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Alanine Aminotransferase (ALT) in Serum/Plasma

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

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

Quick summary

["ALT helps doctors check for liver problems, including inflammation or injury."]

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

Key facts at a glance

LOINC
57994-6
Short code
Leucine/Alanine DBS
Synonyms
Leucine/Alanine DBS
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

Why ALT Matters for Your Health

ALT is a key marker for liver function. High levels may suggest liver damage, such as from hepatitis, alcohol use, or other conditions that stress the liver. Low levels are less commonly significant unless part of a broader evaluation.

How ALT Levels Are Interpreted

Results are compared to a baseline or reference range provided by your healthcare provider. While reference ranges vary by lab, elevated ALT often signals liver issues, but it’s not the only test needed for diagnosis.

Common Causes of ALT Elevation

Elevated ALT can result from viral hepatitis (e.g., hepatitis B or C), alcohol consumption, fatty liver disease, certain medications, or metabolic conditions like diabetes. It may also appear after liver injury or certain infections.

What to Expect During the Test

This test involves drawing blood from a vein in your arm. You may feel slight discomfort, but it usually takes a few minutes. No special preparation is needed unless instructed otherwise by your doctor.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: ALT in Diagnosis and Monitoring

Short name

ALT Test

Frequently asked questions

What does an elevated ALT level mean?
An elevated ALT level often signals liver problems, but it’s not definitive on its own. Your doctor may order additional tests (e.g., liver function tests, imaging, or viral hepatitis panels) to identify the cause. For example, high ALT with low bilirubin might suggest early liver damage, while persistent elevation could indicate chronic conditions like cirrhosis.
Can ALT levels be affected by diet or medications?
Yes, certain foods (e.g., fatty foods) or medications (e.g., acetaminophen in high doses, certain antibiotics, or statins) can temporarily raise ALT levels. Alcohol use and viral infections are also strong contributors. Always discuss your medications, supplements, or recent dietary changes with your doctor.
How often should ALT be checked?
ALT is typically checked as part of routine liver function tests, especially if you have symptoms like fatigue, jaundice, abdominal pain, or a known risk for liver disease (e.g., hepatitis, obesity, or diabetes). Your doctor may recommend follow-up tests based on your results and health history.
  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