The authors describe a case of a patient admitted to the emergency department with diabetic ketoacidosis. Although there were no symptoms attributable to the cardiovascular system, lab tests revealed elevated troponin I and natriuretic peptides, coupled with repolarization abnormalities on the ECG. The transthoracic echocardiogram (TTE) showed a non-dilated left ventricle with severe left ventricular systolic dysfunction due to diffuse hypokinesia, and a concomitant diagnosis of profile L heart failure was proposed. Etiologic investigation was negative, and when a new TTE was performed seven days after the first, left ventricular function was normal. Although rarely considered, metabolic and electrolyte disorders, especially diabetic ketoacidosis, can be a cause of left ventricular systolic dysfunction, and should be considered in the differential diagnosis. This is another way diabetes can have an impact on the cardiovascular system. Published by Elsevier Espana, S.L.U. on behalf of Sociedade Portuguesa de Cardiologia.