Final answer:
When mixing insulin, the client should gently roll the vial instead of shaking it vigorously. They should also avoid mixing regular insulin with long-acting insulin.
Step-by-step explanation:
When mixing insulin, the client should be instructed to roll the vial gently instead of shaking it vigorously. Shaking the vial can create air bubbles, which can affect the accuracy of the insulin dose. It is important to gently roll the vial between the palms to ensure proper mixing without introducing any air bubbles. Furthermore, it is crucial to avoid mixing regular insulin with long-acting insulin in the same syringe, as it can alter the action of the insulin and lead to unpredictable blood sugar levels.