Insulin lifespan

I have a couple of questions regarding insulin lifespan. My doctor told me that once opened, insulin lasts the same amount of time at room temp as it does in the fridge. She also said that the max amount of time insulin lasts is 40 days, so I should throw out any insulin that old and start a new bottle.

  1. Is it really true that, once opened, insulin degrades at the same rate at room temp vs. the fridge? This seems to violate laws of chemistry, but maybe someone can answer this question who has better knowledge than my non-expert surmising? And if the degredations rates are the same, why is that?

  2. What are others’ experiences with how long insulin lasts? I’ve marked when I start a new bottle (I use Lantus and Humalog), and they never seem to lose potency for as long as it takes me to finish a whole vial, about 2.5 months. To see if this is merely me not noticing a gradual decrease in potency, I’ve paid attention to when I open a new vial to see how potent it seems in comparison, and no, there doesn’t seem to be any difference (i.e. no sudden increase in potency relative to my “old” vials). I hate to waste money as well as stuff that seems perfectly fine. Others’ thoughts/experiences?..

1 Like

Depending on my insurance I’ve been able to order between 1 and 3 bottles at a time for my pump - bottle now lasts me about 3 weeks. Out of habit (I was diagnosed in 1963) I’ve stored opened and unopened insulin in the fridge until I’m ready to use it, and change my cartridge every 3 days (maybe 4). I may or may not draw up a cartridge and take it out a few short hours before I’m ready to load my pump - I typically load at home but if I anticipate I’ll be away when I need to change sets I’ll take one with me. I’m typically in a vehicle or space with AC but may be outdoors for a while - I live in DC where it gets hazy got and humid.
Given that I use a pump my cartridge I may experience some less than ideal temps, but I attribute any high readings to miscalculation of carbs, even using CIQ. A lot of things can cause less then desirable numbers (however you define those) but personally I personally don’t believe “aged insulin” is one of them given my usage as described. Right now I use Humalog but previously used Novalog in my pump (not to mention good old NPH and Regular back in the day).

OK, Let’s start out with a fact. I’m an old school weirdo. That being said I have followed the same routine for storage of insuin for my 58 years and will continue to do so until the day I leave this earth. I use 10 mL vials and syringes for injections, you know dinosaur type stuff. The vials I currently have say they are viable until 6/2023. I store all of my insulin in the refrigerator even after being open because it states on the box that it has to be stored at temps below 77 degrees and if opened 42 days is the life expectency. The reason I always store unopened and opened vials in the refigerator is because if the power goes out and temps inside the house climb it could cause insulin to degrade and nobody wants that. If kept in the dark and careful temp control I believe that insulin will stay potent, but it’s my OPINION that cold dark storage is better than room temperature even for opened insulin. I see it as common sense because I look at insulin as a piece of raw meat. It’s sooo expensive, you want to cook it as soon as possible if laying on your counter and to protect it from pets, and if it continues to sit there for a week or so and the neighborhood raccoons and ravens haven’t eaten it, would you take a chance and then eat it? Nope, not me. I’m sure others will have different ideas and opinions so the end decision will ultimately be yours. I hope this gives you some ideas, sincerely yours, Mr. Dinosaur
P.S. treat your insulin like a cut of fine prime rib. mic drop

Thanks for the info. I’m a recent T1D-er but a dino as well - tried Dex., learned good stuff, now back to injections, liking that much better. Anyway yeah, cold storage makes sense for longer viability - not sure why my doc said otherwise… I use my vials for more than 42 days and haven’t seemed to have a problem…

1 Like

Excellent. If you keep it cold it’s like food, it will last longer than it’s recommended expectency because there is always a tolerance that has to be allowed for by the manufacturer so the longer you care properly for it the better, and you know that everyone prefers nice cold beer over warm stale beer. As you have personally found out 42 days can be stretched if you treat it right.

@BKN480 Only to add a few comments.

Insulin is a relatively tough molecule in the world of biotech. In a sterile, “un-pierced “ vial the only action degrading it is time and temperature (provided no exposure to sunlight). The packaging and formulation are tested to maintain original label strength through to expiry. After expiry, the molecule can break or cross link, making it less “insulin like” (loss of potency).

Once you suck in air from your non-sterile surroundings, as often done by piercing the stopper and (and you have to do this) blow in 5 units of air to suck out 5 units of insulin. you challenge the sterility of the vial and (verified by testing) after 40 days you should toss the vial. This doesn’t mean the insulin breaks down, it means the sterility breaks down. So that’s why the printed documents say what they say.

Now nothing magical happens the day after expiry or on the 41st day of use. It’s just not tested and you are playing a statistical risk game where the odds double every so often.

Hope this helps.


Here’s one more opinion - I started taking insulin in 1956 and never have I (nor my parents when I was younger) thrown away a vial of unopened or opened insulin. I do, however, keep all vials in the refrigerator.

What comes to mind about this is that ALL insulin for a lot longer than the 65 years I have been taking it has had a Cresol compound added to it to kill any invasive mcrobes. You can smell it if any insulin is exposed to the air: it smells like older telephone poles, which are coated with creosote, a related chemical. When have you heard of a telephone pole being rotted through by invasive agents?

@tedquick yes. however, telephone poles rot anyway, but the creosote prevents it from happening right away. Just like insulin will eventually be overcome if it is exposed long enough. Anyone who ever had a septic tank knows why. cheers!