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Alkaline Phosphatase

What is an Alkaline Phosphatase Test?

An alkaline phosphatase (ALP) test measures the amount of ALP in your blood. ALP is an enzyme found in many parts of your body. Each part of your body produces a different type of ALP. Most ALP is found in your liver, bones, kidneys, and digestive system.

Abnormal levels of ALP in your blood may be a sign of a wide range of health conditions, including liver disease, bone disorders, and chronic kidney disease. But an alkaline phosphatase test alone can't identify the source of ALP in your blood, so other tests are usually needed to make a diagnosis.

Other names: ALP, ALK, PHOS, Alkp, ALK PHOS

What is it used for?

An alkaline phosphatase test is often used to screen for or help diagnose diseases of the liver or bones. The test may also help diagnose or monitor other health conditions.

Why do I need an alkaline phosphatase test?

Your health care provider may order an alkaline phosphatase test as part of a routine checkup. Many conditions may affect ALP levels, so the test is often done with other blood tests. These other tests include a comprehensive metabolic panel (CMP) or liver function tests that check how well your liver is working.

An alkaline phosphatase test may also be ordered if you have symptoms of liver damage or a bone disorder. Symptoms of liver disease include:

Symptoms of bone disorders include:

  • Pain in your bones
  • Inflammation and arthritis in your joints
  • Bones that are unusually shaped and/or too large
  • Broken bones

What happens during an alkaline phosphatase test?

An alkaline phosphatase test is a type of blood test. During the test, a health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

Will I need to do anything to prepare for the test?

Preparations for an alkaline phosphatase test depend on the lab doing the test. Some labs require you to fast (not eat or drink) for 6 to 12 hours before the test. Also, the ALP test is usually ordered with other blood tests. You usually need to fast for several hours before these tests. Your provider will let you know if there are any special instructions to follow.

Are there any risks to the test?

There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

What do the results mean?

High alkaline phosphatase (ALP) levels may be a sign of a liver problem or a bone disorder. Liver problems and bone disorders cause different types of ALP. But your test results can't tell which type of ALP is high.

If your test results show high ALP levels, your provider may order other tests to help figure out what's causing the problem. These tests may include:

  • An ALP isoenzyme test. This test can tell which part of your body is making the ALP. But this test may not available everywhere.
  • Liver function tests. If the results of these tests are also high, then your high ALP level is likely from a problem in your liver.

High alkaline phosphatase levels from your liver may be a sign of:

If alkaline phosphatase levels are high and the results of liver tests are normal, the problem may be a bone disorder, such as Paget's disease of bone. This disease makes your bones unusually large and weak, causing them to break more easily.

Moderately high levels of ALP may be a sign of a many different types of conditions, including Hodgkin lymphoma, heart failure, or certain infections.

It's possible to have higher than normal levels of ALP and not have a medical condition that needs treatment. Your provider will consider your symptoms, medical history, and other test results to make a diagnosis.

Low levels of ALP are less common. They may be a sign of a lack of zinc, malnutrition, pernicious anemia, thyroid disease, Wilson disease or hypophosphatasia, a rare genetic disease that affects bones and teeth.

Learn more about laboratory tests, reference ranges, and understanding results.

Is there anything else I need to know about alkaline phosphatase test?

Many things can affect ALP levels. Pregnancy can cause higher than normal ALP levels. Children and teens may have high levels of ALP because their bones are growing. Birth control pills and certain medicines may lower ALP levels, while other medicines can cause the levels to increase. Even eating a fatty meal before an alkaline phosphatase test may also cause a small increase in ALP.

To learn what your results mean, talk with your provider.


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The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.