ALP - blood test

Alkaline phosphatase

Blood test

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Definition

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

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 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

This test may be done:

  • To diagnose liver or bone disease
  • To check if treatments for those diseases are working
  • To check for side effects from medicines

Normal Results

The normal range is 40 to 129 international units per liter (IU/L) or 0.68 to 2.19 microkatal per liter (µkat/L).

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

Lower-than-normal ALP levels

Other conditions for which the test may be done:

References

Fogel EL, Sherman S. Diseases of the gallbladder and bile ducts. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 141.

Korenblat KM. Approach to the patient with jaundice or abnormal liver tests. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 133.

Martin P. Approach to the patient with liver disease. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 132.

Pincus MR, Abraham NZ, Bluth M. Interpreting laboratory results. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 9.

GO

Review Date: 5/19/2025

Reviewed By: Jacob Berman, MD, MPH, Clinical Assistant Professor of Medicine, Division of General Internal Medicine, University of Washington School of Medicine, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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