Freezing insulin

[Tim]

I have a question – we all know that if you freeze insulin you’ll destroy it. So as you cool down insulin from room temperature there will come a point where it’s no longer any use. Is this a gradual thing – i.e. insulin becomes less effective the more “damaged” it becomes; or is it a binary thing – i.e. it’s fine until suddenly its ineffective?

Given insulin is a protein (I think!) I guess it would be more a binary thing – like frying an egg, it’s either runny or cooked.

[Tim]

In case anyone’s interested, I was wondering about this after leaving my spare insulin in the mini-bar of the hotel room I was staying in Oxford last week. It was a much colder mini-bar than I thought it would be.

[Peter Childs]

I’ve always been told it Binary if its Liquid and always has been its fine, If its solid its not.

However Insulin loses its effectiveness gradually if its kept warm for long periods.

[Annette A]

Insulin is indeed a protein, suspended in an aqueous solution. Once it freezes, it is rendered ineffective – because once it thaws, the insulin molecules clump in a different way, and dont work properly. But it does actually have to freeze and thaw before that happens. (And I believe the freezing point to be just below that of water.)

[Anonymous]

@tim when I was on pen cartridges & renting a place with an really, really over enthusiastic fridge I quite often froze novorapid to the back of the fridge through the cardboard & plastic packaging.

Only the end vial closest to the element would freeze & even then not fully because of the mass of insulin & the heat transfer propertys. That cartridge would seem less effective & I’d need a few extra units, played havoc with the lantus though.

Kept our insulin in many a minibar over the years w/o any problems & if you think about it miniatures aren’t that different in volume to insulin… The bigger problem is getting back to find your insulins been replaced by a bottle of bells ‘scotch’

[Author]

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