Nearly every diabetes supply I own comes with an expiration date. Insulin vials, pods, ketones testing strips, and Dexcom sensor/transmitters are among the items that I’m always closely monitoring to ensure they’re still fresh and usable, but test strips? They’re basically the last thing that I worry about.

So I was curious when I recently noticed that my current test strip vial has an expiration date of 12/31/19. Would these strips still measure my blood sugar accurately, or was the New Year’s Eve expiration hard and fast?

I wanted to find out.

My experiment design was rudimentary: I’d simply continue to use the 12/31/19 test strips until the vial was empty. I’d check any blood sugar results that I was unsure about against my Dexcom readings, and in cases that I deemed necessary, I’d use test strips with a far-off expiration (July 2020) to see how they matched up with the expired strips.

To my slight surprise, though it’s only been about a week since the old strips expired, it doesn’t seem to affect things much at all. They’re just as accurate as newer strips and my Dexcom.

In fact, in many cases, the old strips were only off (according to my measurements) by no more than 9 points. Not bad. I’ve had a wider spread in results between strips from the exact same vial, so the fact that the old strips were so close to new ones was interesting to me. And four days after the strips expired, I checked my blood sugar (I was 263) and used a new strip to double check that (it read 262). A single point difference is pretty impressive.

So now I know that I’m safe if I use test strips a week after they’ve expired…which is great! But now I’m sort of curious to see just how far out from the expiration date I can use them. I might hang onto this vial of test strips for a few more weeks and continue to test them against newer test strips. I might not (because really, when it comes to diabetes, there are just more important things to be worried about…and I might not want to push my luck and end up wasting strips). We’ll see what I end up doing.

I think that the more compelling questions to stem from this experiment are 1) how many other diabetes supplies are safe (up to a certain limit) to use after expiring and 2) why are supplies labeled with expiration dates if, in the grand scheme of things, they seem to function just fine after expiring? Could it just be a nasty trick played on people with diabetes by prescription drug companies…?

Those are the kinds of questions that really make me wonder.