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January 10, 2003


Question from Johannesburg, South Africa:

We generally don't have any problems with NovoRapid and Protaphane (NPH) in terms of keeping them at room temperature for up to a month, but recently, it seems that three week old insulin did suffer from reduced effectiveness after a long hot journey in a car even though the insulin was in the manufacturer's insulating bag. Are there any specific test findings or recommendations regarding these two insulins and temperature/age?


There are no specific recommendations other than to keep them cool as long as possible to maximize their shelf life. The thing you do not know is how the insulin was handled during shipping. The hot car will cause the insulin to break down. The same can be said for direct sunlight or freezing cold.

There is a selection of commercially available products that hold the insulin and keep it insulated from outside temperatures. You may want to contact a medical supply business to see these. There is no test you can use to determine the insulin’s potency other than to use it and having a back-up supply is always a good idea.

Additional comments from Dr. Stuart Brink:

Use common sense. If it is very cold or very hot, then appropriate insulating material should be used. Cardboard packages do not have much insulation power. In hot weather, then some cold packs usually do quite nicely.

There is not much difference with any of the major brand insulins with regard to temperature stability, although some anecdotal information about human synthetic human and analog insulins being a bit more temperature labile than the older animal-source insulins.


[Editor’s comment: See Carrying Cases.