If you don't refrigerate insulin pens the insulin in the insulin pens can lose it's effectiveness and won't work as it should.
Insulin pens should be stored in the refrigerator at temperatures of between 36 F to 46 F.
When unopened insulin pens are kept at those temperatures in the refrigerator they will remain good and effective until the expiration date.
Opened insulin pens can be stored at room temperature for up to 28 days although it should be refrigerated as they too can lose their effectiveness.
Insulin pens should also be kept away from sunlight, extreme heat and other heat sources.
Insulin products contained in vials or cartridges that are supplied by the manufacturer (opened or unopened) may be left unrefrigerated at a temperature between 59°F and 86°F for up to 28 days and continue to work.
When insulin is bad the insulin often looks cloudy, discolored, clumpy, separated, or like it has little strings in it.
In hot climates were refrigeration is not available for insulin, cooling jars, earthenware pitcher or a cool wet cloth around the insulin will help to preserve insulin activity..