Pre-fill Tandem cartridge for a trip?

I’m heading away from home for 3 days and unfortunately my reservoir-insite swap is going to land in the middle of it. It’s never convenient to do those swaps while traveling, staying at someone else’s place, lots of stuff going on. I was thinking about filling a cartridge before leaving and bringing that along, since that’s the messiest/finickiest part of the procedure. Anyone done this before or have a good reason why it’s a bad idea?

I will be doing this on my upcoming trip. But in addition pack additional cartridge, insulin, sensors, etc just in case. I always plan for possibility of being away longer than I think due to weather or other circumstances.

And always include syringes or pens as backup.

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Well the thing they tell us is thst plastic will cause insulin to lose its effectiveness. Thats why it’s still sold in glass vials.
So everyone suggests not pre filling them.
My guess thst it would be fine for several days, but I’ve never attempted it. Filling the cartridge with insulin isn’t very difficult.


The reason for not using a T:Slim cartridge and tubing more than 3 days is reactions between the preservatives in the insulin and the plastics. Some people may do well extending the life of the cartridge beyond 3 days. I notice a reduction in insulin effectiveness sometimes as early at 2 1/2 days.

Those who are more insulin sensitive and have lower basal/bolus amounts might be able to extend cartridge life.

This link is to a 2020 article on the development of a new insulin type designed to reduce the problem.


My concern would be the lack of sterility of the open end of the cartridge pigtail. It would be great if Tandem could provide sterile caps for the cartridge. Back in what I consider the good old days when the the cartridges had Luer-lock ends, I could get caps gratis from the cancer center. That allowed me to pre-fill cartridges for trips up to a week. But alas, Tandem wanted to follow the Medtronic path of have everything being proproetary.

You could take tubing from another infusion set and cut a short tail to cartridge pigtail.

Or store the cartridge in baggie.

The problem with insulin and plastic is that the preservatives in the insulin are really volatile and can escape through the plastic. The insulin doesn’t break down or anything, but the molecules can clump together, leaving you more prone to occlusions.

In my experience, though, I’ve found that the insulin can still withstand quite a long exposure to it, much longer than the “rules” suggest. I think I would be fine with a pre-filled cartridge for that number of days, but I can’t really comment on you. I think you should test how well you tolerate a pre-filled cartridge in the comfort of your own home rather than on the road, and just make the time for the tiny inconvenience of filling the vial this particular time.


Unfortunately, neither of those are a sterile procedure and could make you at risk for a systemic infection.


So, it went fine. I brought extras of everything just in case but didn’t have to use them.

Cartridge seemed to last fine for the whole 3-day period (I just swapped it out yesterday).

I put it back in the original packet after filling and taped it shut. Maybe it’s just luck but I’ve gone for more than a decade never using those little cap thingies they send with the box of insets when I shower or whatever. I just never remember 'em. So I’m maybe less paranoid about infection that way than I should be.

Anyway, thanks for all the feedback. Not sure I’d recommend this as a general practice, but I always find it awkward dealing with this stuff when I’m away, and knowing my reservoir was going to run out in the middle of such a short trip pushed me to try it. Alternative would have been to go ahead and swap it out the day before leaving, but when you have a good insertion site going and a day-plus of insulin left in the thing it seems like a waste to do that.

Also my Dexcom session was scheduled to end on the same day! That was easier to deal with of course. I always try to pre-soak for 24 hours, so swapping sensors is just a simple matter of popping the transmitter out of one and into the other. I had a musical performance to do, lots of set-up, sound-checking and rehearsal, uncertain about accommodation for doing all this stuff or when I’d be free to skip out and deal with it while that was going on, so just trying to simplify things as much as possible. I wouldn’t have tried it if I was going to be away for a week or more.