ALT
Alanine aminotransferase (ALT) is an enzyme predominantly found in liver cells (hepatocytes), with small amounts in kidneys and muscle. When liver cells are damaged or inflamed, ALT leaks into the bloodstream. ALT is the most liver-specific of the common liver enzymes, making it the primary marker for hepatocellular injury.
Why it matters: Even mildly raised ALT is associated with non-alcoholic fatty liver disease (NAFLD), which is common worldwide. Persistently raised ALT is associated with greater liver-related risk over time, and ALT is often the first change seen in fatty liver, viral hepatitis, and medication-related liver injury.
May increase with:
May decrease with:
What is ALT?
Alanine aminotransferase (ALT) is an enzyme predominantly found in liver cells (hepatocytes), with small amounts in kidneys and muscle. When liver cells are damaged or inflamed, ALT leaks into the bloodstream. ALT is the most liver-specific of the common liver enzymes, making it the primary marker for hepatocellular injury.
What might a high or low ALT mean?
Even mildly raised ALT is associated with non-alcoholic fatty liver disease (NAFLD), which is common worldwide. Persistently raised ALT is associated with greater liver-related risk over time, and ALT is often the first change seen in fatty liver, viral hepatitis, and medication-related liver injury.
What is the typical reference range for ALT?
The general-population reference range shown here is < 45 U/L. Reference ranges describe the general population and are not a personal target — discuss your results with your physician.
What can affect ALT?
It may be higher with: Non-alcoholic fatty liver disease (NAFLD), Alcohol consumption, Viral hepatitis (B, C), Medications (statins, acetaminophen, NSAIDs), Obesity and insulin resistance, Celiac disease, Intense exercise (transient, mild), Herbal supplements (kava, green tea extract in excess). It may be lower with: Weight loss (5-10% reduces ALT significantly), Reduced alcohol intake, Mediterranean diet, Exercise (both aerobic and resistance), Coffee consumption (2-3 cups/day is hepatoprotective), Treating underlying cause (antivirals for hepatitis), Omega-3 fatty acids, Vitamin E (for NASH — under medical supervision).