Alkaline phosphatase (ALP) is a protein found in all body tissues. Tissues with higher amounts of ALP include the liver, bile ducts, and bone.
A blood test can be done to measure the level of ALP.
A related test is the ALP isoenzyme test.
How the Test is Performed
A blood sample is needed. Most of the time blood is typically drawn from a vein located on the inside of the elbow or the back of the hand.
How to Prepare for the Test
You should not to eat or drink anything for 6 hours before the test, unless otherwise instructed by your doctor.
Many medicines can interfere with blood test results.
- Your health care provider will tell you if you need to stop taking any medicines before you have this test.
- Do not stop or change your medications without talking to your doctor first.
How the Test Will Feel
You may feel slight pain or a sting when the needle is inserted. You may also feel some throbbing at the site after the blood is drawn.
Why the Test is Performed
Reasons the test may be done include:
- To diagnose liver or bone disease.
- To check, if treatments for those diseases are working.
- As part of a routine liver function test.
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. High levels of ALP are normally seen in children undergoing growth spurts and in pregnant women.
The examples above show the common measurements for results for these tests. Some laboratories use different measurements or may test different specimens.
What Abnormal Results Mean
Abnormal results may be due to the following conditions:
Higher-than-normal ALP levels
- Biliary obstruction
- Bone conditions
- Osteoblastic bone tumors, osteomalacia, a fracture that is healing
- Liver disease or hepatitis
- Eating a fatty meal if you have blood type O or B
- Paget's disease
Lower-than-normal ALP levels
- Protein deficiency
- Wilson's disease
Other conditions for which the test may be done:
Afdhal NH. Diseases of the gall bladder and bile ducts. In: Goldman L, Schafer AI, eds.Cecil Medicine
Berk P, Korenblat K. Approach to the patient with jaundice or abnormal liver tests. In: Goldman L, Schafer AI, eds.Cecil Medicine
Martin P. Approach to the patient with liver disease. In: Goldman L, Schafer AI, eds.Cecil Medicine
- Alcoholic liver disease
- Alcohol use disorder
- Bile duct obstruction
- Biliary stricture
- Bone tumor
- Broken bone
- Liver disease
- Multiple endocrine neoplasia (MEN) II
- Paget’s disease of the bone
- Protein in diet
- Renal cell carcinoma
- Temporal arteritis
Update Date 4/29/2013
Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, Bethanne Black, Stephanie Slon, and Nissi Wang.