A nurse is mixing a short-acting insulin and an intermediate-acting insulin in the same syringe for a client who has diabetes mellitus. Which following actions should the nurse take first?

To mix short-acting and intermediate-acting insulin in the same syringe, the nurse should first inject air into the intermediate-acting insulin vial (A) to prevent vacuum formation. Next, inject air into the short-acting insulin vial (C) to maintain pressure balance. Then, draw the short-acting insulin into the syringe (D) before drawing the intermediate-acting insulin (B) to avoid contamination. This order ensures proper mixing and accurate dosing of the insulins, minimizing the risk of errors. Injecting air first prevents negative pressure, which can make it difficult to withdraw the correct amount of insulin. Therefore, the correct order is A, C, D, B.