Insulin below freezing -- should we risk it?

WE just came back from two weeks of vacation and the MedAngel thingie I set up in my son’s insulin read 30.8 degrees Fahrenheit. So below freezing – yikes! I noticed part of my beverages in the fridge had some ice in them, but I can’t see any visible ice in the insulin penfills we have.
Does anyone know if insulin has the same freezing point as water, and if so, what happens if it’s briefly below freezing? I have no idea how long it was below freezing, unfortunately. We have tons of spare insulin in the fridge – probably months worth – so it would be a shame to discard.

Chris had his frozen insulin experiments where it still worked but had a longer activation profile. I think the freezing point is pretty close to water. I’d probably give it a try with a lot of testing on the suspicious vial to see if it’s working like usual…

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I’ve had hotel fridges go down into the mid 20s a number of times on me and my insulin had never actually frozen. I don’t know what the true freezing temperature of insulin is, but it’s definitely well below waters freezing temp.

I think your insulin should be fine…

If there is little to no cost pressure involved, I would not use it.

There are so many questions about why this and why that. For me it would not be worth introducing yet another uncertainty.


Where in the fridge was it, and how was it packaged? If it’s on the door or in the butter thingy, those places are usually warmer. If it’s in its box, it’s further protected by that and the foil cartridge surround (minimally, but maybe enough). We keep a big water jug on the top shelf and it sometimes freezes over, but the insulin (at the handle end of the door) has never been affected. Maybe try one refill with that insulin and see how it goes before you throw everything out.

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I will tell you that the freezing point is well below water. We kept small residual amounts in a vial in the freezer for a week, before we turned our freezer down, and eventually went to the deep freeze in order to ensure the insulin was visibly frozen.

I personally woulnd’t worry too much, but if you are worried, I would follow Thomas’ advice.


Interestingly I haven’t been able to find a proper description of the actual freezing temperature… should be a fairly simple question to find the answer to, but seemingly it’s not.

I am 100% certain it’s appreciably below waters freezing temp…

I spent 30 minutes doing that at 4:00am when I read your query :slight_smile: But I did not find the answer either.

This is @Chris’s insulin freezing experiment: Does Freezing Humalog Destroy It?

This is @Eric’s unrefrigerated insulin experiment: My insulin experiment for Michel...Relax everyone!

Both were enlightening to me. @Chris’s answer on this thread was extremely valuable to me in gauging this:

as was @Sam’s:

This indicates to me that the freezing point for their insulin must have been quite low. @Chris, was that the Humalog of your experiment?

While I tend to believe the insulin is likely OK, I also feel like @Thomas:

What about doing a timed experiment to see how well it activates? If the activation curve is normal, I would feel comfortable that it survives unscathed.

My conclusion from this thread, though, is that it is likely, from a preponderance of evidence, but not beyond a reasonable doubt, that the freezing piont of most insulins is somewhat lower than that of water.

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Mine was unrefrigerated and expired, I have some frozen stuff but I haven’t injected it yet. I only have the unrefrigerated and expired, and the hot car test.

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2 posts were merged into an existing topic: An experiment to measure freezing temperature of insulins?

I have had insulin semi-freeze into a sludge state in a small “college style” fridge. We did not use it.

(It was not our fridge. Pharmacy related. Not only am I more careful now but SURPRISE they know me by name. ha ha ha)

First point as mentioned, we already deal with too many variables.
Second point, it would not be used on me personally.

So sorry, typo, I relabeled it :slight_smile:

Yeah those inexpensive dorm room/ hotel style fridges use really low quality thermostats and are notorious for poor temperature control. I wouldn’t use it either of it was visibly frozen, but I’ve seeen them get very cold, without freezing my insulin

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5 posts were merged into an existing topic: An experiment to measure freezing temperature of insulins?

Yes, my experiment was Humalog

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A post was merged into an existing topic: An experiment to measure freezing temperature of insulins?

The vial of insulin does not all freeze a the same temp. The freezing point is below 32. The water suspension will freeze first, followed by all the solutes - for Humalog it’s insulin lispro, glycerin, dibasic sodium phosphate, Metacresol, zinc oxide, phenol.

You can tell if Insulin is frozen by looking at it. If you don’t see ice crystals, it’s fine. But if you see the crystals formed, be safe and get a new vial.

You might be able to get some use out of it - I wouldn’t throw it out if it was all I had - but once’s it’s been frozen the strength and efficacy can be affected. If you have more insulin, ditch any vial that had crystals formed in it from freezing.

@Erioc, I split your post between both freezing threads, hope it;s OK!