Alkaline Phosphatase (ALP) Level Test: Reference Range

An alkaline phosphatase (ALP) level test measures the amount of alkaline phosphatase enzyme in your bloodstream. Enzymes are proteins that help chemical reactions happen. For instance, they can break big molecules down into smaller parts, or they can help smaller molecules join to form bigger structures.

The alkaline phosphatase test is usually performed to diagnose conditions associated with the hepatobiliary system (the liver, bile ducts and the gallbladder) or bone disease. Diseases that destroy the cells of organs containing alkaline phosphatase lead to the release of ALP into the blood, which raises the blood level of alkaline phosphatase.

Reference Range

The normal range of ALP varies from person to person and depends on your age, blood type, gender, and whether you’re pregnant.

The normal range for serum ALP level is 20 to 140 IU/L, but this can vary from laboratory to laboratory. The normal range runs higher in children and decreases with age.

Higher-than-normal levels of ALP in your blood may indicate a problem with your liver or gallbladder. This could include hepatitis, cirrhosis, liver cancer, gallstones, or a blockage in your bile ducts.

High levels may also indicate an issue related to the bones such as rickets, Paget’s disease, bone cancer, or an overactive parathyroid gland. In rare cases, high ALP levels can indicate heart failure, kidney cancer, other cancer, mononucleosis, or bacterial infection.

If your ALP level is high, your doctor may have you take another test, called an ALP isoenzyme test, to determine whether the alkaline phosphatase in your blood is coming from your liver or your bones.

Having lower-than-normal ALP levels in your blood is rare, but it can indicate malnutrition, which could be caused by celiac disease or a deficiency in certain vitamins and minerals.

The best way to know what is normal or not is to discuss the results with your doctor, who will be able to interpret the lab’s specific result and reference ranges.


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* The Content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.