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A blood test that measures the heat-stable portion of alkaline phosphatase enzyme to help identify if elevated ALP originates from liver or bone.
{"Measures the liver-derived portion of alkaline phosphatase enzyme in blood","Helps distinguish between liver and bone as the source of elevated ALP","Commonly used when total ALP is elevated to determine the cause","Involves heating the sample to inactivate bone-derived ALP","Results help diagnose liver diseases, bone disorders, or other conditions"}
Key facts at a glance
- LOINC
- 43710-3
- Short code
- ALP heat stable or Heat-stable ALP
- Synonyms
- ALP heat stable SerPl Ql 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
- 50
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 18 years
- Method
- heat-stability
- CPT
- 84075 (Alkaline phosphatase, total) - may require add-on code for heat-stable fraction determination
- SNOMED
- 31315002 (Alkaline phosphatase measurement) or 271225004 (Heat stability test)
- Specimen volume
- 2-5 mL of serum
- Stability
- Room temperature: 24-48 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C or below): 30 days. Avoid repeated freeze-thaw cycles
- Hemolysis max
- 50
- Lipemia max
- 300
- Icterus max
- 20
- TAT
- 24–72 hours
- Order
- routine
What is this test?
The Alkaline Phosphatase (Heat Stable) test measures a specific form of alkaline phosphatase that remains active after the blood sample is heated. This heat-stable portion primarily comes from the liver, while bone-derived ALP is inactivated by heat. This test is used as a follow-up when total ALP levels are elevated to determine whether the source is liver or bone.
How is the test performed?
A healthcare professional will draw a small blood sample from a vein in your arm. The sample is then heated to a specific temperature (typically 56°C) for a set time, which inactivates the bone-derived ALP while preserving the liver-derived (heat-stable) portion. The remaining ALP activity is then measured.
Why might I need this test?
Your doctor may order this test if a routine chemistry panel shows an elevated total alkaline phosphatase level. Since ALP can come from both liver and bone, the heat stability test helps determine which organ is contributing to the elevated result, guiding further diagnosis and treatment.
How to prepare
No special preparation is typically required for this test. However, you should inform your doctor about all medications and supplements you are taking, as some medications can affect ALP levels. Fasting may or may not be required depending on your healthcare provider's instructions.
Reference range
Negative (Absent)not specified
No special preparation required
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings2
Frequently asked questions
What does a high heat-stable ALP mean?
What does a normal heat-stable ALP mean?
Can medications affect this test?
Is the test safe?
How long does it take to get results?
Sources
- 1
- 2
- 3
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.
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