Alkaline phosphatase (ALP) blood test

An alkaline phosphatase blood test is a simple test to check the health of your bones, liver or other parts of your body.

Alkaline phosphatase (ALP) is a type of protein called an enzyme. It’s made mostly in the liver and bones. But it’s also found in the kidneys and intestines. During pregnancy, the organ that forms to help feed and give oxygen to the baby also makes ALP. That organ is called the placenta.

An ALP test usually isn’t done by itself. It’s often part of a group of tests called a liver panel or liver function tests. These tests look for many other substances related to liver health, and include:

• Alanine transaminase (ALT).
• Aspartate transferase (AST).

Types

There are two main types of alkaline phosphatase (ALP) blood tests.

• Standard ALP test. This blood test shows the total amount of ALP from all parts of the body.
• ALP isoenzyme test. Also called an ALP fractionation test, this blood test shows where the ALP is coming from, such as from the bones or liver. It may be done if a standard ALP test result comes back too high or too low. The test may not be available at all medical centers.

The ALP isoenzyme test is grouped by the body area being tested.

• Bone ALP. The body’s bone-forming cells make alkaline phosphatase. Levels of bone ALP may go up when bones are hurt, healing or growing.
• Liver ALP. Liver cells, especially those that line the bile ducts, make ALP. Levels of ALP go up when the liver is sick or hurt.

An alkaline phosphatase blood test, also called an ALP test, is often done as part of routine blood work to check your general health.

Your healthcare team may do an ALP test if you have symptoms of liver or bone disease. It also may be done if you have trouble with your intestines or parathyroid gland.

You may need an ALP test if you have symptoms such as:

• Unexplained tiredness.
• Nausea.
• Pain in the right upper belly.
• Yellowing of the skin or whites of the eyes.
• Bone pain.
• Frequent broken bones or changes in the shape of bones.

Liver conditions that an ALP test can help diagnose include:

• Blocked bile duct.
• Liver cancer or cancer that has spread to the liver.
• Liver failure.
• Liver swelling.
• Liver diseases such as hepatitis and cirrhosis.

Bone conditions that an ALP test can help diagnose include:

• Bone cancer or cancer that has spread to the bones.
• Bone diseases such as Paget’s disease of bone and osteomalacia.
• A rare genetic condition called hypophosphatasia (hi-poe-fos-fuh-TAY-zhuh), which makes bones and teeth very weak.

An ALP test is not used to diagnose weak, brittle bones, a condition called osteoporosis.

An ALP test also may be used to learn if you have:

• A type of cancer called Hodgkin lymphoma.
• Inflammatory bowel disease, including Crohn’s disease and ulcerative colitis.
• Not enough nutrients that the body needs to stay healthy, called malnutrition.
• Too much vitamin D.
• Overactive parathyroid gland.
• Underactive thyroid gland.

An ALP test also may be done to see how treatments for liver, bone or other diseases are working.

There’s little risk in getting an alkaline phosphatase blood test. As with any blood test, possible risks may include:

• Soreness or tenderness in the area where the blood is taken.
• Bruising near the area where the blood is taken.
• Bleeding.
• Fainting or feeling lightheaded.
• Infection of the area where the blood is taken. This is rare.

Most people don’t need to do anything special to get ready for an alkaline phosphatase blood test, also called an ALP test. But here are a few helpful things to keep in mind:

• Medicines. Some medicines and supplements may affect your ALP level. Tell your healthcare team about all the medicines and supplements you take. Include those bought without a prescription.
• Food and drinks. Eating a big meal just before the test can cause a small, brief rise in ALP. So you may be told not to eat or drink for a while before the test, especially if you’re having other blood work done. Ask your healthcare team if you need to stop eating or drinking for a short while before your ALP test.
• Alcohol. Do not drink alcohol for at least 24 hours before your test. Regularly drinking alcohol can raise your ALP level.
• Smoking. Some research says smoking may make bone ALP go up. But more research is needed. Ask your healthcare team if you need to stop smoking before an ALP test.
• Exercise. Intense exercise may make your ALP go up. Your healthcare team may ask you to skip the gym or a workout before your ALP test.

