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Published: July 31, 2026Updated: August 10, 2026

A blood test that measures the level of alkaline phosphatase, an enzyme found in various tissues including the liver, bones, and intestines.

Quick summary

{"Alkaline phosphatase (ALP) is an enzyme produced by the liver, bones, and intestines","This test helps doctors evaluate liver function and bone health","Elevated or decreased ALP levels may indicate liver disease, bone disorders, or other medical conditions","The test is performed on a blood sample, typically drawn from a vein in your arm","Results are interpreted together with other liver tests for a complete picture"}

Medically reviewed by WellAlly Editorial TeamLast reviewed August 10, 2026Editorial policy

Key facts at a glance

LOINC
15148-0
Short code
ALP
Synonyms
ALP Fld-cCnc
Category
chemistry
Sample
serum
Container
Serum separator tube (SST) or plain red-top tube
Units
not specified
Ref low
44
Ref high
147
Critical range
— – 500 not specified
Fasting
false
Population
adult
Sex
all
Age range
18–100 years
Method
Colorimetric spectrophotometric assay using p-nitrophenyl phosphate (PNPP) as substrate, IFCC recommended method
CPT
84075
SNOMED
27090006
Specimen volume
2-3 mL of blood
Stability
Room temperature: 7 days; Refrigerated (2-8°C): 7 days; Frozen (-20°C): 3 months. Avoid repeated freeze-thaw cycles.
Hemolysis max
50
Lipemia max
300
Icterus max
20
TAT
4–24 hours
Order
routine

What is the Alkaline Phosphatase Test?

The Alkaline Phosphatase (ALP) test is a blood test that measures the amount of alkaline phosphatase enzyme in your blood. Alkaline phosphatase is a type of enzyme found in various tissues throughout your body, including the liver, bile ducts, bones, intestines, and kidneys. This test is commonly part of a comprehensive metabolic panel or liver function test.

Why Do I Need This Test?

Your doctor may order an ALP test to: check liver function and detect liver diseases such as hepatitis or cirrhosis; identify blockages in the bile ducts; evaluate bone disorders like Paget's disease, osteoporosis, or bone cancer; monitor the effectiveness of treatments for liver or bone conditions; or investigate unexplained symptoms like jaundice (yellowing of skin or eyes), abdominal pain, or bone pain.

How Is the Test Performed?

A healthcare professional will draw a small blood sample from a vein in your arm using a needle. The blood is collected into a tube and sent to a laboratory for analysis. You do not need to fast before this test, though your doctor may instruct you to do so. The procedure only takes a few minutes and is generally well-tolerated with minimal discomfort.

Understanding Your Results

Normal ALP levels vary depending on age, sex, and blood type. Generally, the normal range is about 20 to 140 IU/L (international units per liter), but this can vary by laboratory. High ALP levels may indicate liver disease, bile duct obstruction, bone disorders, or certain medications. Low ALP levels are less common but can occur in malnutrition, zinc deficiency, or certain genetic disorders. Your doctor will interpret your results in context with other tests and your overall health condition.

Reference range

No established reference rangenot specified

Specimen: serum

No special preparation required

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Frequently asked questions

Do I need to fast before the ALP test?
Fasting is typically not required for an ALP test. However, follow your healthcare provider's specific instructions, as they may recommend fasting if other blood tests are being performed simultaneously.
What can cause false elevated ALP results?
Certain factors can temporarily increase ALP levels, including: recent bone growth or fracture healing (in children and adolescents), pregnancy (especially in the third trimester), consumption of fatty meals (if testing intestinal ALP), and certain medications such as antibiotics, anti-inflammatory drugs, or birth control pills. Always inform your doctor about all medications and supplements you are taking.
Is the ALP test dangerous?
The ALP test is a routine blood test with minimal risks. You may experience slight pain, bruising, or dizziness at the puncture site, but these symptoms are usually temporary and resolve quickly.
What happens if my ALP levels are abnormal?
Abnormal ALP results do not always indicate a serious condition. Your doctor will likely order additional tests to determine the cause, such as gamma-glutamyl transferase (GGT) test to assess liver-specific issues, or bone-specific ALP isoenzyme testing. They will consider your symptoms, medical history, and other test results to make an accurate diagnosis.
  1. 1
    MedlinePlus - Alkaline PhosphataseSource
  2. 2
    May Clinic - Alkaline PhosphataseSource
  3. 3
    Lab Tests Online - Alkaline PhosphataseSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 10, 2026. · Read our editorial policy