Test Quick Guide

Alkaline phosphatase (ALP) is an enzyme present in many parts of the body, but it is primarily found in the liver, bones, intestine, and kidneys.

ALP testing measures the amount of this enzyme in the blood. Abnormal levels of ALP can be caused by liver or bone conditions and other types of health problems.

ALP can be tested alone, but because many conditions can affect ALP levels, it is common to test it alongside other enzymes, such as in a liver panel test, to obtain more information about the most likely cause of abnormal results. An ALP isoenzyme test can identify the part of the body where ALP in the blood originated, but this testing is complex and not widely available.

About the Test

Purpose of the test

The purpose of testing ALP is to determine if you have normal levels of this enzyme. An ALP blood test can be used for screening, diagnosis, and monitoring of liver or bone diseases and other health conditions.

Screening is checking for health problems before any symptoms have occurred. This rarely measures ALP alone, but it is a standard part of multi-measurement tests such as a liver panel and comprehensive metabolic panel (CMP). These tests may be prescribed as part of a routine checkup to screen for a range of potential health problems.

Diagnosis is the process of finding the cause after symptoms have developed. ALP is most often tested for diagnosis when there are signs of possible liver problems, such as nausea and vomiting, jaundice, fatigue, abdominal pain, or unexplained weight loss.

It is also often prescribed if you have symptoms of a possible bone disorder, such as bone pain, susceptibility to bone fractures, or abnormal bone shape. ALP measurement as part of a liver panel or CMP may help identify the cause of general symptoms.

While ALP levels alone are insufficient to diagnose an underlying condition, they can be an important part of the diagnostic process. The degree of ALP elevation may reflect the type or severity of a condition. An ALP isoenzyme test to measure specific kinds of ALP can help determine the part of the body affected and assist in diagnosing the problem.

Monitoring is tracking the course of a health condition or your response to treatment. An ALP test, often as part of a panel, may be used to see if liver disease or other conditions are improving, worsening, or staying the same.

What does the test measure?

This test measures ALP, which is a type of enzyme. The typical measurement for this test is international units per liter (IU/L), a standardized measurement utilized by most laboratories based on the biological activity of ALP.

ALP’s exact function in the body is not fully understood, but researchers believe it to be important to multiple processes. The enzyme can be found in the liver, bones, placenta of pregnant women, intestine, kidneys, and other body parts. Abnormal levels in the blood can reflect damage to tissue or disruption of normal processes in the body.

Another type of ALP testing is an ALP isoenzyme or ALP fractionation test. In this test, specific subtypes of ALP are measured. These subtypes indicate where in the body the ALP was produced. While this testing can be beneficial, it is technically challenging and much less common than general ALP testing.

When should I get this test?

When ALP is tested, it is most often part of a panel test that includes other measurements that can reflect liver and kidney health. For example, the liver panel and CMP may measure ALP as part of a routine checkup or if you have symptoms that could be caused by liver or kidney conditions.

Testing for ALP alone may be conducted when you have symptoms of a problem affecting your liver or bones. It may also help monitor your response to treatment for liver or bone diseases.

ALP isoenzyme tests are most common as a follow-up after finding abnormal levels of ALP on a prior test.

Because testing for ALP can be used in many different medical contexts, a physician can best determine when it should be prescribed.

Finding an Alkaline Phosphatase Test

How can I get an alkaline phosphatase test

ALP tests are normally prescribed by a doctor. They may recommend a blood test for ALP alone, but in most cases, ALP will be included among several measurements on a panel test. Testing requires a blood draw typically done in a medical office, hospital, or laboratory.

Can I take the test at home?

At-home ALP testing is not widespread, but some at-home options are available to measure it as part of a liver panel. In these tests, you take a blood sample with a fingerstick and then send it to a laboratory to analyze it.

ALP isoenzyme tests are generally not available with at-home test kits.

How much does the test cost?

The price for ALP testing can vary based on where you live, where your blood sample is taken, whether ALP is tested alone or with other measurements, and whether you have health insurance. Costs for ALP isoenzyme testing may be different from costs for standard ALP tests.

Technician fees for the blood draw, laboratory fees, and charges for office visits can all be included in the cost of an ALP test. Health insurance often covers most or all of these costs when your doctor prescribes the test, but you may need to pay a deductible or copay.

At-home tests are not covered by insurance and may be available for less than $150.

For details about your out-of-pocket costs for ALP tests, check directly with your doctor’s office and your health insurance provider.

