Diabetes ketoacidosis (DKA) and diabetes ketosis (DK) are severe complications of diabetes mellitus (DM).A retrospective study on 54 dogs with diabetes keto(acido)sis (DK(A)) was performed. The patients weremostly middle-aged to old female intact dogs with a history of polyuria/ polydipsia, lethargy, anorexia,vomiting, weight loss, diarrhea, hematuria, pollakisuria or shock. In 57.4% of the dogs, a previous diagnosisof DM was not established. Diabetes keto(acido)sis was frequently associated with a concurrent disease suchas pancreatitis (22.2%), hypercortisolism (7.4%), neoplasia (24%), infections (24%), renal failure (13%) orheart failure (7.4%). To evaluate the patient and to search for a concurrent disease, a complete blood countand serum biochemistry, blood gas analysis, urinalysis, urine culture, thoracic radiographs and/or abdominalultrasound were performed. The treatment of the DK(A) depended on the concurrent disease, the blood valuesand the symptoms of the dog. The prognosis was poor, since 48% of the dogs died or were euthanized within2 weeks after diagnosis. Relapse occurred in 5 dogs (9.3%), mostly within 6 months.