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?

The correct answer is D: Glucagon (GlucaGen). In cases of insulin toxicity, glucagon is indicated to counteract the effects of excess insulin by increasing blood glucose levels. Glucagon stimulates the liver to release stored glucose into the bloodstream, helping to raise blood sugar levels rapidly. This is crucial in preventing severe hypoglycemia and reversing the symptoms observed in the client. Regular insulin (choice A) is not appropriate as it would further lower blood sugar levels. Diphenhydramine (choice B) is an antihistamine used for allergic reactions, not insulin toxicity. Metformin (choice C) is used for managing type 2 diabetes and does not directly address insulin toxicity.