Alanine Aminotransferase (ALT) Test
Measures alanine aminotransferase enzyme activity to help evaluate liver injury and other causes of elevated liver enzymes.
["An elevated ALT result may indicate liver injury, but it must be interpreted with your symptoms, medications, and other test results."]
Key facts at a glance
- LOINC
- 51540-3
- Short code
- A alternata IgG Ql
- Synonyms
- A alternata IgG Ql
- 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 liver cells and, to a lesser extent, in other organs such as the heart and skeletal muscle. The test measures ALT enzyme activity and is mainly used to evaluate possible liver injury.
Why might I need this test?
ALT may be checked during routine health examinations or when a clinician is evaluating abnormal liver-related symptoms, medication effects, alcohol use, or other conditions that could affect the liver.
How is the test performed?
The abbreviated code does not clearly identify the specimen or assay method. ALT is generally measured in serum or plasma using an automated enzymatic assay, which measures the rate at which the enzyme acts on a laboratory substrate.
How do I prepare for the test?
Fasting is usually not required for a routine ALT test, but follow the instructions provided by your clinician or laboratory. Tell the healthcare team about all medications and supplements you use, and avoid unusually heavy alcohol consumption or strenuous exercise before testing if possible because these can affect the result.
Reference range
Adult males: 7-56 U/L; Adult females: 7-43 U/LN/A
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?
Do I need to fast before an ALT test?
What should I do if my ALT is elevated?
Sources
- 1
- 2Lab Tests OnlineSource
- 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 17, 2026. · Read our editorial policy