The American Diabetes Association offers these guidelines for proper storage of insulin:

• Insulin typically is stored in the refrigerator, but it may be more painful when injected this way. Insulin stored at room temperature will last about a month.
• Don't keep your insulin in extremely hot or extremely cold temperatures.
• Never keep insulin in the car, in direct sunlight or in the freezer.
• Check the bottle's expiration date, and discard any insulin that's expired.
• Inspect the bottle before inserting the syringe to make sure the insulin looks as it should.
• Don't use insulin that has formed any crystals or clumps.

-- Diana Kohnle