A 22-year-old woman with type 1 diabetes is brought to the emergency department with vomiting and abdominal pain. She has been feeling unwell for 2 days and has missed several insulin doses. On examination she is drowsy, dehydrated, with Kussmaul respirations and a ketotic breath smell. Capillary blood glucose is 27 mmol/L and venous blood gas shows pH 7.12. What is the most likely diagnosis?