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What is Alkaline Phosphatase? Function & Normal Range

Written by Puya Yazdi, MD | Last updated:
Ana Aleksic
Evguenia Alechine
Medically reviewed by
Ana Aleksic, MSc (Pharmacy), Evguenia Alechine, PhD (Biochemistry) | Written by Puya Yazdi, MD | Last updated:

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Alkaline Phosphatase Blood levels

Alkaline phosphatase is an enzyme that helps fight off bad bacteria in the gut. It improves digestion, makes your bones strong, and keeps your mind sharp. Both high and low blood levels can be problematic. Read on to learn about its role in the body and whether your values are normal.

What is Alkaline Phosphatase?

Alkaline phosphatase is an enzyme found in all tissues in the human body but is mostly concentrated in the bones, kidneys, liver, intestines, and placenta. It exists in different forms, depending on where it originates from [1].

Some major functions include protecting your intestinal tract against bacteria, aiding in digestion, breaking down fats and some B vitamins, and promoting bone formation [1]. Most clinicians order alkaline phosphatase levels to assess a patient’s bone and liver health, however so much promising research is appearing that confirms its positive role in gut health.

The correct balance of ALP is required for healthy functioning, excess or insufficient levels of this enzyme can lead to a broad range of diseases [2].

Alkaline phosphatase is an enzyme found throughout the body. Balanced levels support digestion and bone health.

Alkaline Phosphatase Function

1) Supports Cognition

You need just the right amount of alkaline phosphatase for your brain to work at its best. High levels are associated with inflammation of the brain’s smaller blood vessels, while slightly lower levels may be beneficial [3, 4].

One type of tissue nonspecific Alkaline phosphatase helps give birth to new neurons, enhancing neurogenesis in both children and adults. Another type of intestinal alkaline phosphatase my complement brain health by reducing inflammation and balancing the “good” bacteria in the gut [5].

2) Keeps Bones and Teeth Healthy

Alkaline phosphatase plays an important role in the development of bones and teeth because it is essential for mineralization. Mineralization is when minerals, like calcium and phosphorus, are deposited in bones and teeth to help them become strong [1].

3) Maintains Cholesterol Levels

Pregnant women have higher blood alkaline phosphatase activity. Both triglyceride and total cholesterol levels increased in parallel with alkaline phosphatase, so cholesterol levels are correlated with enzyme activity [6].

Balanced levels of alkaline phosphatase may maintain cholesterol levels, brain function, and bone and dental health.

Normal Range for Alkaline Phosphatase

Generally, the total alkaline phosphatase (ALP) test is run to find all types of ALP in the blood to diagnose bone and liver disorders.

If ALP comes back high, the doctor may order the ALP isozyme test to see which specific type of alkaline phosphatase is elevated. The ALP isozyme test can distinguish between the bone and liver ALP.

The normal range of alkaline phosphatase in the blood is 20 to 140U/L, although this can vary from lab to lab. Some labs set the range at 30 to 130 U/L. Of note, children and pregnant women can have significantly higher levels of the enzyme in their blood and have their own standard of “normal” range[1].

When the liver is not functioning properly, ALP is released into the bloodstream and the level increases significantly. Additionally, any condition that affects bone growth or causes the increased activity of bone cells can increase ALP levels in the blood. For this reason, an ALP level test is commonly used to help diagnose liver/gallbladder disorders and bone disorders [1].

ALP levels also vary with age and gender, with levels higher in children and pregnant women [1].

Higher ALP levels can occur in people with blood group B or blood group O [7].

The normal range of alkaline phosphatase in the blood is 20 to 140 U/L. Doctors usually use this test to diagnose bone and liver disorders.

8 Benefits of Intestinal Alkaline Phosphatase

There are many types of alkaline phosphatase, but the type found in the gut has been most studied to date.

Current animal studies have demonstrated very important roles of the intestinal alkaline phosphatase that is naturally present in the gut. The enzyme interacts with the gut, the food we eat, and the microbes found in our body.

In addition, several animal studies and human trials have demonstrated the effectiveness of supplementation with alkaline phosphatase. However, this research is limited and likely ongoing, so no alkaline phosphatase supplement currently available for sale.

Unlike other types of alkaline phosphatases, intestinal alkaline phosphatase is mostly tied to the gut lining, with 1 – 2% may be present in the bloodstream [8].

Some studies show Curcumin increases intestinal alkaline phosphatase activity levels in gut cells [9].

Many types of alkaline phosphatase exist in the body. The type found in the gut is particularly important for health.

1) Protects Against Bacterial Infection in the Gut

Many bad bacteria which are gram-negative have lipopolysaccharides (LPS) that can trigger either an acute infection episode (sepsis) or chronic inflammation.

Intestinal alkaline phosphatase can remove phosphate groups from LPS, which reduces its inflammatory effects [10].

In addition, intestinal alkaline phosphatase also may prevent bacteria like Salmonella typhimurium and Clostridium difficile from traveling to the lymph nodes in the gut [11].

