Patient’s clinical course in the present case. On day 26, before diabetic ketoacidosis, insulin secretion is preserved, based on serum C-peptide (CPR) 0.5 nmol/L and fasting plasma glucose (FPG) 5.1 mmol/L. At the time of admission, FPG was highly elevated, and insulin secretion had declined, but not become exhausted (day 1 CPR 0.1 nmol/L and FPG 13.0 mmol/L). Continuous insulin replacement was required to manage plasma glucose. The patient’s insulin secretion declined steadily, leading to exhaustion 9 days after the ketoacidosis event. Her insulin secretion had not recovered by 5 months later.