A nurse is preparing to administer 5 units of regular insulin and 20 units of NPH insulin to a client who has type 1 diabetes mellitus. Which of the following actions should the nurse take first?

Answer: (A) Inject 20 units of air into the vial of NPH insulin. Rationale: A) Inject 20 units of air into the vial of NPH insulin: Injecting air into the vial of NPH insulin is the first step to prevent creating a vacuum, which could make it difficult to withdraw the insulin later. The nurse must inject the corresponding amount of air for the dose needed, ensuring that the insulin can be withdrawn smoothly and accurately without bubbles, which could affect the dose. B) Inject 5 units of air into the vial of regular insulin: Injecting air into the regular insulin vial is also necessary before withdrawing the insulin, but it should be done after injecting air into the NPH vial. This sequence ensures that no NPH insulin contaminates the regular insulin vial when the nurse withdraws the doses later. C) Withdraw 20 units of NPH insulin from the vial: Withdrawing NPH insulin should be done after air is injected into both vials and after the regular insulin has been drawn up. This sequence prevents the mixing of the two types of insulin and ensures accurate dosing, which is crucial for maintaining the correct blood glucose levels. D) Withdraw 5 units of regular insulin from the vial: Withdrawing regular insulin is critical to do before the NPH insulin to prevent contamination of the regular insulin with NPH, which could alter the onset and peak times of the regular insulin. However, it should follow the steps of injecting air into both vials, starting with the NPH vial.