What is a sign that insulin may be ineffective due to improper storage?

The indication that insulin may be ineffective due to improper storage is when it appears cloudy or has crystals. Insulin should typically be clear and free of any particles or precipitates. When insulin is improperly stored—whether it is exposed to extreme temperatures or is left out of refrigeration for too long—it can degrade, causing changes in its appearance. The formation of a cloudy appearance or visible crystals suggests that the insulin may no longer be effective, posing a risk to the patient who may rely on it for blood glucose control.

In contrast, the other signs are less indicative of ineffectiveness related to storage. Clear and odorless insulin is normal for many types of insulin, signaling that it is likely still viable. A strong odor is not a standard characteristic of insulin and usually does not provide reliable information about its efficacy, while insulin being warm to the touch can suggest that it has been stored improperly, but does not specifically indicate degradation in efficacy like cloudiness or crystal formation does.