to 54%
- Adult women: 38% to 46%
These values may vary slightly among different laboratories.
What does a low hematocrit mean?
A person who has a low hematocrit 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, and 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).
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What does a high hematocrit mean?
Higher than normal hematocrit levels represent abnormally elevated red blood cell counts. High hematocrits can be seen in people living at high altitudes and in chronic smokers. Dehydration produces a falsely high hematocrit that disappears when proper fluid balance is restored. Some other infrequent causes of an elevated hematocrit 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.
Medically reviewed by Avrom Simon, MD; Board Certified Preventative Medicine with Subspecialty in Occupational Medicine
Braunwald, Eugene, et al. Harrisons's Principles of Internal Medicine. 17th ed. McGraw-Hill, 2008.
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