Bone-Specific Alkaline Phosphatase (B-ALP) Test
This blood test measures the bone-specific form of the alkaline phosphatase enzyme, which is produced by bone-forming cells. It helps your doctor evaluate your bone health, bone metabolism, and how well treatments for bone conditions are working.
{"This test measures bone-specific alkaline phosphatase (B-ALP), an enzyme produced by bone-forming cells","The Z-score compares your result to healthy people of the same age","It helps diagnose and monitor bone disorders like Paget's disease and osteomalacia","Elevated levels may indicate increased bone turnover or bone disease","The test requires a simple blood draw, usually fasting overnight"}
Key facts at a glance
- LOINC
- 74996-0
- Short code
- BALP, B-ALP, Bone ALP, bone-specific ALP
- Synonyms
- ALP Bone Z-score SerPl
- Category
- chemistry
- Sample
- serum
- Container
- Serum separator tube (SST/Gel tube) - 5 mL red-top or gold-top tube, or plasma collection tube (K2/K3 EDTA) for plasma samples
- Units
- not specified
- Ref low
- -2
- Ref high
- 2
- Critical range
- 3 not specified – 100 not specified
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–100 years
- Method
- Enzymatic assay using p-nitrophenyl phosphate (pNPP) substrate or chemiluminescent immunoassay (CLIA) for bone-specific isoform detection
- CPT
- 84080 (Alkaline phosphatase; isoenzyme, electrophoretic)
- SNOMED
- 314332006 (Bone alkaline phosphatase measurement), 187191003 (Serum alkaline phosphatase measurement)
- Specimen volume
- Minimum 0.5 mL serum/plasma, preferred 1.0 mL
- 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
- 40
- TAT
- 4–48 hours
- Order
- routine
What is this test?
The bone-specific alkaline phosphatase (B-ALP) test measures the amount of the bone-forming enzyme in your blood. Alkaline phosphatase (ALP) is an enzyme found throughout the body, but the bone-specific version is produced by osteoblasts – the cells responsible for building new bone. The Z-score result tells you how your level compares to the average for healthy people of your same age and sex.
Why is this test done?
This test helps healthcare providers assess how fast your body is building or breaking down bone. It is commonly used to diagnose conditions that affect bone metabolism, monitor treatment effectiveness for bone diseases, and evaluate unexplained bone pain or weakness. The test is particularly useful because it specifically measures bone-related ALP activity, rather than the liver version of the enzyme.
How to prepare for the test
Your healthcare provider may ask you to fast (not eat or drink except water) for 8-12 hours before the blood test. Certain medications and supplements can affect the results, so inform your doctor about all medications you are taking. Avoid taking calcium or vitamin D supplements before the test unless directed by your healthcare provider.
What to expect during the test
A healthcare professional will draw a small blood sample from a vein in your arm. The procedure only takes a few minutes and may cause minor discomfort or bruising at the injection site. There are no serious risks associated with this routine blood test.
Reference range
-2.0 to +2.0not specified
No fasting required; morning collection preferred for consistency with bone turnover markers
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Elevated bone-specific ALP levels may indicate: Paget's disease (abnormal bone breakdown and regrowth), osteomalacia or rickets (vitamin D deficiency causing soft bones), bone metastases or cancers, hyperparathyroidism (overactive parathyroid glands), or recent bone fractures that are healing. The Z-score helps determine if the elevation is significant by comparing your result to normal reference ranges.
Decreased or low normal levels may be seen in: hypophosphatasia (a rare genetic disorder affecting bone mineralization), malnutrition, magnesium or zinc deficiency, or chronic kidney disease. Your doctor will interpret your results in combination with other tests and your overall clinical condition.
This test is often ordered alongside other bone markers like calcium, phosphorus, vitamin D, and PTH (parathyroid hormone) to get a complete picture of bone health. Treatment monitoring for conditions like osteoporosis or Paget's disease may involve regular B-ALP measurements to track how well therapy is working.
Frequently asked questions
What does the Z-score mean?
Is this test different from a regular alkaline phosphatase test?
How long does it take to get results?
Do I need to stop taking my medications before this test?
Can exercise affect my bone-specific ALP levels?
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