Also Known As
Alk. Phos.
Formal Name
Alkaline Phosphatase
This article was last reviewed on
This article waslast modified on 21 October 2020.
At a Glance
Why Get Tested?

To screen for or monitor treatment for a liver or bone disorder

When To Get Tested?

As part of liver function tests, bone profile tests or when a person has symptoms of a liver or bone disorder

Sample Required?

A blood sample is taken by needle from a vein in the arm

Test Preparation Needed?

Fasting is preferred but not essential for this test. Eating a meal can increase the ALP level slightly for a few hours in some people. It is usually better to do the test after fasting overnight. In this case, only water is permitted.

On average it takes 7 working days for the blood test results to come back from the hospital, depending on the exact tests requested. Some specialist test results may take longer, if samples have to be sent to a reference (specialist) laboratory. The X-ray & scan results may take longer. If you are registered to use the online services of your local practice, you may be able to access your results online. Your GP practice will be able to provide specific details.

If the doctor wants to see you about the result(s), you will be offered an appointment. If you are concerned about your test results, you will need to arrange an appointment with your doctor so that all relevant information including age, ethnicity, health history, signs and symptoms, laboratory and other procedures (radiology, endoscopy, etc.), can be considered.

Lab Tests Online-UK is an educational website designed to provide patients and carers with information on laboratory tests used in medical care. We are not a laboratory and are unable to comment on an individual's health and treatment.

Reference ranges are dependent on many factors, including patient age, sex, sample population, and test method, and numeric test results can have different meanings in different laboratories.

For these reasons, you will not find reference ranges for the majority of tests described on this web site. The lab report containing your test results should include the relevant reference range for your test(s). Please consult your doctor or the laboratory that performed the test(s) to obtain the reference range if you do not have the lab report.

For more information on reference ranges, please read Reference Ranges and What They Mean.

What is being tested?

Alkaline phosphatase is an enzyme found in high amounts in bone and liver. Smaller amounts of ALP are found in the placenta of women who are pregnant, and in the intestines. Each of these body parts makes different forms of ALP. The different forms are called isoenzymes.

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Common Questions
  • How is it used?

    When a person has evidence of liver disease, very high ALP levels can tell the doctor that the person’s bile ducts are somehow partially or totally blocked or inflamed. Often, ALP is high in people who have cancer that has spread to the liver or the bones, and doctors can do further testing to see if this has happened. If a person with bone or liver cancer responds to treatment, ALP levels will usually decrease. When a person has high levels of ALP, and the doctor is unsure why, ALP isoenzymes might be requested to try to determine the cause.

  • When is it requested?

    ALP is generally part of a routine laboratory test profiles called liver function tests or bone profile. It is usually requested with several other tests if a patient has symptoms of a liver or bone disorder.

  • What does the test result mean?

    Raised levels of ALP are usually due to a disorder of either the bone or liver. If other liver function tests such as bilirubin, gamma-glutamyl transferase (GGT) or alanine aminotransferase (ALT) are also raised, this usually indicates that the ALP is coming from the liver. However if calcium and phosphate measurements are abnormal, this suggests that the ALP might be coming from bone. In some forms of liver disease, such as hepatitis, ALP is usually much less elevated than AST or ALT. However, when the bile ducts are blocked (for example by gallstones, scars from previous gallstones or surgery, or by a tumour), ALP and bilirubin may be increased much more than either AST or ALT.
    ALP can also be raised in bone diseases such as Paget’s disease (where bones become enlarged and deformed), osteomalacia, in certain cancers that spread to bone or in vitamin D deficiency.

  • Is there anything else I should know?

    Pregnancy can increase ALP levels. Children have higher ALP levels because their bones are growing, and ALP is often very high during 'growth spurts' that occurs at different ages in males and females. Temporary elevations of ALP are also seen with healing fractures. Transient benign increases in ALP may also be seen in young infants.

    Eating a meal can increase the ALP level slightly for a few hours in some people. Ideally the test should be done after fasting overnight. Some drugs may increase ALP levels, especially antibiotics, antihistamines and some of the drugs used to treat psychiatric problems or epilepsy but significant increases are rare.

  • What other tests are used to evaluate liver disorders?

    Other commonly used liver tests include other enzymes found in liver cells, such as alanine aminotransferase (ALT) , GGT, aspartate aminotransferase (AST), and bilirubin (a breakdown product derived from the haemoglobin in red blood cells removed from the body by the liver).

  • Who is at risk for a liver disorder?

    While many things could harm the liver, the major causes of liver disease are infection by viruses and the drinking of too much alcohol. In rare cases, some medicines can damage the liver; your doctor may suggest liver tests from time to time if you are taking any of these drugs. Some diseases inherited from your parents can also occasionally damage the liver.

  • What signs should make me aware of a liver disorder?

    In many cases, liver disease has few symptoms. When the liver is damaged rapidly (a disease called acute hepatitis), the skin and the whites of the eyes often turn yellow, the urine turns brown, and bowel movements lose their colour. In its late stages, liver disease may cause confusion, easy bruising, swelling in your abdomen, and the vomiting of blood.