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 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 your health care provider tells you otherwise.
Many medicines can interfere with blood test results.
- Your provider will tell you if you need to stop taking any medicines before you have this test.
- DO NOT stop or change your medicines without talking to your provider 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) or 0.73 to 2.45 microkat/L.
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 disease
Lower-than-normal ALP levels
- Protein deficiency
- Wilson disease
Other conditions for which the test may be done:
Berk P, Korenblat K. Approach to the patient with jaundice or abnormal liver tests. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 147.
Fogel EL, Sherman S, eds. Diseases of the gallbladder and bile ducts. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 155.
Martin P. Approach to the patient with liver disease. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 146.
Review Date 4/30/2015
Updated by: Laura J. Martin, MD, MPH, ABIM Board Certified in Internal Medicine and Hospice and Palliative Medicine, Atlanta, GA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.