Our body contains alkaline phosphatase (ALP), an enzyme found throughout. Blood tests for ALP measure the levels originating from the liver and bones. It is one of the tests in a liver panel. Elevated ALP levels in the blood may suggest liver disease or specific bone disorders.

What is an ALP test?

The ALP test measures the quantity of alkaline phosphatase (ALP) in your blood. Although ALP is present throughout your body, your liver and bones are the primary sources of ALP in your blood. Elevated ALP levels may suggest liver disease or specific bone disorders, but relying solely on an ALP test for diagnosis is insufficient.

There are two primary types of blood tests for alkaline phosphatase (ALP): a general ALP test (the more common one) and an ALP isoenzyme test.

Typically, a general ALP test is part of comprehensive metabolic panels (CMP) and liver function tests (LFT) in blood tests.

While an ALP test solely measures ALP levels in your blood, an ALP isoenzyme test can distinguish between different types of alkaline phosphatase based on their origin in your body.

If a previous test showed abnormal ALP levels, your healthcare provider might recommend an ALP isoenzyme test as a follow-up. Although this test offers more detailed information, it is technically challenging, expensive, and may not be available in all laboratories.

When is the Alkaline Phosphatase Test Done?

To screen for, monitor, or aid in the diagnosis of liver and biliary diseases, bone disorders, and other health conditions, your healthcare provider may request an alkaline phosphatase (ALP) blood test.

Screening involves checking for potential health issues before symptoms manifest. An ALP test is commonly part of a comprehensive metabolic panel (CMP) and liver panel, which healthcare providers often use in routine check-ups to screen for a broad spectrum of potential health problems.

If you have a liver or bone condition, or another health issue, your provider may order an ALP test, often as part of a panel, to monitor the progression of your condition—whether it is improving, worsening, or remaining stable, with or without treatment.

For diagnostic purposes, your provider may employ an ALP test when there are signs of potential liver or bone problems. Including an ALP test in a liver panel or CMP can also aid in diagnosing the cause of general symptoms such as fatigue. While a condition cannot be diagnosed based solely on ALP levels, they play a crucial role in the diagnostic process. The extent to which the ALP level deviates from the norm may provide insight into the type or severity of a condition.

Signs and symptoms of liver disease encompass:

• Jaundice, characterized by yellowing of the skin and the whites of the eyes.
• Abdominal (belly) pain and/or swelling, particularly on the right side.
• Easy bruising.
• Nausea and/or vomiting.
• Dark-colored urine and/or light-colored stool.
• Unexplained weight loss.
• Fatigue.
• Swelling in the arms or legs (edema).

Signs and symptoms of bone disorders include:

• Bone pain and/or joint pain.
• Enlarged and/or abnormally shaped bones.
• Increased frequency of bone fractures.

Test Preparation

If your alkaline phosphatase (ALP) test is included in a comprehensive metabolic panel (CMP), it is probable that you will be required to fast for 10 to 12 hours before undergoing the CMP blood test. Fasting entails abstaining from consuming any food or beverages except water.

Regardless, your healthcare provider will provide you with precise instructions when requesting a blood test. It is essential to adhere to these instructions diligently.

Normal Range of Results

The normal range for alkaline phosphatase (ALP) can differ from one laboratory to another. A frequently used reference range is between 44 to 147 international units per liter (IU/L).

Indeed, it’s crucial to recognize that normal alkaline phosphatase (ALP) levels exhibit variations based on age and gender. During childhood and puberty, ALP levels are commonly elevated due to ongoing bone growth and development. Between the ages of 15 to 50 years, ALP levels tend to be slightly higher in males compared to females. Additionally, ALP levels may increase again in old age.

Pregnant individuals may also experience higher ALP levels as ALP is present in the placenta. Furthermore, individuals in the process of healing from a bone fracture may exhibit elevated ALP levels. These nuances highlight the importance of considering age, gender, pregnancy, and specific health conditions when interpreting ALP test results.

High Alkaline Phosphatase

It is essential to recognize that elevated levels of alkaline phosphatase (ALP) can vary in severity. While a significantly high ALP level often indicates liver damage or a bone disorder, mildly elevated levels can result from various factors, not necessarily requiring immediate medical treatment. In the case of a mild elevation, healthcare providers typically opt for monitoring the levels over time to ensure they do not worsen.

Elevated ALP levels may suggest damage to the liver or the presence of a bone disorder. Liver damage produces a different type of ALP compared to bone disorders. If your test results indicate high ALP levels, additional tests, such as an ALP isoenzyme test, may be recommended to determine the source of the excess ALP.

High ALP levels in the liver may be indicative of the following conditions:

• Cholestasis of pregnancy: Common liver disease occurring late in pregnancy.
• Cirrhosis of the liver: Late-stage liver disease involving the replacement of healthy tissue with scar tissue.
• Hepatitis: Inflammation of the liver, with various types.
• Biliary atresia: Rare condition in infants involving blockage in the bile ducts.
• Biliary stricture: Narrowing of the bile duct.
• Biliary obstruction due to cancer: Cancers like cholangiocarcinoma and pancreatic head adenocarcinoma can block bile or pancreatic ducts.
• Mononucleosis (“mono”): Contagious infection causing liver swelling.

High bone ALP levels may be associated with the following conditions:

• Bone metastasis: Spread of cancer cells to the bones.
• Paget’s disease of the bone (osteitis deformans): Rare chronic bone disorder with excessive breakdown and regrowth.
• Osteogenic sarcoma: Cancer starting in the bones.
• Healing fractures.
• Hyperparathyroidism: Overproduction of parathyroid hormone, leading to elevated calcium levels.
• Hyperthyroidism: Overproduction of thyroid hormone.
• Osteomalacia: Disease weakening bones, often due to vitamin D deficiency.
• Untreated celiac disease: A gluten-related autoimmune disorder.

Understanding the underlying conditions associated with elevated ALP levels enables healthcare providers to determine appropriate diagnostic and treatment approaches.

Low  Alkaline Phosphatase

Indeed, having an abnormally low level of alkaline phosphatase (ALP) is less common than experiencing elevated levels. A low ALP level may suggest various underlying conditions, including:

• Malnutrition: Inadequate intake of essential nutrients, leading to a deficiency in ALP.
• Zinc deficiency: Insufficient levels of zinc in the body, which can impact ALP production.
• Magnesium deficiency: A lack of magnesium, an essential mineral, may contribute to low ALP levels.
• Hypothyroidism: An underactive thyroid gland, resulting in reduced ALP production.
• Rare genetic conditions:
• Hypophosphatasia: A rare inherited disorder characterized by defective bone mineralization and low ALP activity.
• Wilson disease: A genetic disorder that leads to copper accumulation in the body, affecting various organs including the liver, and potentially causing low ALP levels.

Monitoring ALP levels and identifying the underlying cause of abnormalities is crucial for accurate diagnosis and appropriate management. If there are concerns about ALP levels, consulting with a healthcare provider for further evaluation and testing is recommended.

References

1. Alki – Overview: Alkaline phosphatase, total and isoenzymes, serum. (n.d.). Retrieved from https://www.mayocliniclabs.com/test-catalog/overview/89503 
2. professional, C. C. medical. (n.d.). Alkaline phosphatase (ALP): What it is, causes & treatment. Retrieved from https://my.clevelandclinic.org/health/diagnostics/22029-alkaline-phosphatase-alp