Insulin supply management?

I’m wondering if something I’ve been doing recently to extend my usable supply of insulin is a bad idea.

I’m on a pump (Minimed 530G) and using Humalog in it.
As anyone who’s used one of these pumps knows you’re supposed to change the infusion set and reservoir every 3 days and I’m pretty good about this.
So, now the question.
There have been several times recently where due to impending activities (a flight to Alaska, moving to a new residence) it was much more convenient for me to change out the infusion set early.
This means I’d be throwing away a significant supply of insulin.
Rather than do that I connected the reservoir that I’d just removed from the pump to the new reservoir’s needle adapter (not sure what to call it) and squirted the insulin remaining in it back into the vial of fresh insulin.
Is this a bad idea?
I noticed no change in the effectiveness of the insulin as I used the remainder of the vial.
I always keep the vials refrigerated, otherwise they’d expire before I used the whole thing.

Wheelman

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yes that is a bad ideal. Insulin in the reservoir starts to degrade and placing it back into a vial of fresh insulin can cause problems since your mixing degrading insulin in with fresh insulin. If you know your going to change for set and reservior early why don’t you look at your daily totals on your pump and calcualate what you need plus a little more so when you change early you don’t waste a lot of extra insulin.

Do you use up an entire reservoir in 3 days? I fill mine with 300 units and it lasts me about a week. I don’t change it until it’s at or near empty. I don’t have any problems doing this and doing this doesn’t compromise the insulin that is left in the vial.

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I now do the same practice as @Scott_Eric. I fill my reservoir up to its 300-unit capacity. Since I only use about 30 units per day, that reservoir lasts about 10 days. I have not personally experienced any questionable blood glucose levels due to insulin degradation in the resrvoir.

I used to change my site and reservoir at the same time and that meant I estimated the insulin needed for three days. I still change out my infusion sites every 72 hours. Site changes are simpler now as I just need to insert the new cannula and then move the supply connection from the old site to the new one.

I agree that mixing old insulin with fresh insulin is likely a bad idea and easily avoided using a routine like I use.

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I frequently cannot even make it to 3 days before needing to change infusion sites – and like @Scott_Eric and @Terry4 I frequently continue to use the same cartridge and insulin with a new infusion set. I have experienced no degradation of the insulin in the cartridge.

Unlike the others, I have been known to (frequently :slight_smile:) add insulin to an ‘old’ cartridge when changing out only the infusion site. Again, I have not noticed any degradation of the insulin action as a result of this.

The only degradation that I’ve seen is when I leave a site in too long – and, for me, that can vary greatly from as little as a day to three days, depending on how much insulin I needed/pumped during that period. I go through a great deal more infusion sets than cartridges or even tubing.

Humalog can remain in a cartridge for no more that 7 days per its FDA approval data sheet. There is also a concern that after 3-4 days the cartridge itself with insulin present can start to degradate leaching chemicals into the insulin.

My process is similar to Terry’s. But I have 1.8 reservoir which lasts me about 1 week. So I do insulin about once a week and new infusion set about 2 times a week.

I never put insulin back into bottle from a used reservoir or add insulin to reuse a reservoir

However, when time to fill a new reservoir but not enough insulin in the current bottle. I will do the following.
Estimate how much more I need in old bottle. For me, with bottle inverted, it means up to where the label is.
Then with new reservoir, take out some insulin from New bottle, and then add that to old bottle.
Then do complete fill from Old bottle, which should use all that is there.
This prevents any contamination of new insulin bottle, and minimal amount left in old bottle to throw out. And always starting with a full reservoir each time.

I should note, that I fill my reservoirs from pens – so there is no possibility that insulin from the reservoir will be pushed into the vial – I push the insulin out of the pens using the pen mechanism.

I started pumping before pens were available, so have NEVER even used a pen ! Prior to pump I was using NPH and R. Started on the pump with R. Humalog and Novolog were great improvements.

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I used to fill my 315 unit cartridge and run it to the end. I could go anywhere from 9-11 days. Now I try to estimate a weeks worth of insulin and change when it is almost empty. I never go more than three days on an infusion set. Lots of times I am lucky if I can get three days. I never put old insulin into a bottle of fresh insulin.

To answer the question of how long a reservoir lasts me.
My daily usage varies from ~25 to ~30 units and I fill the reservoir to 100 so it’ll definitely last me at least 3 days.
So, if I was to completely fill the reservoir (1.8 ml or 180 units) it would last me a little less than a week.
I’ve always replaced the reservoir when I change the infusion site with the exception of the infusion site being yanked out really early. Then I insert a new one and continue the reservoir as is.

I got my question answered though, and I thank you all for the information. I’ll stop putting “old” insulin back into the vial if I decide to change out the reservoir/infusion site early, I’ll just throw it away.

Personally I don’t think I could stand to leave an infusion site for more than 4 days, they start to itch by the 3rd day so I’m usually ready for a new one. This isn’t always the case, some sites are not sensitive but that’s the exception for me.

There is absolutely no reason that you have to change the reservoir at the same time that you change the infusion set. The only reason the pump companies say to do so, is that they haven’t actually done the fully controlled tests to check if the insulin is stable for more than three days. However, lots and lots of people use their reservoirs until they get really low and I have never heard of any reports of problems. I change my infusion set every two days and my cartridge when it gets below 10U. That takes typically about 4 days and I am aware of people going for up to 6 days.

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It also does depend on the pump. When we were on the Animas Ping and using the infusion sets (the ones that look like a yo-yo) it really was not practical to just do the one without the other. We could do it and did sometimes for an unusual situation but the way it all hooked together did not really make sense to us to separate the two actions as a normal practice.

Now on the Tandem, they really are two separate actions. The biggest reason we do it together is simply convenience and not having to remember a different schedule. Not a big deal but enough so we just do them together. Plus being used to changing the insulin and infusion set at the same time from the Ping probably makes us more comfortable with doing it similar with the Tandem.