ALTAlanine aminotransferase · SGPT
A liver enzyme that leaks into the blood when liver cells are stressed.
Alanine aminotransferase is an enzyme found mostly inside liver cells. When those cells are damaged or inflamed, ALT leaks into the blood, so the level in a blood test is a marker of liver cell injury rather than of how well the liver is working.
That distinction matters. Liver function is better judged by albumin, clotting time and bilirubin; ALT tells you something is irritating the liver, not whether it is failing. The two can diverge in both directions.
It is usually read alongside AST, another transaminase found in liver and muscle. The ratio between them is informative: alcohol related liver disease characteristically raises AST more than ALT, while fatty liver disease more often raises ALT.
By far the most common cause of a mildly raised ALT in a general population is metabolic dysfunction associated fatty liver, which travels with insulin resistance, central obesity and metabolic syndrome. Alcohol, some medications including certain statins and paracetamol in overdose, viral hepatitis and coeliac disease account for most of the rest.
Exercise is a frequent innocent explanation. Hard or unaccustomed training, particularly eccentric work, raises transaminases from muscle, so a blood test taken a few days after a heavy session can look alarming without anything being wrong with the liver.
That is why a single mildly raised result is usually repeated after a few weeks of no alcohol and no unusual training before anyone investigates further.
In practice, treat a persistently raised ALT as a prompt to look honestly at alcohol and at waist circumference, since fatty liver improves substantially with weight loss and exercise, and to see a GP rather than to buy a liver support supplement.
Where your own result would sit
Most people reading this page are holding a blood-test report with this marker on it, and the question they arrived with is whether their number is normal. A reference interval says where most results from a healthy population fall; a guideline threshold is where a clinical body draws a line for a decision. Neither is a target, and a result on the wrong side of one is not a diagnosis: the same number can be unremarkable in one person and worth looking into in another, which is why the clinician who ordered the test reads it against your history rather than against a list.
ALT has no published interval on this page yet. We hold one, and the dashboard draws it beside a reader’s own result, but it has not been read back against the laboratory’s own page since it was collected. A figure printed beside somebody’s blood result has to have been seen at its source, not remembered, so this one waits.
On your own blood test?
ALT is one of the markers FitTools can read from an uploaded blood-test report. You confirm every value before anything is saved, and your results are explained together in one place.