Your doctor may measure levels of alkaline phosphatase in your blood if you are suspected of having a liver or bone disorder. Specific reference ranges for normal, low or high levels vary depending on test specifics and demographics. High levels indicate liver damage or increase bone growth. Low levels are uncommon and are seen after blood transfusion and in certain rare conditions.
About Alkaline Phosphatase
Alkaline phosphatase is an enzyme that removes phosphate groups that have been linked to proteins or molecules as a signal or to alter their activity. ALP functions most efficiently in body tissues that are alkaline or basic. Although ALP is produce by all tissues in your body, cells of the liver, bile ducts and osteoblasts or cells that promote the formation of bone produce the highest amounts. ALP is measured as a non-invasive test of bone growth or liver health. The particular reference ranges for your ALP test depend on your age, ethnicity and methods of the lab and will be noted on your test results.
High Levels
Levels of ALP that are considered high indicate that you may have liver damage, a condition increasing bone growth or blockage of the bile ducts. Other tests to assess liver and bone function may be performed at the same time to indicate whether high ALP is due to a liver or bone condition. Further tests can also be conducted to determine whether ALP originated from bone or liver cells.
Low Levels
Low levels of ALP are not commonly detected. ALP may be artificially low after blood transfusion or cardiovascular surgery. Malnutrition or a dietary deficiency of protein or zinc can also cause ALP levels to be low. There are also rare genetic disorders of bone metabolism that can cause low ALP levels, although ALP is not commonly used a diagnostic criteria for these diseases.
Factors that May Alter Results
Many medicines may inhibit or increase levels of ALP in your body tissues. These medicines include antibiotics, anti-inflammatory drugs, hormones including male and female hormone replacement and birth control and some antidepressants. Your doctor may request that you temporarily discontinue these drugs prior to an ALP test. Consumption of alcohol or drugs may also bias ALP test results.
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