Don't waste insulin with a new infusion site (Tandem X2)

I’m a 40 year Type 1 and very recently switched from my Medtronic pump to a Tandem X2 (very slick user interface!!). I was setup to use Control IQ which, for me, is a work in progress as I try and figure out basal rates compared to what I had with my Medtronic (I’ve seen many posts about basal differences between pump manufacturers). I have always had, what I’ll call, an insulin effectiveness delay when using a new infusion site and normally do some shot supplementation for the first few hours post-insertion. What I found is that if I have Control IQ enabled the pump’s algorithms will continue to increase basal rates and give micro-boluses as my CGM readings rise due to the lack of insulin effectiveness…this I view as a waste of insulin. What I just determined is that I can save insulin by disabling Control IQ upon insertion of new infusion set, supplement with shots (if needed) and then enable Control IQ after a few hours.

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Curious. Have you actually crunched the numbers and determined how much more insulin Control-IQ is giving you than you are injecting? I’m wondering what the difference is.

It’s actually really normal to require more insulin after a new insertion. It’s the one and only thing I learned from my pump trainer. She told me to use the largest cannula fill volume option (0.7u), even though my set only requires 0.3u. She said that fresh sites don’t absorb insulin well until they’re flooded with insulin. I’m not very sensitive to insulin, so I’ve since switched to a full unit cannula fill (the largest manually entered amount you can use), which seems to avoid the new set spike quite well for me. I don’t want to bolus that volume because it’s practically inert and not affecting BG. The fun cannula option is the only way deliver invisible insulin.

Also wondering if you’re running in default mode or full-time sleep mode, as the default mode doesn’t actually increase basal until you’re already over 160, at which point you might already be becoming more insulin resistant, requiring even more insulin for corrections. Whereas sleep mode starts giving extra basal at 120, where your insulin is more effective.

If you know you’re going to need the extra insulin, always better to give it sooner than later!


Hey Robyn…good call out on the modes…just made the switch to sleep mode to see what happens. Grats!!

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I do the same, but do .6 fill twice (on Tandem) to get 1.2. With medtronic, did similar “overfill” cannula because that’s what worked.

I not only run sleep mode but I also decreased my insulin sensitivity to get better control.

I don’t understand how you come by wasting insulin though.
If insulin is being pumped into u they you have it in you
I don’t see how it is wasted.
If it’s not absorbing then you need more. I don’t see how it will be any different than injecting a new spot with a needle.
I inject 2 units when I change to a new set just to fill up the new void.
And also how much insulin are we talking about for you?
I mean just using a pump wastes at ton of insulin in the tubing and reservoir.
Your first few hours on a site can’t really account for much or can it?
I use humalog which should be thrown away 2 weeks after you open the vial. I don’t use it so fast and it’s fine to use for 3 weeks but I feel like I’m getting all that third week insulin free, so I don’t mind if it gets a little wasted in a pump priming and all that.

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I’m curious and plan to monitor my post set change numbers. I’ve never paid enough attention to post set change numbers (probably because I change before bed even though I know you’re not supposed to).

The major curiosity, though, is do you make sure and leave your previous set inserted for at least 3 hours after you stop using it? I was taught that you can’t immediately remove the old set because removal could allow infused insulin to leak out of a “tunneled” site.

Me too!

I have had a similar problem. Not for every infusion set change, maybe 40% of them. Typically I would have high BGs for 8-12 hours.
I guessed the new infusion set needed time to get “wet” to work properly.
I have found something which has pretty much solved the problem for me. When I insert a new infusion set in the morning, I leave the old infusion patch in and attach the pump to it. I set an alarm on my watch for after dinner. When the alarm goes off, I transfer the pump to the new infusion patch and remove the old infusion patch.