Insulin is very sensitive to sunlight, indoor lights, and to extremely hot or cold temperatures.
Insulin is not OK to use if exposed to very hot or cold weather. The three drug manufacturers of insulin in the United States say UNOPENED insulin is best stored inside the fridge [2° to 8°Celcius (36° to 46°Fahrenheit)]. UNOPENED insulin stored in the refrigerator is good until the expiration date printed on the insulin box. The expiration date will usually be 1 year from the date of purchase but you have to check the box to find out
Once open there are different storage needs for insulin. What does OPEN mean? This does NOT mean removed from the box. OPEN means the insulin cap is removed and the rubber stopper was punctured.
Vials and pens have different needs for storage. These differences can lead to confusion. Therefore, it is very important for you to become familiar with the recommendations for the insulin product that you use.
Vial: Once the vial is punctured, it is OPEN. Once you stick a needle in the vial, it is OPEN. OPEN vials can be stored in the fridge or at CONTROLLED room temperature. Regardless of where it is stored, OPEN insulin will only last 28 days before it must be thrown away. Insulin kept in the fridge should be removed and allowed to reach room temperature before injection.
PEN: Once used for the first time, insulin pens should not be stored in the fridge. Instead, they should be stored at CONTROLLED room temperature. The number of days you can use the pen will depend on which pen you use. Talk to your doctor or pharmacist. Pens last 7-28 days if stored at CONTROLLED room temperature. The number of days depends on which pen you use.