Abstract. Lommi J, Koskinen P, Näveri M, Härkönen M, Kupari M (Helsinki University Central Hospital, Helsinki, Finland). Heart failure ketosis. J Intern Med 1997; 242: 231-8.Objective. To assess whether blood ketone bodies are increased in congestive heart failure (CHF). Methods. Thirteen patients with CHF and 11 cardiac patients without CHF took part in the study. Blood acetoacetate and b-hydroxybutyrate levels and the pertinent metabolic and hormonal milieu were measured during 20 h fast and after 2 h glucose infusion. Results. The averaged blood ketone body and free fatty acid levels were significantly higher during the fast and also remained higher after glucose infusion in patients with CHF than in the control group. The areas under ketone body concentration time curve over the last 8 h of the fast were 3522 Ϯ 662 mol L Ϫ1 h Ϫ1 (SE) and 1789 Ϯ 192 mol L Ϫ1 h Ϫ1 in patients with and without CHF, respectively (P = 0.022). Circulating noradrenaline and growth hormone were higher but glucagon lower in patients with CHF than in the controls (P Ͻ 0.05 for all differences) whereas the glucose and insulin concentrations were comparable in the study groups. At the time of peak ketonaemia, the glucagon-to-insulin ratio was lower in patients with CHF than in patients without CHF (P ϭ 0.04). Conclusions. These data suggest that severe CHF is a ketosis-prone state. Augmented supply of free fatty acids for ketogenesis due to increased stress hormone-related lipolysis is one likely mechanism.