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Alkaline Phosphatase

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

A blood test that measures the level of alkaline phosphatase, an enzyme mainly found in the liver and bones.

Quick summary

{"ALP is an enzyme primarily produced in the liver and bones","Elevated ALP may indicate liver disease, bone disorders, or other conditions","The test requires a simple blood draw, typically fasting for 8-12 hours","Normal range varies by age and gender","Your doctor will interpret results based on your overall health and other test results"}

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

Key facts at a glance

LOINC
6768-6
Short code
ALP
Synonyms
—
Category
liver
Sample
serum
Container
Serum Separator Tube (SST) or Plain Red Top Tube
Units
U/L
Ref low
44
Ref high
147
Critical range
20 U/L – 400 U/L
Fasting
false
Population
adult
Sex
all
Age range
0–120 years
Method
enzymatic-kinetic
CPT
84075
SNOMED
102589004
Specimen volume
3.5 mL
Stability
Room temperature: 7 days, Refrigerated (2-8°C): 7 days, Frozen (-20°C or below): 30 days. Avoid repeated freeze-thaw cycles.
Hemolysis max
50
Lipemia max
100
Icterus max
20
TAT
1–4 hours

What is the Alkaline Phosphatase Test?

The alkaline phosphatase (ALP) test is a blood test that measures the amount of alkaline phosphatase in your blood. Alkaline phosphatase is an enzyme—a type of protein that helps speed up chemical reactions in your body. This enzyme is found throughout the body, but it is primarily produced in the liver, bones, intestines, and kidneys.

Why is this Test Performed?

Your doctor may order an ALP test as part of a routine liver function panel or if you have symptoms suggesting liver or bone problems. Common reasons include checking for liver damage, evaluating bone disorders such as Paget's disease or osteomalacia, diagnosing bile duct obstruction, or monitoring the effectiveness of treatments for liver or bone diseases.

How is the Test Done?

A healthcare professional will draw a small blood sample from a vein in your arm using a needle. The sample is then sent to a laboratory for analysis. You may be asked to fast for 8-12 hours before the test, as food can affect ALP levels. It's important to inform your doctor about any medications, vitamins, or supplements you are taking, as some medications can influence test results.

Understanding Your Results

ALP levels are measured in units per liter (U/L). Normal adult ranges are typically between 20-140 U/L, but this can vary based on age, gender, and the laboratory performing the test. Children and adolescents normally have higher ALP levels due to bone growth. Your doctor will interpret your results in the context of your overall health, symptoms, and other test results.

Reference range

Adult reference range: 44-147 U/L. Note: Reference ranges vary by age, sex, and laboratory methodology. Children and adolescents typically have higher ALP due to bone growth activity. In pregnancy, ALP levels may be elevated in the third trimester due to placental isoenzyme.U/L

Specimen: serum

No fasting required for standard testing. Avoid heavy meals before collection if possible to minimize lipemia. Inform laboratory of any medications including antacids, antibiotics, or hepatotoxic drugs.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

ALP

Part of panels

female-pregnancy-healthlftlft-extendedmale-comprehensive-healthfemale-comprehensive-healthelderly-comprehensive-healthliver-disease-screeningabdominal-pain-workuphealth-check-comprehensivecmphealth-check-executive

Frequently asked questions

Does the ALP test require fasting?
Yes, you are typically asked to fast for 8-12 hours before the test. Some laboratories may not require fasting, so follow your doctor's specific instructions.
What happens if my ALP level is high?
A high ALP result doesn't necessarily mean you have a serious condition. Your doctor will likely order additional tests to determine the cause, which may include imaging studies or more specific blood tests. Common causes range from harmless (such as bone healing after a fracture) to conditions requiring treatment.
Can medications affect ALP test results?
Yes, certain medications can affect ALP levels. These include birth control pills, some antibiotics, epilepsy medications, and anti-inflammatory drugs. Always inform your doctor about all medications and supplements you are taking.
Is the test dangerous?
The risks are minimal and similar to any blood draw. You may experience slight bruising, bleeding, or dizziness. These side effects usually resolve quickly.
  1. 1
    MedlinePlus - Alkaline PhosphataseSource
  2. 2
    Mayo Clinic - Alkaline PhosphataseSource
  3. 3
    Lab Tests Online - Alkaline PhosphataseSource

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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