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What Is a Normal Level of Alkaline Phosphatase?

author image Leann Mikesh, Ph.D.
Leann Mikesh holds a Ph.D. in pathology. She has trained at the University of Virginia Medical Laboratories and has over 15 years experience in clinical, cancer and immunology research. Dr. Mikesh performed kidney and bone marrow transplantation compatibility testing to put herself through graduate school.
What Is a Normal Level of Alkaline Phosphatase?
Alkaline phosphatase tests for liver or bone disease. Photo Credit: Alexander Novikov/iStock/Getty Images

Alkaline phosphatase is an enzyme found in many organs, including the liver, bone, kidney, intestine and placenta. The highest concentration of alkaline phosphatase comes from the liver and bone. A routine blood test detects the total amount of alkaline phosphatase in the blood.

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Significance of Alkaline Phosphatase

Alkaline phosphatase is typically used to help diagnose diseases associated with the liver, disorders that block bile ducts and bone disorders. Because this test is not specific for liver or bone, other liver- or bone-specific blood tests are usually needed to help determine the source of an increased blood alkaline phosphatase level. Symptoms may also help determine the source. Otherwise, an alkaline phosphatase isoenzyme test can determine the source.

Normal Values

The normal value for alkaline phosphatase is 53 to 128 U/L for a 20- to 50-year-old man and 42 to 98 U/L for a 20- to 50-year-old woman. Pregnant women typically have higher alkaline phosphatase values due to contributions from the placenta. Normal values are slightly different if you are older than 60 -- 56 to 119 U/L if you're a man or 53 to 141 U/L if you're a woman.

Normal values can vary slightly among testing laboratories. Normal values from the laboratory performing the test should be used when interpreting the test results.

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  • Tietz Textbook of Clinical Chemistry and Molecular Diagnostics, Fourth Edition; Carl Burtis, et al.
  • Differential Diagnosis in Primary Care; R. Douglas Collins, M.D.
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