What is the first step when mixing NPH and regular insulin in the same syringe?

In the process of mixing NPH (intermediate-acting) and regular (short-acting) insulin in the same syringe, the correct first step is to inject air into the NPH insulin vial. This step is essential because each insulin vial is under vacuum, and injecting air into the vial before drawing the insulin helps equalize the pressure.

By injecting air into the NPH vial first, you ensure that you can draw an accurate dose of this intermediate-acting insulin without creating suction that could impede the flow of insulin into the syringe. Proper order and handling while mixing these two different types of insulin are critical for ensuring the correct therapeutic effect and maintaining safe practices.

Subsequently, after injecting air into the NPH vial, you would inject air into the regular insulin vial and then proceed to draw the regular insulin first, followed by the NPH, as the order of drawing insulin types matters to prevent contamination of the regular insulin with NPH.