Can Insulin Be Stored Outside Fridge? by Pooja Shete on March 1, 2021 at 12:29 AM A new study indicates that insulin may be more heat-stable during 28 days of use than current labeling suggests. Instructions on insulin vials or pens state that they can be stored unopened at temperatures of 2° to 8° C (35.6° to 46.4° F). However, once the seal is punctured and during 28 days of use, the label states that the insulin should be stored at temperatures of 25° to 30° C (77° to 86° F). In many parts of the developed world as well as in many resource-poor settings, temperatures are higher than that. This study was conducted under laboratory conditions similar to those of a refugee camp in northern Kenya, where temperatures typically fluctuate between 25° C (77° F) at night and 37° C (98.6° F) during the day.