What Is Alkaline Phosphatase?
Alkaline phosphatase (ALP) s an enzyme found in your body, mostly in your liver and bones. Small amounts of ALP are also in your digestive system, kidneys, and the placenta during pregnancy.
Scientists don't completely understand what alkaline phosphatase does for your body. It may help build bones and hard tissue (like your teeth) and transport phosphates and other molecules in your intestines in addition to other important bodily functions.
Alkaline phosphatase and fatty liver
Fatty liver, or fatty liver disease, refers to a buildup of fat in your liver. ALP is one of the markers that can be used to diagnose the disease, but it’s not the only one that guides a doctor to the diagnosis.
There are two kinds of fatty liver disease:
- Metabolic-associated steatotic liver disease (MASLD) is when fat accumulates in your liver, and it is often caused by high cholesterol, type 2 diabetes, insulin resistance, or having a body mass index (BMI) over 30. It was formerly called nonalcoholic fatty liver disease (NAFLD).
- Alcoholic fatty liver disease, which is also known as alcoholic steatohepatitis, is due to drinking too much alcohol over time.
ALP Blood Test
An alkaline phosphatase (ALP) test measures the amount of this enzyme in your blood to help diagnose certain health problems. If you show signs of liver disease or a bone disorder, your doctor may order an ALP test.
Sometimes it’s part of a group of tests called a routine liver panel or hepatic panel, which check how your liver is working. A comprehensive metabolic panel (CMP) will often test for ALP, too.
“The ALP test alone is not sufficient to make a definitive diagnosis,” says Neeral Shah, MD, a professor of medicine in gastroenterology and hepatology at University of Virginia. Additional tests and a clinical exam are needed to determine the underlying cause of abnormal ALP levels, he says.
When to Get an ALP Blood Test?
When your doctor orders a comprehensive metabolic panel (CMP) during an annual health checkup, it may include a general ALP blood test to make sure your alkaline phosphatase is within the normal range.
You may need regular ALP blood tests if you take vitamins or medications that affect your liver, like acetaminophen, or statins, which help lower cholesterol. Your doctor can let you know if that’s an issue with any of the drugs or herbal supplements you take.
If your doctor thinks your liver isn’t working well or you have a problem with your bones, an ALP blood test can help them find out what’s going on. It can also help them keep an eye on any existing health problems you have, including diseases that affect your bones and liver like cancer, hepatitis, and cirrhosis.
Don’t expect to get all your answers from the ALP test alone, warns Sean Ormond, MD, a pain management doctor from Arizona.
“The ALP test is a helpful clue, but it doesn’t give us a full picture. It tells us something might be wrong, but we need to do more tests to figure out exactly what’s going on,” Ormond says. “If you have pain and abnormal ALP results, we'll likely need further tests to pinpoint whether it's your liver, bones, or something else causing the issue.”
How Is an ALP Blood Test Done?
The lab will need a small amount of blood to perform the test.
The person in charge of taking your blood will place a tight elastic band, called a tourniquet, around your upper arm. This makes your veins swell with blood.
The lab tech will clean an area of your skin with a germ-killing solution. (It might be a spot inside your elbow or the back of your hand). You’ll feel a small prick when the needle goes into your vein. The blood flows into a small vial attached to the needle.
When the test is done, the lab tech will take the tourniquet off, and you’ll get a bandage on the spot where the needle went in. It takes only a few minutes.
Taking blood samples is usually very safe. Some things that might happen after the test include a bruise at the spot where the needle went in and a little dizziness. There’s also a slight chance of infection.
How to Prepare for an ALP Blood Test
You may have to limit food and liquids (other than water) for 10-12 hours before the test. Some medicines interfere with the results, so make sure your doctor knows about all drugs you take, including over-the-counter medicines, vitamins, and supplements.
Tell your doctor if you're pregnant because ALP in the placenta can increase the amount of the enzyme in your blood.
ALP Test Results
It generally takes one or two days for results to come back from the lab. Your ALP test report will show you:
- What was measured
- The levels in your blood
- The normal range
- If your levels were high, low, or normal
ALP normal range
The normal range for alkaline phosphatase depends on the lab where you have your blood work performed. Normal ALP ranges can be 44-147 international units per liter (IU/L), or 30-120 IU/L. Your lab report will let you know what it considers normal.
High alkaline phosphatase
Higher-than-normal ALP levels for your age and sex may not necessarily mean you have a health problem that needs treatment, especially if your levels are only slightly elevated.
