A client with type 2 diabetes mellitus is feeling diaphoretic, anxious, and hungry, unable to swallow or follow commands. The nurse noticed these symptoms occurred 45 minutes after an insulin injection. The nurse suspects the client is experiencing insulin toxicity. Which of the following medication should the nurse have available for this client?

A. Regular insulin – This is incorrect. Regular insulin would exacerbate hypoglycemia since it lowers blood glucose levels. Administering insulin in this scenario would worsen the client's condition. B. Diphenhydramine (Benadryl) – This is incorrect. Diphenhydramine is an antihistamine and has no role in treating hypoglycemia or insulin toxicity. C. Metformin (Glucophage) – This is incorrect. Metformin is an oral hypoglycemic agent and is not suitable for immediate treatment of insulin-induced hypoglycemia. D. Glucagon (GlucaGen) – This is correct. Glucagon raises blood glucose by promoting glycogen breakdown in the liver and is the treatment of choice for severe hypoglycemia in clients unable to swallow or follow commands.