Which insulins should never be mixed?

The correct answer highlights the importance of understanding the unique properties of different insulin formulations. Insulin U-500, which is a concentrated form of regular insulin, is designed to be more potent and requires careful handling. Mixing it with long-acting insulins can lead to unpredictable absorption patterns and potential overdosing or underdosing. Each insulin type has its specific action profile, and when mixed, it may result in a change in the intended pharmacokinetics, ultimately complicating treatment and increasing the risk of adverse effects.

In contrast, the other combinations listed, although they might have concerns regarding mixing, typically do not present the same level of risk as mixing U-500 with long-acting insulins. For example, mixing regular insulin with NPH is commonly practiced, as NPH serves as a medium-acting insulin that can complement the short-acting nature of regular insulin. Understanding these distinctions is crucial for safe and effective insulin management in diabetes care.