Rusavy and colleagues recently endeavoured to dissect out the metabolic effects of insulin in patients with severe sepsis, in the setting of normoglycaemia. Twenty stable patients were studied 3–7 days after admission using a euglycaemic clamp at two supraphysiological insulin levels. Increased doses of exogenous insulin caused preferential use of glucose as a metabolic substrate, while total energy expenditure remained constant. Consequently, hyperinsulinaemia reduced tissue oxygen demand and catabolism of protein in patients with sepsis; the benefits of these effects are not proven. The effects of insulin at different time points in sepsis were not examined.