The standard is 30 days to expiration once an insulin vial has been started, whether a 10ml vial or a 3ml cartridge in a pen.
However, the shelf life unused while refrigerated is usually around 18 months (judging by the expiration date on my vials).
This got me thinking: What about a pen that is kept refrigerated, the end cleaned with alcohol before each use, and a new, sterile pen needle used every time... Shouldn't that pen be good for the full 18 months if kept refrigerated?
The 30-day timer is based on two main issues: Degradation of the insulin being stored at room temperature during active use of the pen, and introduction of contaminants when inserting the needle into the insulin in the cartridge.
Keeping it refrigerated takes care of the first, careful sterile procedure covers the second.
My reason for interest in this is I've been adopting intramuscular injections for doing corrections using disposable syringes. I'd much prefer to use a pen for this, however it's unlikely I'd use up a whole pen in 30 days since I pump for most of my insulin needs. What I'd like to do is just leave a pen in the fridge at home and at work, which would cover the vast majority of locales where I do corrections. If not at either place, no big deal -- just correct subQ with the pump.
Lantus is a pretty hard and fast 28 days, after opening. Its the most delicate of all the insulins that I have used. What are you injecting, specifically? I don't think your gonna, under any circumstances, get 18 mo. out of an opened pen or vial. It is strange, though, isn't it?
A few things make me optimistic this would work: The main issue is being allowed to warm to room temp, and then stored that way during use. This degrades insulin after about 30 days...
...but wait! Not so fast there! Many people have reported here on TuD about insulin vials lasting 60-90 days at standard room temp (72F/20C). This makes sense, as whatever limit the manufacturer specifies has got to have enough "margin" that, within variability batch to batch, it will still be fully potent at that limit.
So it's not too surprising that as a matter of course it typically lasts longer.
What if it was kept refrigerated, never allowed to warm up?
Second issue -- contamination -- can be addressed too.
So, under those conditions, only some volume is being removed -- the remaining insulin doesn't "know" any difference compared to if it stayed in the fringe virgin and unused.
What i do: after about 30 days, instead of usual vials, i use the insulin in the pen cartridges to fill my pump reservoir. that way i never waste any insulin. i also have a pen for emergencies/ IM injections.
I'll talk to my endo about getting 2/3 in vials and 1/3 as pens, and see if that will fly. Simply brilliant ideas, swiss! That way, I use it all up anyway each month without having to deal with expiration issues.
I can't speak to pens since I don't use them, but insulin is insulin so my experience may be relevant.
I keep all my insulin refrigerated, all the time. And while I do reuse syringes, I clean the needle thoroughly after each use. And I do not inject air into the vial from a syringe after it's been used once.
Result: I use each vial of insulin until it's all used up. Depending on a great many variables, that can be anywhere from 30 to 90 days. Knock wood, BUT -- I have yet to have a single vial go bad. Not one. Not ever. So far, anyway.
This is what I do, too. I keep a pen in my bag (so that it's with me everywhere) and every week or two will use it to fill my pump and replace it with one from the fridge.
Since I just use the pen cartridges to fill my pump (that can come out of the reusable pen - like little 3 mL vials) I use only pen cartridges and don't need regular 10 mL vials at all.