Elevated alkaline phosphatase can be related to several things:
- Children and teens have elevated levels because their bones are still developing.
- Males (and those assigned male at birth) ages 15-50 usually have slightly higher ALP levels.
- ALP levels may go up in older age.
- A bone break can temporarily increase ALP.
- For some people, eating a fatty meal before an ALP blood test can cause higher-than-normal levels.
- ALP may go up by as much as three times when you’re pregnant. Your doctor may monitor your ALP levels while you’re expecting.
- Smoking has been linked to high ALP levels.
If your ALP level is very high, your doctor may repeat the ALP test while you’re fasting, says Edward Oldfield IV, MD, a gastroenterologist in Virginia.
Your doctor may order another blood test, called an ALP isoenzyme test, to determine the organ in your body that’s releasing the high levels of alkaline phosphatase.
Your doctor may also want to check a gamma-glutamyl transpeptidase (GGT), which is more specific to the liver.
“If the ALP and the GGT are elevated, this suggests a liver origin. If the GGT is normal, then the elevation is likely not from the liver,” Oldfield says.
Imaging studies may be used to evaluate the larger bile ducts to make sure they're not blocked. The doctor may do more blood tests to rule out liver disease or suggest that they remove a small piece of liver tissue surgically (a procedure called a biopsy), Oldfield says.
Elevated alkaline phosphatase levels can be caused by conditions such as:
- Blocked bile ducts
- Liver cancer
- Cirrhosis
- Hepatitis
- Narrowing of the bile ducts
- Mononucleosis
- Cholestasis of pregnancy (a liver condition that occurs late in pregnancy)
- Untreated celiac disease
- Certain drugs or toxins
- Inflammatory conditions such as primary biliary cholangitis (PBC) or primary sclerosing cholangitis (PSC)
An elevated ALP isoenzyme test can indicate issues like:
- Cancers that have spread to your bones
- Paget’s disease, which affects how bones grow
- Vitamin D deficiency
- Some thyroid conditions
What level of alkaline phosphatase is dangerous?
The high end of the normal ALP range is 147 IU/L, but laboratories can differ slightly in terms of what they consider a normal range. Other organizations say that 30 to 120 IU/L is considered normal. Generally, anything over 147 IU/L can be considered high.
There’s no known research that a certain level is dangerous, per say. Sepsis, which can be dangerous or life-threatening, can cause some cases of high ALP (over 1,000 IU/L).
Elevated alkaline phosphatase in pregnancy
During pregnancy, the placenta produces alkaline phosphatase. Levels of ALP can get up to three times the normal limit.
Experts say that an abnormal elevated level, or rising levels, can indicate problems with the placenta. High ALP may also be a sign that you may experience preterm delivery or have an infant born large for gestational age, some research indicates.
During the third trimester of pregnancy, levels may be from 38-229 IU/L. Your doctor may monitor your ALP levels during your pregnancy if they are elevated. ALP levels generally go back to normal after birth, notes David N. Assis, MD, an associate professor of medicine in digestive diseases at the Yale School of Medicine.
Low ALP
Having lower-than-normal ALP levels is less common than having high levels.
You may have low levels of ALP if you have:
- An underactive thyroid gland (hypothyroidism)
- Low red blood cells due to a vitamin B12 deficiency (pernicious anemia)
- Zinc or magnesium deficiency
- Hypophosphatasia (HPP)
- Wilson’s disease, a rare genetic disorder that causes the body to make too much copper
Some medications, including hormonal birth control, can sometimes lower your levels of ALP.
What Are the Symptoms of High Alkaline Phosphatase?
If the ALP is elevated and it is reflecting liver and biliary disease, Assis says you may also have fatigue and itching. Many people don’t have symptoms of high ALP at all, Assis says.
If you have high ALP, doctors will likely evaluate you whether or not you have symptoms, Assis adds.
Liver disease symptoms can include:
- Nausea and vomiting
- Appetite loss
- Fatigue
- Weakness
- Swelling in your ankles and legs
- Dark-colored pee and/or light-colored poop
- Frequent itching
- Jaundice, which causes your skin and eyes to turn yellow
- Swelling and/or pain in your abdomen
Bone disorder symptoms can include:
- Bone pain
- Broken bones
- Inflammation and arthritis in your joints
- Unusually shaped bones and/or enlarged bones
What causes alkaline phosphatase levels to be high?
If your ALP blood test results come back high, it may mean that you have a liver issue or a bone disorder.
