When Good Insulin Goes Bad ( Diabetes )
It is not always easy to tell if your insulin has lost its potency, but you should make a habit of closely inspecting your insulin vial, pen, or delivery device every time you use it. First inspect the insulin for any changes in appearance. Is it discolored? Are there any large particles present in the liquid? Are there salt- or glucose-like crystals on the shoulder of the vial? Has your regular, insulin aspart, or insulin lispro that is supposed to be clear become cloudy? If any of these visible changes occur, you should discard the insulin.
Other changes, however, may not be observable with the naked eye. Always be alert for any indication that your insulin may not be working well (such as high blood glucose levels), especially when there are no other explanations. To minimize this possibility, date your vial when you begin using it, store it properly, and discard it after a month, or as recommended by the manufacturer. Some insulin pens or other delivery devices should be discarded sooner, some as early as seven to 14 days.