Knowing When Insulin has Gone Bad

Kelsey Bonilla Health Guide
  • I’m wondering if anyone has had the same ponderings regarding insulin potency or effectiveness.  One of the mysterious things, for me, has always been whether the insulin vial I’m carrying around is still good or not.  We all know that insulin shouldn’t be left in the heat less it become ineffective or “bad.”  But, what about insulin that’s been kept at room temperature for several weeks? 


    Since I’ve been eating a Paleo diet and therefore needing very little insulin, this question is plaguing me more often.  I’m not even using half a vial of Humalog before it’s been out of the refrigerator for 4 weeks, which leaves me in the quandary of either tossing out insulin that’s actually still good or risk using insulin that’s lost some of its potency.   I wish there was a test for insulin effectiveness (I suppose we could devise one based on our correction bolus ratio??).

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    When I think to do it, I’ll write the date I started using a new vial, on the bottom of it.  This at least addresses the, “How long have I been using this insulin?” question.  But, when I forget that step, I have to ponder that question along with the effectiveness issue.  This occurred just last week.  The vial of insulin was over halfway empty which led me to believe I’d been using it for well over a month, probably over 6 weeks.  Oops.  But, I hadn’t been noticing any unexplained high blood sugars which are typically the catalyst for me suspecting the insulin has gone bad.


    I decided to err on the side of throwing out potentially still useable insulin and started a new vial.  Within the next day or so, I noticed that I didn’t seem to need as much insulin and concluded that the new vial was more potent that the old one.  Funny, I didn’t realize the insulin wasn’t good until I used insulin that was! 


    Does anyone have any tricks for knowing when it’s time to toss a vial of insulin?

Published On: March 16, 2013