A 64-year-old man with type 2 diabetes had been receiving combination therapy with a sulfonylurea drug and long-acting insulin. He discontinued insulin after a fall 2 weeks prior to consultation, developed abdominal distension of a 1-week duration, and was brought by ambulance. He had mild disturbance of consciousness. Although anti-GAD antibody was negative, the urinary CRP level was decreased to 31.6 mg/day. The HbA1c level was 9.1%, blood glucose level 994 mg/dL, and serum osmotic pressure 391 mOsm. The acetoacetic acid, hydroxybutyric acid, and blood total ketone body levels were markedly elevated. He had a strong ketone odor on his breath. These findings suggested a disease condition resulting from a combination of hyperglycemic hyperosmolar syndrome (HHS) and diabetic ketoacidosis (DKA). On the other hand, the presence of abdominal distension, absence of bowel sounds, and imaging-based evidence of bowel distension led to a diagnosis of paralytic ileus. We report this case because it is unique in that the patient developed HHS, DKA, and paralytic ileus.