Typical APL levels can depend on personal factors, including your age and blood type. Atypical ALP levels can indicate health concerns, such as liver, gallbladder, or bone issues.

An alkaline phosphatase (ALP) test measures the amount of alkaline phosphatase, an enzyme in your bloodstream that is found throughout the body, especially in the liver and bones.

The test requires a simple blood draw and is often included as part of a comprehensive metabolic panel (CMP) or liver function testing.

Abnormal ALP levels may be linked to conditions affecting the liver, bile ducts, or bones, although results can be influenced by factors such as age, pregnancy status, and the laboratory’s reference range.

Your healthcare professional will interpret your ALP result alongside your symptoms, medical history, and other test results to determine whether further evaluation is needed.

ALP is an enzyme that helps break down proteins and plays a role in several processes throughout the body. It exists in different forms, called isoenzymes, depending on where it is produced.

The liver and bones are the primary sources of ALP in the blood. Smaller amounts are also produced in the intestines, pancreas, and kidneys. During pregnancy, the placenta also produces ALP, which can contribute to higher levels in the bloodstream.

Because ALP is produced in several areas of the body, changes in ALP levels may indicate conditions in different organs and tissues.

Children and adolescents typically have higher ALP levels than adults because their bones are actively growing and developing. Reference ranges may also vary slightly between laboratories depending on the testing methods used.

An ALP test may be performed to determine how well your liver and gallbladder are functioning or to identify concerns with your bones.

Liver and gallbladder

Checking ALP levels in the blood is a routine part of liver function and gallbladder tests. Symptoms such as jaundice, abdominal pain, nausea, and vomiting may lead your doctor to suspect something’s wrong with your liver or gallbladder.

The ALP test can be helpful in identifying conditions such as:

You may also need an ALP test if you’re taking a medication that has the potential to damage your liver, such as acetaminophen (Tylenol). Measuring ALP is one way to detect that damage and is typically performed alongside other liver function tests.

Bones

The ALP test can be helpful in the diagnosis of bone concerns, such as:

  • rickets, a weakening or softening of the bones in children that’s most commonly due to a significant deficiency of vitamin D or calcium
  • osteomalacia, a softening of the bones in adults, usually due to significant vitamin D deficiency, but also possibly due to the body’s inability to process and use vitamin D properly
  • Paget’s disease of the bone, a condition causing serious concerns with bone destruction and regrowth

ALP testing may also help detect cancer tumors, unusual bone growth, or vitamin D deficiency. It can also be used to check the progress of treatment for any of the above conditions.

Having blood drawn for an ALP test is routine. It’s usually combined with other liver and kidney function tests.

You may have to fast for 10 to 12 hours before the test. However, you most likely won’t need to do anything else to prepare in advance.

If the test results are inconclusive, your doctor may order a follow-up test.

Eating can interfere with your ALP levels. Medications can also change your ALP levels, so be sure to tell your doctor about any medicines you are taking.

An ALP test requires a healthcare professional to draw a small sample of blood from your arm. This is done in your doctor’s office or in a clinical lab.

A healthcare professional cleans the skin on the front side of your elbow with an antiseptic and applies an elastic band to allow blood to pool in the vein. They then insert a needle into the vein to draw blood into a small tube. The process is quick and typically causes little pain or discomfort.

The blood sample is collected in a tube and analyzed by a laboratory. The results may first go to your ordering physician or healthcare professional. This typically takes 1 to 2 days. Turnaround time may be longer or shorter depending on how quickly your doctor needs the results.

When your ALP test results are available, your doctor will discuss them with you and suggest what to do next.

High levels

Higher-than-normal levels of ALP in your blood may indicate a health concern with your liver or gallbladder. This could include a blockage in your bile ducts, gallstones, cirrhosis, liver cancer, and some forms of hepatitis.

High levels may also indicate a concern related to the bones, such as rickets, Paget’s disease, bone cancer, or an overactive parathyroid gland.

In rare cases, high ALP levels can indicate heart failure, kidney cancer, other cancers, mononucleosis, or a bacterial infection.

However, high ALP levels are not always a sign of disease. ALP levels are typically higher in children and adolescents because their bones are growing, and they may also increase during pregnancy.

Levels can also rise with aging, particularly in women, after eating a fatty meal, or due to a rare inherited condition called benign familial hyperphosphatasemia, which causes elevated ALP without an underlying health problem.

Low levels

Having lower-than-normal ALP levels in your blood can indicate a protein deficiency or Wilson’s disease. It may also signal malnutrition, which could be caused by celiac disease or an insufficient amount of certain vitamins and minerals.

Low ALP can also indicate a rare condition called hypophosphatasia. This causes fragile bones that are easily fractured and slow to heal.

Interpreting the results

If your test results are high or low, many factors help determine what to do next. If your levels are only mildly elevated or a bit low, your doctor may wait a while and then retest to see if they return to normal.

Your doctor also considers:

  • Other test results. Because an ALP test is often done as part of a panel, your doctor will take into account other enzyme levels.
  • Your current overall health. If you have symptoms that still need explaining or point to a diagnosis, your doctor will use these to interpret your ALP results.

ALP tests are generally accurate, but they only show part of the picture. A medical professional may need to perform additional tests to provide a diagnosis and treatment plan.

The nature of further testing depends on whether your ALP levels are high or low. Your doctor may want to find the source of high ALP levels or explain why ALP is low. Follow-up tests might include:

  • isoenzyme tests (to determine levels from the liver and bones)
  • diagnostic imaging of liver and gall bladder
  • vitamin and mineral levels
  • organ function tests

Your doctor can work with you to uncover why your ALP test results are out of range, and whether that’s a cause for concern.

There are very few risks associated with having your blood drawn.

You may experience some bruising around the puncture site, but this can be avoided by putting pressure on the wound.

In rare cases, phlebitis (inflammation of the vein) may develop. If you experience this complication, apply a warm compress until the swelling goes down.

Inform your doctor before your blood is taken if you have any bleeding disorders or take any blood thinners.

An alkaline phosphatase (ALP) test is a simple blood test that measures the amount of ALP in your bloodstream. It is commonly included in routine blood work, and results are typically available within a few days, depending on the laboratory.

ALP levels outside the typical reference range do not always indicate a health problem, but they may be associated with conditions affecting the liver, bile ducts, bones, or other areas of the body.

Your healthcare professional will consider your overall health, symptoms, and other test results when determining whether additional testing or follow-up is needed.