Decreased insulin sensitivity precedes the onset of type 2 diabetes mellitus (T2DM). Hepatic energy metabolism is assumed to be impaired in T2DM with reduced insulin sensitivity. However, little is known about changes of ATP content in response to acutely elevated insulin. Therefore utilizing 31P MRS, we quantified ATP content before and after acute hyperinsulinemia. After a hyperinsulinemic clamp test, hepatic γ-ATP concentrations (ATP) were significantly reduced by 18% (p=0.008) in T2DM but not in controls. This study demonstrated that quantitative 31P MRS allows to monitor acute changes in hepatic ATP concentrations in vivo in various metabolic conditions.