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Alkaline Phosphatase Activity in Serum

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

This test measures the activity of alkaline phosphatase, an enzyme found in cells that help build and repair bones and liver tissue.

Quick summary

["ALP helps assess bone and liver health by detecting enzyme levels that may signal abnormalities."]

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

Key facts at a glance

LOINC
15014-4
Short code
ALPI/ALP ratio or Intestinal ALP %
Synonyms
ALP Intest CFr SerPl
Category
chemistry
Sample
serum
Container
Serum separator tube (SST) or plain red top tube
Units
not specified
Ref low
0
Ref high
0.2
Fasting
false
Population
adult
Sex
all
Age range
≥ 18 years
Method
Spectrophotometric enzymatic assay using p-nitrophenyl phosphate substrate
CPT
84075 (Alkaline phosphatase, total) - ratio calculation included
SNOMED
104131001
Specimen volume
1.0-2.0 mL serum minimum
Stability
Room temperature: 24-48 hours; Refrigerated (2-8°C): 5-7 days; Frozen (-20°C): 2-3 months
Hemolysis max
50
Lipemia max
300
Icterus max
20
TAT
2–24 hours
Order
routine

Why Is This Test Done?

Your doctor may order this test to check for conditions affecting bone growth, liver function, or metabolism. It can help diagnose or monitor diseases like osteoporosis, liver disease, or certain cancers.

What Does a High or Low Level Mean?

Elevated levels may suggest liver issues, bone disorders, or other metabolic conditions. Lower levels could indicate bone diseases or certain genetic disorders, though results vary by individual health and age.

Common Conditions Monitored

ALP is often used to monitor bone health in children and adults, especially those with conditions like rickets, Paget’s disease, or after treatments for bone-related cancers.

Sample Preparation and Testing

A blood sample is drawn, and the serum portion is tested for enzyme activity using a specialized lab method. Results are reported in units per liter (U/L) or other standardized measurements.

Reference range

0.0-0.2not specified

Specimen: serum

Fasting preferred (8-12 h); intestinal fraction rises after fatty meals

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Serum Alkaline Phosphatase (ALP)

Frequently asked questions

What factors might affect my ALP test results?
Several factors can influence ALP levels, including age, gender, medications (like steroids), pregnancy, or certain foods (e.g., dairy). Recent bone or liver activity, such as fractures or infections, can also temporarily alter results.
How soon will I get my results, and what should I do next?
Results are typically available within 1–3 business days. Your doctor will discuss them with you, explaining any changes in your health plan or next steps, such as further tests or lifestyle adjustments.
Can I prepare for this test in any way?
No special preparation is needed, but inform your doctor about all medications, supplements, or recent illnesses, as they may affect results.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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