[An elderly patient with type 2 diabetes who developed a hyperglycemic emergency and showed a marked decline in insulin secretion, but she was able to be weaned off insulin by alleviating glucose toxicity and adjusting her medication: A case report].

An 82-year-old woman with an impaired consciousness presented to our hospital. She was diagnosed with diabetic ketoacidosis and cellulitis and was admitted to the hospital. Following acute-phase treatment, continuous intravenous insulin infusion was discontinued, and multiple daily injections were initiated on the fourth hospital day (day 4). On day 9, a postprandial test revealed serum C-peptide and blood glucose levels of 0.55 ng/mL and 218 mg/dL, respectively, thus indicating significantly decreased insulin secretion. A subsequent fasting test on day 16 showed serum C-peptide and blood glucose levels of 0.42 ng/mL and 140 mg/dL, respectively, confirming the continued deficiency of insulin secretion. Although discontinuing insulin was anticipated to be difficult based on her low C-peptide levels, a gradual reduction in the insulin dose was planned in preparation for transfer from the hospital to an older adult care facility. After initiating dulaglutide and repaglinide treatment, insulin therapy, which peaked at 23 units/day, was discontinued. The resolution of glucotoxicity and pharmacotherapy, including glucagon-like peptide-1 receptor agonists, may have contributed to the discontinuation of insulin therapy in some patients. The serum C-peptide levels and 24-h urinary C-peptide excretion have been reported to be useful predictors of the need for insulin therapy to achieve optimal glycemic control. Although insulin withdrawal was predicted to be challenging based on previous reports, it was successfully performed in the present case. This case represents a suggestive example that highlights the relevant considerations for evaluating the residual insulin secretory function.