Alkaline phosphatase levels charts Explained (in children, adults, & pregnancy)

Alkaline phosphatase is not a single enzyme. Instead, they are a group of isoenzymes present in different body tissues.

The majority of alkaline phosphatase present in your blood is derived from the liver and bones. However, these two sources are not the only sources of alkaline phosphatase.

Alkaline is present in:

• The liver.
• Bones.
• Intestinal and stomach mucosa.
• The kidneys.
• The placenta (its levels markedly increase during the third trimester of pregnancy).
• Germinal tissues (testicles and ovaries).
• It is also produced in excess amounts by some cancer cells, such as Hodgkin’sHodgkin’s cells.

The four main causes of elevated alkaline phosphatase are:

• Bile outflow obstruction from the liver (bile duct obstruction by a stone, tumor, stricture, or infection).
• Liver diseases.
• Bone diseases.
• Some types of cancer.

However, diseases are not the only cause of elevated alkaline phosphatase.

Other benign and physiological conditions may cause increased levels of alkaline phosphatases, such as:

• Pregnancy.
• Bone growth (children, young adolescents).
• Aging (alkaline phosphatase slightly and gradually increase in older ages).
• And others.

In this article, you will learn the different levels of alkaline phosphatase in:

• Adults.
• Children and adolescents.
• Pregnant women.
• Low alkaline phosphatase (lower limits by age) and its cause.
• The common causes of marked versus mild elevations in alkaline phosphatase.

1. Normal alkaline phosphatase levels charts (by age and gender).

The alkaline phosphatase normal ranges in adults range from 44 to 121 U/L (reference). These limits vary slightly from laboratory to laboratory.

In children and adolescents, the levels are often higher (due to bone growth) (reference).

The chart below illustrates normal alkaline phosphatase levels by age and gender (reference).

The vertical, black, and dotted lines represent adults’ upper limit of normal alkaline phosphatase.

The reference ranges for age and gender is in the table below (according to the famous U.S. Lab (labcorp®)).

The normal adult levels (121 U/L) in males and females may increase either moderately (less than four times the upper limit of normal (ULN)) or markedly (more than four times the ULN).

The causes are summarized in the table below (reference):

2. Alkaline phosphatase levels charts in children & young adolescents (0-16 years).

Children and young adolescents have significantly higher levels of alkaline phosphatase.

The elevations of alkaline phosphatase may reach 3 or 4 times the levels in adults.

The cause of significant elevations of alkaline phosphatase in children and young teenagers is bone growth. High bone turnover produces excess amounts of enzymes in the circulation.

The chart below shows the normal alkaline phosphatase levels in children and young adolescents (from 0-16 years) (reference).

Note the black horizontal line that represents the upper limit in adults. This line gives you an idea about the magnitude of elevations in alkaline phosphatase in children and young adolescents compared to adults.

Transient hyperphosphatemia of infancy and early childhood.

Sometimes, infants and young children (mainly between the ages of 6 months and two years) may experience periods of extreme elevations of alkaline phosphatase.

According to studies, 2-3% of infants and young children may have temporarily marked elevations of alkaline phosphatase (above 1000 U/L).

The exact cause is still unknown. But the condition is often asymptomatic and self-limiting after a few weeks or months.

3. Alkaline phosphatase levels chart during pregnancy (different trimesters).

The placenta produces significant amounts of alkaline phosphatase during pregnancy. As a result, pregnant women often have significantly higher levels.

The changes in prevalence in the last three months of pregnancy are due to larger, fully developed placenta.

In the third trimester, alkaline phosphatase levels up to twice the upper limit of normal (ULN) are considered normal (reference).

One study assessed the average levels of alkaline phosphatase during different trimesters of pregnancy, and here are the numbers:

• The first trimester: 68.5 U/L on average.
• The second trimester: 75.9 U/L.
• The third trimester:
  – 7th month: 126.7 U/L
  – 8th month: 178.8
  – 9th month: 234 U/L.

The chart below shows the dramatic increase of alkaline phosphatase levels during the third trimester of pregnancy (reference)

4. Low alkaline phosphatase levels: charts and causes.

The table below illustrates alkaline phosphatase’s lower limits by age and gender (reference).

