ALT (GPT)

What is ALT (GPT)?

ALT is a liver enzyme that leaks into your blood when your liver cells are under strain. A little is normal; more of it is like a gentle 'warning light' for your liver. A calm value points to a liver doing its work smoothly: important for your metabolism and your energy.

Clinical frame

ALT (GPT) is a relatively liver-specific enzyme that can rise with hepatocellular injury and metabolic fatty liver. A raised ALT is associated with hepatic steatosis, insulin resistance and metabolic dysregulation ^[2].

An important limitation is that a normal ALT does not rule out fatty liver. A considerable proportion of patients with fatty liver have normal ALT values, and the level of ALT insufficiently reflects the severity of steatosis, inflammation or fibrosis ^[1].

ALT is therefore mainly a supplementary marker and must be interpreted together with other liver values, metabolic parameters and risk scores ^[3].

What moves this value?

Fat build-up in the liver, alcohol, excess weight and sometimes a recent intense workout can raise the value.

Less alcohol and sugar, more movement and weight loss often bring this down gradually. Discuss a persistently high value with your doctor.

References

1. Ma, X. et al. Proportion of NAFLD patients with normal ALT value in overall NAFLD patients: a systematic review and meta-analysis. BMC Gastroenterol 20, 10 (2020). doi.org/10.1186/s12876-020-1165-z
2. Maximos, M. et al. The Role of Liver Fat and Insulin Resistance as Determinants of Plasma Aminotransferase Elevation in Nonalcoholic Fatty Liver Disease. Hepatology 61, 153–160 (2015). doi.org/10.1002/hep.27395
3. American Diabetes Association Professional Practice Committee for Diabetes. Comprehensive Medical Evaluation and Assessment of Comorbidities: Standards of Care in Diabetes—2026. Diabetes Care 49, S61–S88 (2026). doi.org/10.2337/dc26-S004