A nurse is caring for a client who has a prescription for NPH insulin 10 units and regular insulin 15 units subcutaneously. After injecting 10 units of air into the NPH insulin vial, which of the following actions should the nurse take next?

A. Inject 15 units of air into the regular insulin vial. When mixing NPH and regular insulin, air is first injected into both vials without touching the solution. After injecting air into the NPH vial, the next step is to inject air into the regular insulin vial to maintain proper vial pressure before withdrawing the dose. B. Place the cap over the needle. Recapping needles increases the risk of needlestick injuries and is not necessary during the insulin preparation process. The needle should remain uncapped until both insulins are drawn and the injection is ready. C. Withdraw 10 units of NPH insulin. Regular insulin should be drawn first to prevent contamination with NPH insulin. Since NPH is a cloudy suspension and regular insulin is clear, drawing regular insulin first ensures that the short-acting insulin remains unaltered. D. Verify the dosage with another nurse. While verifying high-risk medications like insulin is important, the appropriate step after injecting air into the NPH vial is to proceed with injecting air into the regular insulin vial before withdrawing any insulin.