Test Your Knowledge Answer #417

 

This pattern of hyperglycemia is classic for a situation in which a specific insulin component of the regimen has become ineffective. In this case, hyperglycemia occurs after lunch and before dinner but only on the days in which the insulin pen is being used. There are several possible reasons for this sudden onset of ineffective insulin action. First, the patient indicates that the ambient temperature was high and that he left his insulin pen in his truck—very likely, the insulin lost potency. Another possibility is that the pen is not working correctly or that the patient's technique is poor. Prior to this episode, however, the patient used the pen adequately.

 

All insulins should be stored at temperatures between 2.2 °C and 30 °C (36 °F and 86 °F). Any insulin that has been frozen or has been exposed to temperatures above 30 °C (86 °F) should be discarded. Unopened insulin vials and pens should be stored in the refrigerator. After 30 days, patients should discard opened, in-use vials, whether stored in the refrigerator or at room temperature; discard unopened vials that have been stored at room temperature; and discard opened, in-use pens or pen cartridges, which should not be stored in the refrigerator. Insulin glargine is particularly susceptible to loss of effectiveness and should not be used beyond 30 days, whether stored in the refrigerator or at room temperature.

 

A patient's fasting glucose level reflects the adequacy of the insulin glargine dosage and, in this case, the fasting blood glucose levels are very good. The patient's insulin-to-carbohydrate ratio also appears to be correct because it works at all other meals, including weekend lunch. Finally, poor carbohydrate counting skills would not explain the sudden, selective deterioration in post-lunch and pre-dinner blood glucose control.

 

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