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Alanine Aminotransferase (ALT) — Enzymatic Activity

Published: August 9, 2026Updated: August 17, 2026

Measures ALT enzyme activity in a laboratory sample to help evaluate liver injury and monitor liver conditions or medication effects.

Quick summary

["An elevated ALT result can signal liver-cell stress or injury, but it must be interpreted alongside other findings."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
7076-3
Short code
A alternata IgG Qn
Synonyms
A alternata IgG Qn
Category
liver
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
7
Ref high
56
Critical range
— – 500 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
84484
SNOMED
302773008
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What is this test?

Alanine aminotransferase, commonly called ALT, is an enzyme found in many tissues, with the liver containing a large amount. Measuring its activity helps assess liver-cell injury or stress.

Why might I need this test?

Clinicians may order ALT for routine health screening, when evaluating abdominal symptoms or suspected liver disease, or when monitoring medications that can affect the liver. It is often interpreted with other liver tests.

How is the test performed?

A laboratory uses a validated enzymatic assay to measure ALT activity in the specimen specified by your order. The abbreviated code does not clearly identify the specimen or reporting format, so confirm those details with the testing laboratory.

How do I prepare for the test?

Special preparation is often not required, although fasting may be requested when ALT is checked with other tests. Follow the laboratory's instructions, and do not stop prescribed medication unless your clinician advises you to do so.

Reference range

Adult males: 7-56 U/L; Adult females: 7-43 U/LN/A

Specimen: serum

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

ALT

Frequently asked questions

Is ALT the same as AST?
No. ALT and aspartate aminotransferase, or AST, are different enzymes that may both rise when liver cells are affected. Clinicians often interpret them together.
Does an abnormal ALT result always mean I have liver disease?
No. ALT can be elevated for several reasons, including medication effects, alcohol use, muscle activity, and nonalcoholic fatty liver disease. Additional testing is usually needed to determine the cause.
Should I be concerned if my ALT is high?
A high result should be discussed with your clinician, especially if it remains elevated or is accompanied by jaundice, dark urine, abdominal pain, or unusual fatigue. A single result cannot establish a diagnosis by itself.
  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 17, 2026. · Read our editorial policy