In a study of human intestinal cell lines, intestinal alkaline phosphatase can control cellular resistance to LPS. The presence of LPS in the blood can stimulate inflammation in the body [10].

Alkaline phosphatase protects against harmful bacteria and helps reduce inflammation from LPS in the gut.

2) Helps Restore Gut Bacteria After Antibiotics

Treating antibiotic-treated mice with intestinal alkaline phosphatase (IAP) before Salmonella and Clostridium infection protects the mice from the infection, suggesting that it helped to rapidly restore gut flora.

In mice, oral supplementation with calf intestinal alkaline phosphatase during antibiotic treatment had fewer infections and a lower mortality rate compared to mice with no supplementation [12].

Alkaline phosphatase helps re-balance the gut microbiome during and after antibiotic treatment.

3) Helps Repair Leaky Gut in Cystic Fibrosis Patients

Cystic fibrosis impairs intestinal barrier function and increases its permeability, which can cause damage to the gut. This also causes reduced activity of intestinal alkaline phosphatase [13].

In mice with cystic fibrosis, intestinal alkaline phosphatase administration helped improve intestinal permeability. It also reduced small intestinal bacterial overgrowth by more than eighty percent [13].

4) Helps Remove Toxic Microbial Chemicals

Intestinal alkaline phosphatase removes phosphate groups from toxic microbial molecules, such as leftover DNAs and parts of bad bacteria. This helps protect against inflammation [14].

Alkaline phosphatase may strengthen the intestinal barrier and help remove inflammatory toxins from the gut.

5) Slows Down Fat Absorption

Mice without intestinal alkaline phosphatase absorb fat very fast. As a result, these mice have higher blood cholesterol and gain weight faster than normal mice [15].

6) Helps Treat Kidney Injuries

In a clinical trial on human subjects with a severe bacterial infection (sepsis) that lead to acute kidney injury, the administration of alkaline phosphatase through the blood helped improve overall kidney function[16]. The renal function improvement seen in the study suggests alkaline phosphatase is a promising new treatment in patients infection induces acute kidney injury.

Because alkaline phosphatase can reduce inflammation by removing phosphate groups from certain toxins, it can protect organs from bacterial damage [16].

Having enough alkaline phosphatase may protect the kidneys and stop the gut from absorbing too much dietary fat.

7) Type 2 Diabetes

Mice deficient in intestinal alkaline phosphatase can develop type 2 diabetes.

Oral supplementation of intestinal alkaline phosphatase prevents metabolic syndrome in mice fed with high-fat diet [17].

Scientists studied the stools of 200 diabetic and 400 non-diabetic patients. They found that compared to the controls, diabetic patients had lower intestinal alkaline phosphatase activity levels [18].

Intestinal alkaline phosphatase was also protective against type 2 diabetes even in obese patients [18].

8) Helps Reduce Gut Inflammation

Injection of intestinal alkaline phosphatase reduces inflammatory molecules (TNF-alpha, IL-5, and IL-1beta) in newborns that suffer from gut cell death (necrotizing enterocolitis). However, the injection did not cure the necrotizing enterocolitis [19].

Alkaline phosphatase may reduce inflammation in the gut and may protect against type 2 diabetes.


Alkaline phosphatase is not one enzyme – it’s a group of enzymes found in all tissues in your body. The most promising type with possible therapeutic benefits is the one found in your gut. Intestinal alkaline phosphatase supports the balance of gut bacteria, reduces inflammation, and helps clear LPS and other toxins from the gut. Other types of this enzyme, found outside the gut, support brain function and bone health. Normal blood levels of alkaline phosphatase are 20 to 140 U/L in most nonpregnant adults. Doctors typically run this test to check for liver and bone disorders. Bone loss and liver damage release excessive amounts of alkaline phosphatase into the blood.

About the Author

Puya Yazdi

Puya Yazdi

Dr. Puya Yazdi is a physician-scientist with 14+ years of experience in clinical medicine, life sciences, biotechnology, and nutraceuticals.
As a physician-scientist with expertise in genomics, biotechnology, and nutraceuticals, he has made it his mission to bring precision medicine to the bedside and help transform healthcare in the 21st century. He received his undergraduate education at the University of California at Irvine, a Medical Doctorate from the University of Southern California, and was a Resident Physician at Stanford University. He then proceeded to serve as a Clinical Fellow of The California Institute of Regenerative Medicine at The University of California at Irvine, where he conducted research of stem cells, epigenetics, and genomics. He was also a Medical Director for Cyvex Nutrition before serving as president of Systomic Health, a biotechnology consulting agency, where he served as an expert on genomics and other high-throughput technologies. His previous clients include Allergan, Caladrius Biosciences, and Omega Protein. He has a history of peer-reviewed publications, intellectual property discoveries (patents, etc.), clinical trial design, and a thorough knowledge of the regulatory landscape in biotechnology. He is leading our entire scientific and medical team in order to ensure accuracy and scientific validity of our content and products.

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