The aims of this study were to investigate management routines of diabetic ketoacidosis (DKA) in adult patients in departments of internal medicine in Denmark and to relate current routines of treatment to available evidence. A questionnaire requesting information on management routines of DKA was sent to all departments of internal medicine in Denmark responsible of managing DKA. Fifty-nine departments (88%) returned the questionnaire and/or a copy of their management protocol. At 19 departments (32%), all patients with DKA were managed in an intensive care unit (ICU). Twenty-four different insulin regimens and 21 fluid protocols were identified. Routines of insulin therapy varied in terms of doses and routes of administration. Fifty-eight departments (97%) used isotonic saline for hydration. Potassium supplements were administered as a separate infusion of either isotonic potassium-sodium-chloride (83%) or isotonic potassium-chloride (10%). Recommended volumes to be administered during the first 8h of treatment varied significantly (median 4800ml, range 3750-7700ml). Use of bicarbonate was endorsed by 80%. This study shows significant variations in management routines of DKA in Denmark. In many cases, the treatment routines employed are not supported by evidence from clinical trials. We recommend implementation of national and/or European guidelines for management of DKA in adult patients.