What Is ALT in a Blood Test? Normal Range & What High Levels Mean
Also known as: Alanine aminotransferase, SGPT, ALT blood test
ALT (alanine aminotransferase) is an enzyme found mainly in your liver cells. When liver cells are damaged, ALT leaks into the bloodstream, so a blood test measuring ALT is used to check for liver stress or injury. A normal adult ALT level is roughly 7–56 units per liter (U/L); higher levels often point to liver inflammation, while very low levels are rarely a concern.
ALT normal range
| Category | Range (U/L) |
|---|---|
| Adult men | 7–55 U/LReference ranges vary by lab |
| Adult women | 7–45 U/L |
| Commonly cited normal | 7–56 U/L |
| Mildly elevated | 56–150 U/LOften fatty liver, alcohol, medications |
| Markedly elevated | >150 U/LWarrants prompt medical evaluation |
Reference ranges vary by laboratory. Use the range printed on your own report as the definitive comparison.
What high ALT can mean
- Non-alcoholic fatty liver disease (the most common cause of mildly high ALT)
- Alcohol-related liver injury
- Viral hepatitis (A, B, or C)
- Certain medications and supplements (e.g. statins, acetaminophen, some herbals)
- Recent intense exercise or muscle injury (ALT is also present in muscle)
What low ALT can mean
- Low ALT is usually normal and not a cause for concern
- Occasionally associated with vitamin B6 deficiency
What to do about an abnormal result
- Compare your value to the reference range printed on your own report — lab ranges differ.
- Mildly elevated ALT is common and often reversible with weight loss, reduced alcohol, and reviewing medications.
- Ask your doctor whether a repeat test, a full liver panel, or imaging is warranted.
- Don't self-diagnose from a single number — ALT is interpreted alongside AST, ALP, and bilirubin.
Understand your own results
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Frequently asked questions
What is a dangerously high ALT level?
ALT levels above roughly 10 times the upper limit of normal (over ~500 U/L) can indicate acute liver injury and should be evaluated by a doctor promptly. However, context matters — your physician interprets ALT alongside other liver markers and your symptoms.
Can exercise raise ALT?
Yes. Strenuous exercise and muscle injury can transiently raise ALT because the enzyme is also present in muscle tissue. Many labs suggest avoiding heavy exercise for 24–48 hours before testing.
Does high ALT always mean liver disease?
No. Mildly elevated ALT is common and can be caused by fatty liver, medications, alcohol, or even recent exercise. A single mildly high value is usually rechecked before any diagnosis.
Related biomarkers
Medically reviewed by Antonieta Rueda, MD and Ayham Shneker, MD · Last reviewed July 6, 2026
This article is for informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or your lab results.