Any alkaline phosphatase levels below these limits are considered low.

Possible causes of low alkaline phosphatase include (reference):

• Hypothyroidism (hypo-active thyroid gland): most patients will have normal alkaline phosphatase with hypothyroidism, but some will have low levels.
• Hypophosphatasia is a rare inherited disorder affecting bone and teeth development (learn more).
• Some medications: such as azathioprine, estrogens, estrogen/androgen combinations, and clofibrate).
• Pernicious anemia.
• Zinc deficiency.
• Malnutrition. 

MORE: 6 Low Alkaline Phosphatase Causes and Symptoms. 

5. Causes of High alkaline phosphatase.

When tissues that contain ALP become damaged or diseased, they can release more ALP into the blood, causing an increase in ALP levels. The following conditions may cause elevated alkaline phosphatase levels:

1. Liver Disease: This is one of the most common causes of elevated ALP. Conditions such as cirrhosis, hepatitis, liver cancer, or cholestasis (blocked bile ducts) can all lead to higher ALP levels.

2. Bone Disorders: Certain conditions that cause increased bone cell activity can lead to higher ALP levels. These include Paget’s disease (a condition that causes abnormal bone destruction and regrowth), osteomalacia (softening of the bones), or bone cancers. Fractures that are healing can also cause a temporary rise in ALP.

3. Gallbladder Disease: Gallstones or inflammation of the gallbladder (cholecystitis) can cause an increase in ALP, especially if they cause blockage of the bile ducts.

4. Infections or Abscesses: Certain severe infections, especially those affecting the liver or bile ducts, can lead to higher ALP levels.

5. Medications: Some medications can cause an increase in ALP, including certain antibiotics, cholesterol-lowering drugs, and medications used to treat seizures or mood disorders.

6. Malnutrition and Vitamin D Deficiency: These conditions can cause bone disease and increased bone cell activity, leading to higher ALP levels.

7. Certain Cancers: Besides liver and bone cancer, other cancers that have spread (metastasized) to the liver or bones can cause an increase in ALP.

8. Hyperparathyroidism: Overactivity of the parathyroid glands can lead to increased bone cell activity and higher ALP levels.

9. Pregnancy: In the third trimester of pregnancy, the placenta produces more ALP, leading to higher blood levels.

10. Heart Surgery: Following heart surgery, particularly coronary artery bypass grafting, ALP levels can increase temporarily.

These are the most common causes, but various other diseases can also lead to elevated alkaline phosphatase. Always consult your doctor if you have an abnormal lab result to determine the cause and appropriate treatment.

FAQs:

What is considered a high level of alkaline phosphatase?

The normal range for alkaline phosphatase in blood tests can vary slightly depending on the lab, but generally, it’s about 30 to 120 units per liter (U/L) for adults. If your level is above this range, it may be considered high, but you should always discuss the results with your healthcare provider to understand what these numbers mean in your specific case.

What is the most common cause of elevated alkaline phosphatase?

Liver disease and bone disorders are the most common causes of elevated alkaline phosphatase. Liver conditions such as hepatitis, cirrhosis, and blockage of the bile ducts can increase ALP levels. Similarly, bone conditions like Paget’s disease or bone cancer can cause elevated ALP. It’s important to note that increased levels of ALP aren’t definitive proof of these conditions. Further testing is usually required to pinpoint the exact cause.

Is alkaline phosphatase important?

Yes, alkaline phosphatase is an important enzyme in several tissues throughout the body, including the liver, bones, kidneys, and digestive system. It plays a vital role in several processes, including breaking down proteins, forming bone, and fat metabolism. Elevated levels of ALP in your blood can indicate liver disease or a bone disorder, which is why it’s often tested for in routine blood tests.

Is low ALP bad?

Just like high levels, abnormally low levels of alkaline phosphatase can also be a cause for concern. Certain nutritional deficiencies, such as a lack of zinc or vitamin C can cause low ALP levels. Additionally, it can also be a sign of certain medical conditions such as hypophosphatasia (a genetic disorder that affects bones and teeth), celiac disease, certain types of anemia, and Wilson’s disease (a condition that causes copper to accumulate in your liver, brain, and other vital organs). Always consult your healthcare provider if you have concerns about your ALP levels.