Taking an Alkaline Phosphatase Test

ALP tests, including ALP isoenzyme tests, are usually done with a blood sample taken from a vein in your arm. The blood sample can be taken in a health clinic, medical office, laboratory, or a similar setting.

You can obtain a sample with a fingerstick for an at-home test and then send that by mail to a medical lab.

Before the test

Test preparations can depend on the specifics of the test being performed and the requirements of the laboratory that will analyze your sample:

  • ALP tests alone don’t always require fasting, but some laboratories may request that you not eat any food or drink anything other than water for six to 12 hours before the test.
  • When ALP is tested as part of a panel, it is common for fasting to be required.
  • ALP isoenzyme tests also usually require fasting.

You may also be asked about any medications or supplements you take, and your doctor will advise you if you need to adjust the timing or dosage of these before the test.

For at-home tests, carefully consult any instructions provided by the test kit to find out if any special preparations are required.

During the test

For standard ALP tests, a sample of blood will be drawn from your arm. An elastic band will be placed around your upper arm to increase blood flow through your veins. A technician will use an antiseptic wipe on the underside of your arm near the elbow and will insert a needle into the vein to withdraw a small vial of blood.

The blood draw is usually complete within a couple of minutes. There may be a brief sting when the needle is inserted and removed.

Materials and instructions will be included in the kit for an at-home test. You will need to clean your fingertip with an antiseptic and then prick it with a small needle to obtain a drop of blood applied to the provided test paper. That test paper must be prepared to be sent by mail to the lab. Follow any instructions to ensure proper at-home sample collection.

After the test

After your blood draw is finished, a cotton swab or bandage will apply pressure and stop any continued bleeding. Serious effects are uncommon, but there may be tenderness in your arm. Some bruising around the puncture site is also possible.

You can return to driving and most normal activities once the test is complete. If you were required to fast, you may want to bring something to eat after the test.

You usually will not have lasting pain or bleeding for an at-home test, but a bandage can be applied if your fingertip keeps bleeding.

Alkaline Phosphatase Test Results

Receiving test results

ALP test results are normally available within a few business days after the lab receives your sample. Your test report may be sent in the mail or electronically, and your doctor’s office may also contact you to share your test results.

Receiving results may take a few extra days for at-home tests because your test sample has to be sent by mail to the laboratory. The test report is normally accessible online or with a smartphone app, although you may also be contacted by a health professional that works for the at-home testing company.

Interpreting test results

Your test report will show your measured ALP level, usually reported in international units per liter (IU/L). The report may also list a reference range, which can vary from laboratory to laboratory. One common reference range is from 44 to 147 IU/L, but some professional organizations recommend a range of 30-120 IU/L. For this reason, it’s important to check your test report for the lab’s reference range that analyzed your sample.

Elevated ALP can be indicative of liver or bone diseases as well as many other types of conditions. But high ALP levels are not always a sign of a problem. Interpretation of your test results can involve consideration of multiple factors:

  • The degree of elevation: Very high levels are often seen with blockages of the bile ducts, but these levels alone cannot distinguish between liver problems and other conditions.
  • Other test measurements: ALP is often measured along with other enzymes, such as aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma-glutamyl transpeptidase (GGT), and/or 5′-nucleotidase (5’-NT), and the levels of ALP relative to these enzymes can help determine the significance of your test result.
  • Your overall health: Any symptoms you are experiencing will be considered alongside your ALP levels.

Your doctor can account for the fact that ALP levels can be elevated without any underlying illness. For example, ALP is usually higher in pregnant women, growing children and adolescents, and older adults. ALP produced in the intestine can also increase after fatty meals for people with certain blood types.

Abnormally low ALP levels are less common but can occur due to malnutrition, nutrient deficiencies, hypothyroidism, and some rare inherited disorders that affect ALP or liver function. Persistently low levels of ALP could indicate hypophosphatasia (HPP), a rare genetic disorder of bone metabolism.

If you have ALP isoenzyme testing, your test report will show levels for different types of ALP. Elevations of specific sources of ALP can identify the location of tissue damage or another disease in the body.

Regardless of the type of ALP test that you take, it is important to discuss your test results with your doctor, who can best explain what they mean for your health and whether any other testing would be beneficial.

As you discuss your test report with your doctor, these questions may help you better understand your situation and the most appropriate next steps in your care:

  • What did the test show about my ALP levels?
  • Were any other measurements taken in addition to ALP? What can you learn from those measurements?
  • Do you recommend any other tests? What are the pros and cons of different follow-up tests?

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