For how long can I use a vial of insulin?

The expiration date on insulin packaging is for unopened, refrigerated vials, disposable pens, or pen cartridges. Once opened, most vials of insulin last for 28 days, even if refrigerated, but many pens and pen cartridges are good for only 7, 10, or 14 days (and should not be refrigerated).Learn more about insulin here.