MedlinePlus Medical Encyclopedia: ALP

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ALP

Contents of this page:
Alternative names Definition How the test is performed How to prepare for the test	Why the test is performed Normal Values What abnormal results mean Special considerations

Alternative names

Alkaline phosphatase

Definition Return to top

This is a blood test that measures the amount of the enzyme ALP (alkaline phosphatase).

How the test is performed Return to top

Blood is drawn from a vein or from a capillary on the heel, finger, toe, or earlobe. The laboratory centrifuges the blood to separate the serum from the cells. The ALP test is done on the serum.

How to prepare for the test Return to top

Fast for 6 hours.

Your health care provider may advise you to discontinue drugs that may affect the test, such as:

antibiotics
narcotics
methyldopa
propranolol
cortisone
allopurinol
tricyclic antidepressants
chlorpromazine
oral contraceptives (birth control pills)
anti-inflammatory analgesics
androgens
tranquilizers
some antiarthritic drugs
oral antidiabetic drugs.

Why the test is performed Return to top

Alkaline phosphatase is an enzyme found in all tissues. Tissues with particularly high concentrations of ALP include the liver, bile ducts, placenta, and bone.

Damaged or diseased tissue releases enzymes into the blood, so serum ALP measurements can be abnormal in many conditions, including bone disease and liver disease. Serum ALP is also increased in some normal circumstances (for example, during normal bone growth) or in response to a variety of drugs.

There are multiple varieties of ALP, called isoenzymes. Different types of isoenzymes, each with different structures, are found in different tissues (for example, liver and bone ALP isoenzymes have different structures) and can be quantified separately in the laboratory. To differentiate the location of damaged or diseased tissue in the body, ALP isoenzyme testing must be done.

Normal Values Return to top

The normal range is 44 to 147 IU/L (international units per liter).

Normal values may vary slightly from laboratory to laboratory. They also can vary with age and gender.

What abnormal results mean Return to top

Higher-than-normal ALP levels may indicate:

Lower-than-normal ALP levels (hypophosphatasemia) may indicate:

malnutrition
protein deficiency

Additional conditions under which the test may be performed:

Special considerations Return to top

The ALP levels vary with age and gender. It is normal for young children experiencing rapid growth and for pregnant women to have high levels of ALP.

Update Date: 8/18/2003

Updated by: David Webner, M.D., Sports Medicine Fellow, Crozer-Keystone Family Practice Program, Springfield, PA. Review provided by VeriMed Healthcare Network.

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