ALT, alanine aminotransferase, is an enzyme concentrated inside liver cells, where it takes part in amino acid metabolism. What the blood test measures is the amount that has leaked out of those cells, so it is read as a marker of liver cell integrity rather than of overall liver function. Smaller amounts come from muscle and kidney tissue.
No readings for this marker yet.
Raised ALT most often points to irritation or injury of liver cells: fatty liver, alcohol, viral hepatitis, or a reaction to a medicine or supplement are among the usual explanations, and mild, transient elevations are common. Larger rises tend to accompany more acute liver insults. Low results carry little clinical weight and are occasionally linked to vitamin B6 deficiency. A single out-of-range value is a reason to repeat the test and bring it to a doctor, not a finding on its own.
Strenuous exercise in the days before the draw, recent alcohol, body weight, and many common drugs — paracetamol, ibuprofen, diclofenac and other anti-inflammatories among them — can shift the result, as can a haemolysed sample. ALT is rarely interpreted alone: it is read next to AST, GGT, alkaline phosphatase, total and direct bilirubin, albumin and total protein, and the pattern across them says more than any single enzyme.
Reference ranges are general adult values and depend on lab, assay, age and sex. For orientation, not diagnosis — discuss results with your doctor.