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Alkaline Phosphatase

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

  • Taking medicines that may damage the liver, such as some antibiotics, birth control pills, long-term aspirin use, and oral diabetes medicines.
  • Going through menopause. Postmenopausal women may have higher ALP levels than women who still have menstrual cycles.
  • Your age. Children normally have much higher ALP levels than adults because rapid bone growth is normal in children and bones make ALP.
  • Drinking a lot of alcohol.

What To Think About

  • If the ALP level is high, other tests may be done to determine whether a liver or bone problem is present.
  • If liver disease is suspected, more blood tests, an ultrasound, or a CT scan are generally recommended to find the problem.
  • Other tests to check liver function, such as alanine aminotransferase, aspartate aminotransferase, and bilirubin, are often done at the same time as an alkaline phosphatase (ALP) test.
  • Gamma glutamyl transferase (GGT), or gamma glutamyl transpeptidase, may be measured in the blood to check the difference between bone ALP and liver ALP. High levels of GGT are present when the liver is damaged but not present with bone disease. A high level of GGT may be caused by alcohol use or may mean that blocked bile ducts are causing inflammation. The level of GGT may be high with the use of certain medicines, such as phenytoin and phenobarbital. In some medical centers, a test that measures a substance called 5-nucleotidase is done instead of the GGT test because it is better at finding liver disease.


  1. Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.

Other Works Consulted

  • Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.

  • Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.

  • Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.

WebMD Medical Reference from Healthwise

Last Updated: November 14, 2014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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