The ALP test is an indicator of potential health issues, but additional tests and clinical evaluation are necessary to determine the underlying cause of abnormal ALP levels, Shah explains. “After that [initial ALP blood test], it may require other lab testing or radiology imaging to help determine the cause of the abnormality."
If your doctor wants to find out the cause of high ALP, they may do an ALP isoenzyme test or a full panel of liver function tests. Liver problems and bone disorders create different types of ALP. The isoenzyme test can tell which type of ALP is high and where it’s coming from. For example, if the isoenzyme test shows the ALP is from your liver, your doctor will try to diagnose the liver issue.
High ALP in your liver can be a sign of:
- Blockages or narrowing in your bile ducts
- Cirrhosis, which is when scarring affects how your liver works
- Liver inflammation, or hepatitis
- Mononucleosis, which can sometimes cause swelling in the liver
- Cholestasis of pregnancy
High ALP in your bones may be a sign of:
- Bone metastasis, when cancer spreads to bones
- Paget’s disease of the bone, or osteitis deformans
- Osteogenic sarcoma, a cancer that starts in your bones
- Fracture healing
- Untreated celiac disease
- Hyperparathyroidism, which occurs when your calcium levels go up
- Hyperthyroidism, when your body makes too much thyroid hormone
- Osteomalacia, which weakens bones
If your ALP levels are only mildly elevated – less than a 50% increase – your doctor may not do an extensive evaluation.
What foods to avoid if alkaline phosphatase is high
There’s not much research published on foods to steer clear of if you have high ALP levels.
If elevated ALP levels are from your liver, you may want to avoid foods known to be bad for your liver. Consult your doctor.
Some foods that aren’t good for optimal liver health include:
- Fatty foods
- Sugar
- Alcohol
- Processed foods
If you have high ALP in your bones, ask your doctor if there are foods to avoid. These tips about foods that can negatively impact bone health may help:
- Limit meat, salty foods, caffeine, coffee, tea, soft drinks, and alcohol.
- Time when you take wheat bran, which may lower absorption of calcium in other foods you eat with it.
- Don’t skip spinach, but don’t rely on it for calcium, as the green is high in oxalates that can block calcium absorption.
- Soak beans in water first to lower phytates, which interrupt your ability to absorb calcium.
What Are the Symptoms of Low Alkaline Phosphatase?
Low ALP can point to several health issues. You may be able to take supplements to replenish levels if your low ALP is caused by a vitamin or mineral deficiency. Low ALP is often found in people with the rare disease hypophosphatasia (HPP), which causes symptoms such as tooth loss and bone and joint pain, among other symptoms, which vary based on the age of diagnosis. In that case, you may need more extensive treatments.
How to Increase Alkaline Phosphatase
Some research suggests a diet rich in phosphorus, healthy fats, zinc, vitamin B12, and vitamin A can raise alkaline phosphatase levels if you have a zinc or magnesium deficiency.
How to Lower Alkaline Phosphatase
There’s not a lot of definitive research on how to lower ALP levels. A small study on people with diabetes found that omega-3 fatty acids reduced their levels of ALP, and the supplement helped ALP levels go down in people with MASLD. Coffee has also been linked with lower ALP levels, as has drinking milk.
Takeaways
High or low alkaline phosphatase levels don’t always mean you have a health problem. But abnormal levels can signal something more serious. It’s critical to see your doctor after an abnormal result to receive an accurate diagnosis, if there is one.
“If your ALP levels come back off, it doesn’t automatically mean something serious,” notes Ormond. “The next step is to figure out why that might be happening. Your doctor will probably suggest additional tests, like liver function tests or imaging (like X-rays or MRIs), to get a clearer picture. This helps us understand if the issue is in your liver or bones, or maybe something else entirely.”
Alkaline Phosphatase FAQs
When should I worry about alkaline phosphatase?
Your doctor will let you know what high or low alkaline phosphatase levels mean. But you should seek medical help if you have symptoms like yellowing skin or pain in your bones or joints. Those could be a sign of liver or bone disease.
What causes alkaline phosphatase levels to change?
Medical conditions that affect the liver and bones can change your ALP levels. Factors such as recent bone fractures, pregnancy, dietary choices, certain medications, and hormonal birth control can also cause your ALP levels to go up or down.
What is alkaline phosphatase in liver damage?
Elevated alkaline phosphatase can be a sign your liver isn’t working the right way. High levels of ALP may indicate blocked bile ducts (tubes that connect your liver and gallbladder to the rest of your gut), liver inflammation or scarring, or an infection that causes liver swelling.
