Tandem pump users

Changed pump, had to start a new bottle of insulin mid change (other bottle ran out)…When I put half-filled syringe into new insulin bottle, some insulin from syringe sucked up into new bottle of insulin. Now there’s extra insulin in vial. Will this affect the concentration/dosage of the new insulin vial when I re-drew the rest of the insulin from new vial into syringe?

Technically, I believe it will. But I think it’s likely you’ll detect any difference, given that your old vial and new one still contain sufficient potency.

As insulin users, we have no method to easily test the potency of any insulin source. You’ll just need to keep a careful on on your blood glucose data when using this “mixed” insulin. I believe it’s highly unlikely you will detect degraded potency.

That’s a good question. We all need to watch our CGM and/or fingerstick meter to monitor questions like this.

Thank you for your reply. I mean if there is more/extra insulin in a brand new vial (from the old insulin pushed into it from syringe), would that make the concentration more than normal, so you’d need less insulin? Or would it be that since both insulin vials used were the same concentration, it wouldn’t make a difference if the brand new vial had over 1000 units in it and one unit is still ‘one unit’ drawn out in pump?

Though I didn’t think of it like that, that the old insulin pushed in could ‘degrade’ the newest insulin vial potency so good question? I’d think not since both vials I used are fairly new?

No. Insulin in your half-filled syringe is likely slightly less potent that the insulin in the fresh vial. So mixing a small volume of less potent insulin will have very little total effect when mixed with a relatively large volume of fresh insulin and would theoretically make the total mix less potent. But that effect is miniscule and I don’t you would ever notice it.

Insulin concentration is measured in insulin units per milliliter. A vial that’s overfilled does not, by that measure alone, become more potent. Am I understanding your question?

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Thank you for your replies, it is helpful. That’s what I thought, that it’s measured in units/ml so it wouldn’t change the concentration, but I just called the Lily company to make sure (I use Humalog). They said they didn’t ‘think’ the ‘concentration’/dosaging would change ( I guess they weren’t SURE?) but said the ‘potency’ could be affected since it’s mixed insulins now of different ‘in use’ times, so they said that could affect the ‘potency’ of the insulin, and suggested to not use this new vial and/or the cartridge of insulin I have now on the pump w/the mixed insulins, and change the current cartridge.

So I guess concentration is different than potency, but I thought as much, like you mentioned, that the concentration per unit wouldn’t change from the added volume of insulin to new vial.

Lily suggested if this happened again and I run out half way through a pump change, to use a separate syringe to draw from new vial the remaining insulin, (as to not mix them if the old insulin got sucked into new vial from syringe), and enter it into cartridge like that, but then I just thought, well that’s still mixed insulins in the cartridge then!?

But I’d think I shouldn’t need to go change the whole cartridge now if we’re sure the concentration is same and potency might be a little less. ! Hasn’t this happened to folks before?

Thank you for your time good sir! Sorry for the novel, have a good one!

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I think they’re just covering their asses. They want to make sure that they don’t make any statements that could later come back as a liability case for some reason or another.

I wouldn’t worry about it too much, but that’s just me.

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Concentration will not change.

Potency could have minor impact but hard to imagine enough to make any noticeable difference.

I would give it not a second thought.

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I believe these are two words describing the same thing, in this case insulin units/mL.

Lilly is always going to recommend the least risky path. That means discarding anything that you described as a “mixed” insulin and replacing with fresh. If I was faced with this situation and money needed to be a factor, I would keep the insulin in the pump and monitor appropriately. Do you use a CGM?

As I mentioned earlier, the impact of the “mixing” process you described is negligible. You would not be able to detect it.

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I can’t see any way this should matter. The concentration/potency of your insulin is the same the same, no matter what. The exception being that the older stuff will have degraded slightly, but a miniscule amount of older insulin mixed in with the new shouldn’t cause a noticeable effect. You’ve only changed the volume in the new vial, and not the effective concentration of the medicine within it

It’s sort of like when waitstaff top off a half-emptied glass of unsweetened iced tea. The glass is refilled, and the volume has increased, but it’s still the same tea you were drinking before they refilled it.

Like others, I believe you’ll be fine and not notice much difference for having mixed the vials. But, I’ll add this. Insulin degrades over time, with wide fluctuations in temperature and by bacterial contamination. Every time you introduce a needle into a vial you risk micro-contamination. There is no getting around this and best practice is all you can do. Part of my best practice, when needing to use up insulin in one vial before going to the next, is to draw the newest vial into the syringe first then empty the older vial by drawing it up last. The insulin will be mixed but you haven’t taken any potential contaminants from the old vial and introduced them to the new.

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I like that one !!!