AbstractBackground & AimsIt remains unclear whether the respective dose‐response relationships between serum alanine aminotransferase (ALT) and gamma‐glutamyl transferase (GGT) levels and risk of mortality are consistent by age.MethodsWe used sampled cohort data from the National Health Insurance Corporation to conduct a retrospective cohort study. A total of 313 252 participants who received medical health check‐ups from 2002 to 2008 were assessed for risk of death according to serum ALT and GGT levels over an average of 6 years. The hazard ratios (HRs) for mortality were analysed with Cox proportional hazard model.ResultsThe crude mortality rate increased linearly with increasing serum ALT and GGT levels in adults aged <60 years. However, the all‐cause mortality rate showed a J‐shaped relationship with increasing serum ALT levels whereas all‐cause mortality rate showed a linear relationship with increasing serum GGT levels in adults aged ≥60 years. The HR of death showed U‐shaped relationships with increasing serum ALT levels in adults aged ≥60 years. On the contrary, the HR of death from any cause had a linear association with increasing serum GGT levels among all age groups.ConclusionsIn this study, U‐shaped relationship patterns were demonstrated between serum ALT levels and risk for all‐cause mortality in adults aged ≥60 years while serum GGT levels showed a linear relationship with risk for all‐cause death. Very low levels of serum ALT in elderly patients suggest that they are at high risk of mortality.