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Alanine Aminotransferase (ALT) in Liver Cytosol

Published: August 9, 2026Updated: August 16, 2026

This test measures the level of alanine aminotransferase (ALT), an enzyme produced mainly in the liver that helps break down proteins. It helps assess liver health and detect damage.

Quick summary

["ALT helps identify liver problems by measuring how much enzyme leaks into your blood when the liver is injured."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
13175-5
Short code
Liver Cytosol Ab Ser Ql
Synonyms
Liver Cytosol Ab Ser Ql
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 ALT Tests for

ALT is primarily found in liver cells. When the liver is inflamed, damaged, or infected, some ALT leaks into the bloodstream, raising its levels. This can occur with conditions like hepatitis, fatty liver disease, or alcohol-related liver damage.

Why Your Doctor Might Order This Test

Your doctor may order ALT testing to monitor liver function, diagnose liver diseases, or check for signs of liver damage after exposure to toxins, infections, or medications.

Common Conditions Linked to ALT Levels

Elevated ALT levels often appear with liver-related issues such as viral hepatitis, alcohol abuse, non-alcoholic fatty liver disease, or certain medications that strain the liver.

What Normal ALT Levels Mean

While reference ranges vary by lab, normal ALT levels indicate healthy liver function. Persistently high or low levels may require further evaluation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

ALT (Liver Enzyme)

Frequently asked questions

How often will I need this test?
ALT testing frequency depends on your health status. Your doctor may order it once to diagnose a problem or regularly if you have ongoing liver concerns, chronic conditions, or take medications that affect the liver.
What causes ALT levels to rise?
ALT levels can rise due to liver damage from infections (like hepatitis), alcohol use, fatty liver disease, certain medications, or metabolic conditions. Other rare causes may include heart failure or muscle disorders.
Can ALT levels drop below normal?
Yes, ALT levels can be low, which may suggest liver cell loss (cirrhosis), severe liver disease, or certain genetic conditions. However, low ALT alone is less common and usually requires further investigation.
  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 16, 2026. · Read our editorial policy