Before

An alkaline phosphatase (ALP) blood test is done in a medical office, clinic, lab or hospital. There are some at-home tests to check liver health, which may include an ALP test. But these tests aren’t widely available. There is no at-home ALP isoenzyme test.

If you’re anxious about needles or have fainted during a blood test, tell your healthcare team. Also tell the team if you have a bleeding disorder.

During

A small sample of blood is needed to do an ALP blood test. The test only takes a few minutes and may feel like a small pinch.

To do the test, the healthcare professional:

• Cleans the skin with alcohol.
• Uses a small needle to take blood from a vein, usually in your arm.
• Puts a bandage on to prevent bleeding.

After

You might have a small bruise or feel sore where the needle went in. That often goes away in a day or two. You can usually go back to your daily activities right away.

Your healthcare team gives you the test results. Most people get ALP results in about 1 to 2 days.

When looking at your ALP results, keep these things in mind:

• Small changes in your ALP number are common and usually nothing to worry about.
• One test result often doesn’t tell the whole story. Your healthcare team looks at how your ALP level changes over time.
• Exercise, what you eat, and stress can all make your ALP level go up or down a little.

Results of a standard ALP blood test are given in units per liter (U/L). A healthy ALP range is as follows:

• For males 19 and older: 40 to 129 U/L.
• For females 17 and older: 35 to 104 U/L.

Children and younger teens often have higher ALP levels due to bone growth. ALP levels also go up during pregnancy.

There is no standard range for ALP isoenzyme test results in younger people. A healthy range for adults 18 and older is as follows:

• Liver ALP isoenzyme: 15.8 to 71.9 U/L.
• Bone ALP isoenzyme: 12 to 56.7 U/L.
• Intestine ALP isoenzyme: Less than or equal to 12.6 U/L.

Note: Lab ranges may differ depending on the lab doing the test. Ask your healthcare professional what the target ALP goal is for you.

Very high ALP

The ALP level is considered very high if it’s more than four times higher than the top number in the range. So if the top number is 129 U/L, a very high ALP level would be about 500 U/L.

A completely blocked bile duct can make ALP levels rise to as much as 10 times the top number. If your ALP level is this high, more tests and treatment are needed right away.

Causes of High ALP

Liver conditions that can cause high ALP include:

• Blocked bile ducts.
• Liver cancer or cancer that has spread to the liver.
• Liver damage due to medicines, herbs or supplements, called drug-induced liver disease.
• Liver disease, including cirrhosis and metabolic dysfunction-associated steatotic liver disease (MASLD), formerly called nonalcoholic fatty liver disease (NAFLD).
• A liver transplant complication called organ rejection.

Bone conditions that can cause high ALP include:

• Bone cancer.
• Bone disease such as Paget’s disease of bone and osteomalacia.
• Broken bones that are healing.
• Cancer of the bone marrow, called myeloma.

Other things that can raise ALP levels are:

• Congestive heart failure.
• Crohn’s disease and ulcerative colitis.
• Hodgkin lymphoma.
• Life-threatening organ failure due to an infection, also called sepsis.
• Overactive parathyroid gland, also called hyperparathyroidism.
• Serious bacterial infection inside the belly area, called an intra-abdominal infection.

ALP levels also go up during pregnancy, especially in the last three months. This is expected and usually not a concern.

Causes of Low ALP

Low ALP may be caused by:

• A lack of vitamins, minerals and protein that the body needs, called malnutrition.
• Too much vitamin D.
• Not enough zinc or magnesium.
• A rare genetic condition called hypophosphatasia.
• Underactive thyroid, called hypothyroidism.

If your ALP level is out of range, your healthcare team may:

• Repeat the test in a few weeks or months.
• Order other blood tests or imaging tests such as a CT, MRI or bone scan.
• Talk with you about the medicines you take and how much alcohol you drink.
• Send you to a bone or liver specialist, if needed.

Once a cause for high or low ALP levels is found, your healthcare team talks with you about possible treatments. If you have questions about your test results or next steps, talk with your healthcare professional.