I've been carrying insulin on planes since 1993 with never an issue. I'm not a physician, but was told by both my endocrinologist and a pharmacist friend that insulin doesn't technically need to be kept refrigerated full time. In face it comes in from medical distributors without any refrigeration. It probably can be ok, according to those sources mentioned above, for up to two weeks. After that it can lose some of its potency but comes back when you refrigerate it.