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. Use a 15° angle for the injection: Subcutaneous insulin injections should be administered at a 90° angle for most adults and children with adequate subcutaneous tissue. A 15° angle is too shallow and may result in intradermal administration, affecting absorption. B. Roll the syringe gently to ensure mixture of the insulins: Only the NPH insulin vial should be gently rolled between the hands to resuspend the cloudy insulin. Regular insulin is clear and should not be shaken, and the mixture occurs in the syringe after drawing up each insulin in the correct sequence. C. Draw up regular insulin prior to NPH insulin: Drawing up regular (clear) insulin before NPH (cloudy) insulin prevents contamination of the short-acting insulin with intermediate-acting insulin, maintaining proper pharmacologic action and preventing altered onset or peak times. D. Inject into the vastus lateralis: The preferred sites for subcutaneous insulin injections are the abdomen, upper arm, or anterior thigh. The vastus lateralis can be used in infants but is not the standard site for older children or adults.