Everything You Need To Know About the ALP Blood Test

Determining the level of ALP or alkaline phosphatase in your blood exposes underlying health issues that require proper attention. ALP in blood tests is mainly associated with aiding the assessment of liver and bone health. However, this enzyme also plays a role in other bodily processes, including intestinal function and even placental development during pregnancy. Read on to learn more about what the ALP blood test is all about.

Did You Know? You can order an ALP blood test online. Take it as a standalone test or as a part of metabolic blood tests, such as that of the comprehensive metabolic panel (CMP). Within minutes, you can book your appointment with an accredited laboratory of your choice. 

What is Alkaline Phosphatase or ALP?

The enzyme alkaline phosphatase (ALP)⁽¹⁾ is found throughout the body, with particularly high levels in the liver, bones, and intestines. As an enzyme, it catalyzes the breakdown and removal of phosphate groups in molecules. 

However, its specific functions vary depending on its location in the body, but it is generally associated with bone mineralization, cell signaling, and nutrient absorption. Measuring ALP levels in the blood can be a valuable diagnostic tool, as abnormal levels may indicate liver disease⁽²⁾, bone disorders⁽³⁾, or other health conditions.

Medical laboratories may have varying reference ranges for normal ALP levels. Hence, make sure to check it in your test results. For a more general guide, see the following values. 

• Adults: The normal range for adults usually falls between 44 and 147 international units per liter (IU/L). Some labs may use a slightly different range, such as 30 to 120 IU/L.

Children and adolescents tend to have higher ALP levels than adults due to bone development. Also, there might be slight differences between males and females, particularly during puberty and older age. If your results are outside of that range, your doctor can help you understand what it means in the context of your overall health.

Why is the ALP Blood Test Done?

Your doctor may order an ALP test alongside other tests to get a clearer picture of your health. Abnormalities in ALP in blood tests can reveal issues with certain organs, especially in the presence of prominent symptoms outside inherent or natural triggers. 

For instance, ALP can be elevated during periods of rapid bone growth (such as during childhood) or pregnancy. However, high ALP levels (above 147 IU/L) can also signal a range of conditions, including:

• Liver damage or disease: ALP levels often rise when the liver is damaged or diseased⁽⁴⁾. This could be due to conditions like hepatitis (liver inflammation often due to viral infections), cirrhosis (liver scarring), or even liver cancer. 
• Blocked bile ducts: The liver produces bile, a fluid that aids in digestion. This bile flows through ducts to the small intestine. Gallstones (hardened deposits in the gallbladder) or other obstructions can hinder this flow, leading to a buildup of bile in the liver and a subsequent increase in ALP levels⁽⁵⁾.
• Bone diseases: Increased ALP can signal bone diseases such as Paget’s disease⁽⁶⁾ (where bones become abnormally large and weak), osteomalacia⁽⁶⁾ (softening of the bones), or bone tumors⁽⁷⁾.
• Cardiovascular disease: High ALP levels, particularly from the liver, can be associated with inflammation and metabolic syndrome, both of which are risk factors for cardiovascular disease. Additionally, some studies suggest that elevated ALP may contribute to the calcification of blood vessels⁽⁸⁾, a process that can lead to heart disease.

In contrast to high ALP levels, which are more common and often point to a problem, low ALP levels (below 44 IU/L) are less prevalent and usually less alarming. However, they can still point to certain underlying health issues.

Here are some potential causes of low ALP:

• Hypophosphatasia: This rare inherited disorder impairs bone and teeth development. It is caused by a deficiency in the tissue-nonspecific alkaline phosphatase isoenzyme (TNSALP)⁽⁹⁾, leading to inadequate bone mineralization.   
• Malnutrition: Severe malnutrition, especially deficiencies in zinc, magnesium, and vitamin B6, can lead to lower ALP levels. This is because these nutrients are essential for the production of ALP.   
• Hypothyroidism: An underactive thyroid gland can sometimes cause low ALP levels⁽¹⁰⁾. This is because thyroid hormones are one factor that influences bone metabolism.  
• Wilson’s disease: This is a rare genetic disorder that causes copper to build up⁽¹¹⁾ in the body, potentially affecting liver function and leading to low ALP levels.
• Celiac disease: In some cases, celiac disease, an autoimmune disorder triggered by gluten consumption, can lead to malabsorption and nutritional deficiencies⁽¹²⁾, contributing to low ALP.

It is rare to encounter low ALP in your blood tests. This is why it’s imperative to deal with it if you happen to have such a result, especially if other symptoms or risk factors for any of the conditions mentioned above are noted. 

How to Prepare for the ALP Blood Test

Generally, an ALP blood test requires minimal preparation. However, your doctor may provide specific instructions depending on your individual circumstances. You may need to fast for 8-12 hours if the ALP test is done simultaneously with other blood tests. For example, it could be an inclusion in the comprehensive liver profile blood test. This means you must avoid any food or drink except water.

Your doctor may also ask you to temporarily stop taking certain medications that could interfere with the test results. Be sure to inform your doctor about all medications, supplements, and herbal remedies you are taking, even over-the-counter ones. They will advise you on whether any adjustments are necessary before the test.

Also Read: Preparing for a Blood Test: Things You Should Do to Get the Most Accurate Results

Frequently Asked Questions

Is the ALP test painful?

An ALP test is a simple blood test that involves drawing a small blood sample from a vein in your arm. The procedure is similar to any other routine blood test. You may feel a slight prick or sting when the needle is inserted, but it is generally not considered painful. Most people report minimal discomfort, and any sensation is usually brief and subsides quickly.

How often should I get an ALP test?

How frequently you need an ALP test depends on your situation and why you’re getting it in the first place. Your doctor might order one if you show symptoms of liver or bone problems as part of figuring out what’s going on. If your levels are off, they might want to check them again later to see how things are progressing or if treatment is working.

Can I lower my ALP levels naturally?

Whether or not you can lower your ALP levels naturally depends entirely on the underlying cause of the elevation. If the increase is due to a benign cause like pregnancy or rapid growth, the levels will typically normalize on their own. However, if it’s related to a specific condition, addressing that condition is key. 

In some cases, lifestyle modifications like maintaining a healthy weight, avoiding alcohol, and quitting smoking can improve liver health and potentially lower ALP levels. For example, with bone-related conditions, ensuring adequate intake of calcium and vitamin D may be beneficial. 

The Bottom Line

While abnormal ALP levels can indicate a range of conditions, it’s crucial to remember that this test alone is not a definitive diagnosis.  Your doctor will always interpret your ALP results in conjunction with other blood tests, your medical history, and a physical exam to create a complete picture of your health. If you have any concerns about your ALP levels or overall health, don’t hesitate to discuss them with your doctor. They can provide personalized guidance and address any questions you may have.

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⁸ Chang CH, Liou HH, Wu CK. Moderate-severe aortic arch calcification and high serum alkaline phosphatase co-modify the risk of cardiovascular events and mortality among chronic hemodialysis patients. Ren Fail. 2025 Dec;47(1):2449572. doi: 10.1080/0886022X.2024.2449572. Epub 2025 Jan 12. PMID: 39801127; PMCID: PMC11731357.

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