When drawing up two types of insulin for a patient, which sequence is correct?

• A. Draw up regular insulin before drawing up NPH insulin.
• B. Draw up the insulins in two separate syringes.
• C. Draw air into regular, withdraw 10 U, then draw air into NPH and withdraw 35 U.
• D. Inject 35 U air into the NPH, inject 10 U air into regular, withdraw 10 U regular, and withdraw 35 U NPH.

Answer: (D)

Mixing insulins in one syringe requires a technique that prevents contamination and ensures the correct order and dosage. The correct approach is to prepare the two vials by first injecting air into the intermediate-acting insulin (NPH) vial, then injecting air into the regular (short-acting) insulin vial, followed by withdrawing the regular insulin dose first and then the NPH dose. This exact sequence—air into NPH, air into Regular, withdraw Regular (10 units), then withdraw NPH (35 units)—keeps the regular insulin from becoming contaminated with NPH and ensures the doses go into the syringe in the proper order.

Why the other patterns aren’t ideal: simply drawing up regular before NPH without the accompanying air-injection steps can risk contamination and incorrect withdrawal, and using two separate syringes adds handling steps and potential for dosing errors. The specified air-injection order and withdrawal order in this sequence align with correct mixing technique and dose accuracy.