ALT Blood Test (Alanine Aminotransferase, SGPT)

This test measures the activity of alanine aminotransferase (ALT) in your blood serum. ALT is found in highest concentration in the liver, and Quest notes that significant elevations occur only in liver disease. Comparing ALT with AST helps show whether a raised AST comes from the liver or from another tissue such as heart or muscle.

People who had a high ALT on a previous test and want to re-check it; people whose clinician wants ALT monitored while they take a medicine that can affect the liver; and people at higher risk of liver problems, such as those with a family history of liver disease, heavy alcohol use, obesity, diabetes, or hepatitis or exposure to it. If you have symptoms of liver disease, see a clinician; a full panel is usually more useful than ALT alone.

Any time of day; no fasting is needed for ALT. For a re-check, test after the interval your clinician suggests, so you are comparing like with like. Because intense exercise and some medicines and supplements can shift ALT, try to test under your usual routine rather than right after an unusually hard workout.

A result within the lab's reference range means no sign of liver-cell injury on this marker. A high ALT can come from hepatitis (viral or alcohol-related), fatty liver disease, certain medicines (such as some cholesterol or pain medicines), cirrhosis, reduced blood flow to the liver, or toxins; it can also be nudged up by intense exercise, weight and some supplements. A mildly high value is common and is often repeated before anything else is done; a persistently high ALT is usually followed by tests for viral hepatitis, iron overload and other causes, guided by your clinician. A low ALT is uncommon and is rarely a concern, though it can occur with vitamin B6 deficiency or chronic kidney disease. Reference ranges differ by age and sex. JustLabs results are informational; review them with a clinician.