A nurse is preparing to mix a dose of NPH insulin and regular insulin into a single syringe. Which of the following actions should the nurse take first?

A. Withdraw dose of regular insulin: Withdrawing the regular insulin dose is performed after the air has been injected into both vials and the NPH insulin has been drawn up if using the “clear before cloudy” technique. Doing this first would risk disrupting the proper sequence and potentially contaminating the insulin. B. Inject air into the vial of regular insulin: Air must be injected into the regular insulin vial before withdrawing the medication, but this step is performed after first injecting air into the NPH vial according to the standard procedure for mixing insulins. Starting with the regular insulin vial would not follow the recommended order. C. Inject air into the vial of NPH insulin: Injecting air into the NPH insulin vial first is the initial step when preparing a mixed insulin dose. This step equalizes pressure inside the vial, allowing for easier withdrawal later, and follows the correct sequence of “air into cloudy first, then clear,” which prevents contamination of the regular insulin. D. Withdraw dose of NPH insulin: Withdrawing NPH insulin is done after the regular insulin has been drawn into the syringe to maintain the correct “clear before cloudy” technique. Doing this first could result in accidental mixing or contamination of the regular insulin.