What is the first action a nurse should take when mixing regular insulin and NPH insulin?

The first action a nurse should take when mixing regular insulin and NPH insulin is to inject air into the NPH vial before drawing up the insulin. By injecting air into the NPH vial first, the nurse ensures that the NPH insulin can flow freely when it is later drawn up. This technique helps prevent the NPH vial from creating a vacuum which could make it difficult to withdraw the proper amount of insulin.

Additionally, this practice adheres to the correct order of mixing insulins, where the long-acting (NPH) insulin is handled first. Proper technique minimizes the risk of contamination and ensures the accuracy of insulin doses, which is vital for patient safety and effective diabetes management.