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Alkaline phosphatase (ALP) is an enzyme that is involved in a wide range of processes and is found in many parts of the body, particularly the liver and bones with smaller amounts in the intestines. Each of these body parts makes different forms of ALP.
ALP is typically measured as part of Liver Function Tests (LFTs). This is a standard group of tests that is routinely used to check the health of the liver.
LFTs measure enzymes and proteins that are either produced by the liver cells as part of its normal function or released into the blood when liver cells are damaged. Looked at together, along with your symptoms and medical history, they help build a picture of your liver’s health. Either higher or lower than normal levels of these substances can indicate a problem with your liver.
As well as ALP, they measure the enzymes gamma-glutamyl transferase (GGT), alanine transaminase (ALT) and aspartate aminotransferase (AST), together with bilirubin (a breakdown product from red blood cells that is removed from the body by the liver) and albumin (the most common protein in your blood which is made by your liver).
ALP levels are affected by a wide range of health conditions including liver disease, conditions that affect bone growth, infections, bile duct blockages and gastrointestinal disorders (issues with your gut).
Any condition that affects bone growth or causes increased activity of bone cells can affect ALP blood levels. Measuring ALP is used to help diagnose bone disease such as low vitamin D levels, Paget’s disease (a condition that causes malformed bones) or cancers that have spread to the bones. If you are recovering from a bone injury you may have a raised ALP level while their bone heals. Children have higher levels of ALP than adults because their bones are growing.
Sample
Blood.
Any preparation?
None.
Reading your test report
Your results will be presented along with those of your other tests on the same form. You will see separate columns or lines for each of these tests.
| Condition | Possible ALP results |
| Liver damage or bone disease | If the levels of other liver enzymes and proteins measured in the LFTs panel are also raised, this usually indicates that you have a liver problem. If other LFT levels are normal, this suggests that the ALP is coming from your bones. Your doctors will need to investigate further. If it is not clear if ALP is raised due to liver disease or bone disease, your doctors may order a test such as ALP isoenzymes to help work this out. |
| Hepatitis | In some forms of liver disease such as hepatitis, ALP is usually much less elevated than AST or ALT. |
| Bile duct blockages | The test is often used to detect blocked bile ducts because ALP is especially high in the cells that line the bile ducts of the liver. If one or more of them are obstructed, for example by gallstones or a tumour, then blood levels of ALP will often be high. When the bile ducts are blocked (for example through scarring, gallstones, previous surgery or by a tumour), ALP may be increased much more than either AST or ALT. The GGT and the bilirubin may also be raised. |
| Gastrointestinal disorders | ALP can be elevated in some gastrointestinal (gut) diseases like coeliac disease, inflammatory bowel disease (IBD) and intestinal infections. |
| Pregnancy | ALP levels naturally rise during pregnancy, particularly in the third trimester, due to increased production from the placenta. Extremely high levels of ALP may indicate intrahepatic cholestasis of pregnancy (ICP). This is a build-up of bile in the liver during pregnancy. Low ALP levels in pregnancy may indicate intrauterine growth restriction (IUGR) – a condition where the foetus is not growing as big as it should. |
Reference intervals
Your results will be compared to reference intervals (sometimes called a normal range).
If your results are flagged as high or low this does not necessarily mean that anything is wrong. It depends on your personal situation. Your results need to be interpreted by your doctor.
ALP Reference Intervals Many factors affect ALP levels including age, blood type and gender. Hence, there are age and gender specific reference intervals. | |
| Adult (male and female) | 30 - 110 U/L |
| Infants, adolescents and young adults | This group have higher levels of ALP than adults because their bones are growing. The appropriate reference intervals will be provided on the pathology report. |
| The reference intervals for this test are common reference intervals which means that all laboratories in Australia should be using this same target range. | |
The choice of tests your doctor makes will be based on your medical history and symptoms. It is important that you tell them everything you think might help.
You play a central role in making sure your test results are accurate. Do everything you can to make sure the information you provide is correct and follow instructions closely.
Talk to your doctor about any medications you are taking. Find out if you need to fast or stop any particular foods or supplements. These may affect your results. Ask:
Pathology and diagnostic imaging reports can be added to your My Health Record. You and your healthcare provider can now access your results whenever and wherever needed.
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