A nurse is teaching a newly licensed nurse about insulin storage. Which of the following statements by the newly licensed nurse indicates an understanding of the teaching?

A. Once a vial of insulin is opened, it can safely be stored at room temperature (generally 15–29°C / 59–86°F) for up to 28 days, depending on the manufacturer’s guidelines. Storing in-use insulin at room temperature prevents the discomfort of injecting cold insulin and does not compromise medication effectiveness within the recommended time frame. This demonstrates appropriate understanding of safe insulin storage. B. Insulin should never be frozen, as freezing damages the protein structure, making the medication ineffective and unsafe to administer. If insulin accidentally freezes, it must be discarded. The correct practice is to store unopened vials in the refrigerator, not the freezer, until ready for use. C. There is no requirement to return unopened insulin after 1 month on the unit. Unopened insulin vials are stable when refrigerated and can be stored until their manufacturer’s expiration date. Returning vials after only 1 month would lead to unnecessary waste and is not consistent with medication management guidelines. D. Insulin is not discarded based on the number of doses withdrawn. Instead, discard recommendations are based on time after opening, generally 28 days for most insulins. The vial remains usable as long as it is within this timeframe, properly stored, and free of contamination or cloudiness (unless it is an insulin type that is normally cloudy).