Skip to content

Alpheatstablecfrserplhs

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

A blood test that measures alkaline phosphatase, an enzyme found in the liver, bones, and other tissues, to help diagnose liver or bone disorders.

Quick summary

{"ALP is an enzyme primarily produced in the liver and bones","Elevated ALP may indicate liver disease, bone disorders, or bile duct blockage","The heat stability test helps determine if high ALP comes from liver or bone","Normal levels vary by age and gender, with higher levels in growing children","Certain medications, pregnancy, or heavy meals can affect ALP levels"}

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

Key facts at a glance

LOINC
43382-1
Short code
ALP heat stable, ALP isoenzyme heat stable, Heat-stable ALP fraction
Synonyms
ALP heat stable CFr SerPl HS
Category
chemistry
Sample
serum
Container
Serum separator tube (SST/Gold top) or plain red top tube
Units
not specified
Ref low
20
Ref high
40
Fasting
false
Population
adult
Sex
all
Age range
≥ 18 years
Method
heat-stability
CPT
84075
SNOMED
387713003
Specimen volume
2-3 mL serum minimum
Stability
Room temperature: 24-48 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C): 30 days; Avoid repeated freeze-thaw cycles
Hemolysis max
50
Lipemia max
300
Icterus max
20
TAT
4–24 hours
Order
routine

What is this test?

The Alkaline Phosphatase (ALP) test measures the amount of this enzyme in your blood. Alkaline phosphatase is produced by various tissues in the body, including the liver, bones, intestines, and kidneys. The heat stability method helps doctors determine whether elevated ALP is coming from the liver or from bone tissue, as different sources have different heat-stable properties.

Why is this test performed?

Your doctor may order an ALP test to: check for liver diseases such as hepatitis or cirrhosis; identify bile duct obstructions or gallstones; detect bone disorders including Paget's disease, osteomalacia, or bone tumors; monitor the effectiveness of treatment for liver or bone conditions; or investigate unexplained abdominal pain, jaundice, or bone pain.

How to prepare for the test

Follow these guidelines before your test: fast (no food or drink except water) for 8-12 hours as instructed by your doctor; avoid alcohol for at least 24 hours before the test; inform your doctor about all medications you're taking, as some drugs can affect ALP levels; let your healthcare provider know if you are pregnant, as pregnancy can increase ALP levels; and avoid vigorous exercise before the test, as strenuous activity may temporarily increase ALP.

Understanding your results

Normal ALP levels typically range from 20 to 140 IU/L, but the normal range varies by laboratory and depends on age, gender, and blood type. Higher than normal ALP may indicate liver problems (hepatitis, cirrhosis, bile duct obstruction), bone disorders (Paget's disease, bone healing fractures, osteomalacia), gallstones, or certain cancers. Lower than normal ALP is less common but may indicate malnutrition, zinc deficiency, or hypothyroidism. Your doctor will interpret your results based on your overall health and other test findings.

Reference range

20-40%not specified

Specimen: serum

Fasting preferred (8-12 hours)

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings2

Frequently asked questions

Does the ALP test hurt?
The test involves drawing a blood sample from a vein in your arm. You may feel a brief pinch or sting when the needle is inserted. Some people may experience minor bruising or soreness afterward, but serious complications are rare.
Can I eat before the ALP test?
Your doctor will provide specific instructions. Fasting for 8-12 hours is often recommended, but some facilities allow clear liquids. Follow your healthcare provider's instructions for accurate results.
What medications affect ALP levels?
Several medications can influence ALP results, including birth control pills, certain antibiotics, epilepsy medications, and some blood pressure drugs. Always inform your doctor about all medications, supplements, and herbal remedies you're taking.
Why would my doctor order the heat-stable ALP test?
The heat stability test helps distinguish between ALP originating from the liver versus bone. This is particularly useful when a patient has conditions affecting both organs or when the cause of elevated ALP is unclear from standard testing.
Is high always serious?
Not necessarily. Mild elevations can occur due to normal factors like growth in children, pregnancy, or recent bone healing. However, significantly elevated ALP usually requires investigation to determine the underlying cause.
  1. 1
    MedlinePlus - Alkaline PhosphataseSource
  2. 2
    Mayo 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