A nurse is teaching a client who has diabetes mellitus and receives 25 units of NPH insulin every morning if her blood glucose level is above 200 mg/dL. Which of the following information should the nurse include?

A. Discard the NPH solution if it appears cloudy: NPH insulin is naturally cloudy and should not be discarded because of its appearance. Cloudiness is a characteristic of NPH insulin, which is an intermediate-acting insulin, and it should be gently rolled before use. B. Shake the insulin vigorously before loading the syringe: NPH insulin should not be shaken vigorously, as this can cause air bubbles and affect the proper mixing of the insulin. Instead, it should be rolled gently between the palms of the hands to mix it properly. C. Freeze unopened insulin vials: Insulin should never be frozen. Freezing can damage the insulin, rendering it ineffective. Unopened insulin vials should be stored in the refrigerator, not in the freezer, and should not be used if they have been frozen. D. Expect the NPH insulin to peak in 6 to 14 hr: NPH insulin is an intermediate-acting insulin, and its peak action typically occurs between 6 and 14 hours after administration. This means the insulin will have its greatest effect during this time window, which is important for managing blood glucose levels.