A nurse is providing teaching to a client who has a new diagnosis of type I diabetes mellitus about administering NPH insulin and regular insulin together in one injection. Which of the following instructions should the nurse include?

A. Draw up regular insulin prior to NPH insulin. This is the correct technique when mixing short-acting (regular) and intermediate-acting (NPH) insulins in the same syringe. Drawing up regular insulin first prevents contamination of the clear insulin vial with the cloudy NPH, which could alter the action of the regular insulin. B. Roll the syringe gently to ensure mixture of the insulins. Insulin should be mixed in the vial before drawing it into the syringe—not after. NPH insulin should be gently rolled between the hands to mix it, but the syringe itself should not be rolled after drawing both insulins, as this can introduce bubbles and affect dosing accuracy. C. Inject into the vastus lateralis. The preferred sites for subcutaneous insulin administration are areas with sufficient subcutaneous tissue, such as the abdomen, upper outer arms, thighs, or buttocks. The vastus lateralis is more commonly used for intramuscular injections, such as vaccines. D. Use a 15° angle for the injection. A 15° angle is appropriate for intradermal injections, not subcutaneous insulin injections. For insulin, the correct angle is typically 45° or 90°, depending on the client’s body habitus and needle length, to ensure proper subcutaneous delivery.