Alkaline Phosphatase (ALP)

What do the results of an alkaline phosphatase (ALP) blood test mean?

Blood test reports, including alkaline phosphatase (ALP) test reports, usually provide the following information:

• The name of the blood test or what was measured in your blood.
• The number or measurement of your blood test result.
• The normal measurement range for that test.
• Information that indicates if your result is normal or abnormal or high or low.

What is the normal range for alkaline phosphatase (ALP)?

The normal range for alkaline phosphatase (ALP) varies from laboratory to laboratory. One common reference range is from 44 to 147 international units per liter (IU/L), but some organizations recommend a range of 30 to 120 IU/L. Because of this, it’s important to check your test result report to see what your specific lab’s reference range is.

It’s also important to note that normal alkaline phosphatase levels vary with age and sex. ALP levels are typically elevated during childhood and puberty due to bone growth and development. Between the ages of 15 to 50 years, ALP levels are slightly higher in males than females. ALP levels then rise again in old age.

ALP levels may also be higher if you’re pregnant since ALP exists in the placenta and in people who are healing from a bone fracture (break).

What does it mean if my alkaline phosphatase (ALP) is high?

It’s important to note that elevated levels of ALP can range in severity. While a very high ALP level often means you have liver damage or a bone disorder, mildly elevated levels can be caused by many different factors — not necessarily a medical condition that needs treatment. If you only have a mild elevation in your ALP levels, your healthcare provider will likely not have you undergo extensive evaluation. Instead, they’ll likely monitor your levels over time to make sure they don’t get worse.

High alkaline phosphatase (ALP) levels may indicate that there’s damage to your liver or that you have a type of bone disorder. Liver damage creates a different type of ALP than bone disorders do. If your test results reveal that you have high ALP levels, your provider may have you undergo additional tests, such as an ALP isoenzyme test, to determine where the excess ALP is coming from.

High alkaline phosphatase levels in the liver may indicate the following conditions:

• Cholestasis of pregnancy: This is a common liver disease that can develop late in pregnancy.
• Cirrhosis of the liver: Cirrhosis is a late-stage liver disease in which healthy liver tissue is replaced with scar tissue and the liver is permanently damaged.
• Hepatitis: Hepatitis is inflammation of the liver. There are many types of hepatitis.
• Biliary atresia: This is a rare condition that happens when there’s a blockage in the tubes (ducts) that carry bile from your liver to your gallbladder. It occurs in infants.
• Biliary stricture: This condition happens when the bile duct (the tube that takes bile from the liver to the small bowel) gets smaller or narrower.
• Biliary obstruction due to cancer: Certain cancers, including cholangiocarcinoma and pancreatic head adenocarcinoma, can block your bile ducts or pancreatic ducts.
• Mononucleosis (“mono”): This is a contagious infection that can sometimes cause swelling in your liver.

High bone alkaline phosphatase levels may indicate the following conditions:

• Bone metastasis: This condition happens when cancer cells from elsewhere in your body spread to your bones.
• Paget’s disease of the bone (osteitis derformans): This is a rare chronic bone disorder in which there is excessive breakdown and regrowth in the affected bone(s).
• Osteogenic sarcoma: This is a type of cancer that starts in your bones.
• Healing fractures.
• Hyperparathyroidism: This condition happens when your parathyroid glands release too much parathyroid hormone, which causes calcium levels in your blood to rise.
• Hyperthyroidism: This condition happens when your thyroid produces and releases too much thyroid hormone.
• Osteomalacia: This is a disease that weakens your bones and can cause them to break more easily. It develops most commonly due to a vitamin D deficiency.

A high level of ALP may also be a sign of untreated celiac disease.

What does it mean if my alkaline phosphatase (ALP) is low?

Having an abnormally low level of alkaline phosphatase (ALP) is less common than having an elevated level. It may indicate the following conditions:

• Malnutrition.
• Zinc deficiency.
• Magnesium deficiency.
• Hypothyroidism.
• Rare genetic conditions, including hypophosphatasia and Wilson disease.

Should I be concerned if I have high or low alkaline phosphatase (ALP) test results?

If your ALP test result is high or low, it doesn’t necessarily mean that you have a medical condition that needs treatment. Other factors can affect your levels, including:

• Certain medications, such as birth control pills.
• Your diet.
• Being pregnant.
• Your age — teens and children may have higher levels because their bones are growing.
• Having AIDS.
• An error in the collection, transport or processing of the test.

Before determining if you need to undergo further tests, your healthcare provider will take into consideration many aspects of your health and situation, including:

• Your medical history.
• Your current medications.
• How high or low your ALP results are.
• The results of other tests usually taken alongside ALP.
• If you’re experiencing symptoms.

When should I call my doctor?

If you’re experiencing symptoms of liver damage, such as jaundice, or bone disorders, such as bone or joint pain, call your healthcare provider. If you’ve been diagnosed with a liver condition or a bone disorder and are experiencing new or concerning symptoms, contact your provider.

If you have any questions about you’re alkaline phosphatase results, don’t be afraid to ask your provider questions.