Alanine Aminotransferase (ALT) Activity
Measures ALT enzyme activity, usually in blood, to help assess liver injury and monitor conditions or medicines that may affect the liver.
["An elevated ALT result may indicate liver cell injury but does not identify the specific cause."]
Key facts at a glance
- LOINC
- 58774-1
- Short code
- A alternata (rAlt a) 1 IgE Qn
- Synonyms
- A alternata (rAlt a) 1 IgE 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?
The alanine aminotransferase (ALT) test measures the activity of an enzyme found in many tissues, especially the liver. It is commonly performed on a blood sample.
Why might I need this test?
ALT may be checked during routine health visits, when symptoms suggest liver disease, or while taking medicines that can affect the liver. It may also be used to monitor treatment or the course of a known liver condition.
How is the test performed?
A blood sample is analyzed in a laboratory to measure ALT enzyme activity. The result is usually reported as an activity value and is interpreted with other liver tests and your clinical history.
How do I prepare for the test?
Fasting is usually not required, but follow any instructions from your healthcare professional. Tell the laboratory if you are taking medicines or supplements, because some can affect liver enzyme results.
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.
An elevated ALT level can occur when liver cells are injured, including with viral hepatitis, fatty liver disease, heavy alcohol use, or certain medicines. An abnormal result does not identify one specific condition and is interpreted alongside other liver tests and clinical findings. Occasionally, ALT may also be elevated because of significant injury or inflammation in muscles.
Short name
ALT test
Frequently asked questions
What does ALT measure?
Does a high ALT result mean I have liver disease?
Do I need to fast before this test?
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