Tandem decision

The most informative review of Control IQ I´ve read so far is from Alicia Downs at Integrated Diabetes. She uses sleep mode only at night and still found it to get her tight control and an A1C of a 6. But she had to understand sleep mode to get there.

Her full review here.

I´m using a Tandem loaner pump with only Basal IQ at the moment, and find the change of infusion sets the same as when I used Metronic pumps or I had an Animas pump. Not much different. Just make sure you have enough insulin to fill the tubing again if you need to change inset.

Personally I´ve never yanked out an inset so I guess I´m lucky. Pluss I always secure the tubing like this:

I find the filling of a new reservoir quite simple too. No problem so far.

And I like the way Tandem thinks. They are the first company to be approved as an ACE-pump (alternate controller enabled) which means you can use the pump with different components. Connection to Libre is coming so you get to choose CGM-system. That comes in handy if you for some reason have to change your CGM-system.

And you get to upgrade your pump so It doesn´t get old that fast. As I understand it Tandem listens to their users and integrate new features based on that.

I find many things to like about Tandem so far.

Best of luck with your decision, @DrBB.

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Hey, that’s a clever hack—all this time and I’m still learning stuff around here!

And thanks for the link, I’ll check it out.

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Having read the Alicia Downs article: a very helpful, detailed account that answers a lot of questions, including some I didn’t know I had. Lots to ponder.

Main takeaway is that, yeah, like the MMT systems, there’s going to be a lot of tweakage involved. Same lesson I learned there, which is that the values you enter for things like sensitivity, correction ratios etc, are going to be based on what it takes to force the thing to do what you want it to do, not on what those values objectively measure out as. It does look like you can actually tweak them, though, so that’s something. What’s totally different is that in the 670 a lot of the things you could tweak for manual mode had absolutely NO impact on Auto. The only one that really mattered was DIA. And even at that, you couldn’t take it below 2 hrs, if memory serves. But with Tandem you CAN’T adjust DIA: it’s hardwired at 5hrs, which is a LOT longer than I even use for my manual pump. So right off the bat I’m going to have to be faking up values for the other parameters for C-IQ to have any chance of working for me at all.

In other words, yeah, back to that whole mess again—the whole reason I’ve been procrastinating this decision and sticking with the pump I have. It’s dumb but reliable. Only now “reliable” is dropping out of the equation.

All along that’s been one of the strongest things in Tandem’s favor, for me as a tech guy. Always amazed me how far behind the times these devices are in that respect.

It’s because of the bluetooth connection. You can definitely just stick it in your pocket without a clip/case and I’ve done that a few times.

Tandem is far more customizable. The only thing you can’t change in CIQ is the insulin duration time which is set at 5 hours. I thought that would be a problem but it isn’t, especially with the way the pump calculated IOB. It uses both basal and bolus but it will also subtract IOB when it decreases or stops your basal.

Last night was my second night with my new basal profile and I am really happy with the results. Basically I just created a profile with a flat 1 u/h rate, keeping my I:C ratios and correction the same as before. My 24 hour basal on Medtronic was 12.2 units so creating a profile that was double that amount had me a little worried, but the pump seems to be taking care of it with the CIQ adjustments. By having the higher rate, when CIQ decreases my basal it doesn’t do it as aggressively as when my rate for that period was maybe .45 u/h. When it’s suspending insulin it’s doing it for shorter periods so I’m not seeing a rebound high. My total basal for yesterday, my first full day with the new profile, was 16.64 units so definitely higher than Medtronic but I wasn’t dropping low from it.

It is easy to override the bolus suggestions made by the pump if you feel/know that what it says you need is wrong. I love that you can do a dual/extended bolus (only for a maximum of 2 hours). There’s no worry about confusing the algorithm if you do a manual correction after waking up to take care of a “feet on the floor” rise. I’m currently trying to see if CIQ can handle it without me correcting. I tend to forget that it has been increasing my basal so I don’t have to be aggressive with a correction.

My TIR has been amazing with this pump and I have far fewer lows, which is what I want. I am 100% glad I made the switch. My biggest complaint is the lack of choice in infusion sets. I’ve already had a few mishaps with the Autosoft 90 getting pulled off when I lift the inserter off, even though I try to hold it there for a bit after insertion. I’m just going to have to keep using SkinTac I guess.

From my possibly flawed understanding, this is not completely correct. Although insulin on board is measured over that period of time it diminishes by successive half-lives, meaning if you give five unit of units of insulin right now, in an hour it will be 2.5 IOB (insulin on board), in two hours 1.25 IOB, in three hours .62 and four hours .3, and basically 0, 5 hours out.

Although those numbers in may not be exact, they reflect my understanding of how the duration of insulin action calculation works with Tandem. And it makes sense to me.

If somebody has a different understanding, I’d be interested.

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To clarify a bit, they do use a fixed 5-hr value for DIA in CIQ mode because the algorithm needs to be a lot more accurate to how insulin duration actually works, and the profile reflects some fairly extensive research on that. As you point out, it’s not linear but I’m not sure exactly how it’s defined. Pretty good discussion here, though it’s a couple years old now:

In manual mode DIA is still user-adjustable.


@PYBM I absolutely LOVE my Tandem (would not switch) & also came from Animas when they went out of business, but I agree 100% re: Tandem cases; they are horrible! I have moved to wearing clothes with a pocket that stores the pump or wear it in my pants pocket. BTW if you liked the Animas pump case that had the locking, spin clip, you can buy that here: Generturbo Insulin Pump Case for TSlim https://www.amazon.com/Generturbo-Insulin-Pump-Case-Accessories/dp/B0BJ6LT1XQ

Sure is a lot of misinformation here about the Tandem pump and how CIQ functions. There are no issues with a cartridge bag over a syringe, 30 yrs pumping, it’s a loud online myth perpetuated by user who won’t learn how to do it and a medical profession who won’t teach how. The key to success with CIQ is dependent on getting basal rates setup correctly to match your T1D physiology, not the algorithm. The myth about the degradation of insulin in the plastic has no clinical basis with current pump approved insulins. Running the T:Slim in sleep mode is similar to Basal IQ with the added function of increasing basal rates to counter a rise in BG. However, this does mean that you have to understand insulin action and initiate correction bolusing when necessary. The confusion about DIA is based on the misunderstanding of the setting. The Tandem CIQ algorithm uses the actual DIA and that averages 5 hours with the pump approved insulins. Other algorithms provide an option to customize what they call duration. However, the time you are able to modify is actually IAT, the time the insulin will act to lower BG, and can vary individually. DIA refers to the amount of time it take for the insulin impacts BG to keep it from rising.

@DrBB I have the same 522 pump, and I’m wondering what reliability issue(s) you’re experiencing?

Like you, for several years I’ve wanted a Tandem tslim, however they weren’t available until a couple of months ago. Now that they are I’m hesitant to change as I’m comfortable with the performance on the 522 (and I like the smaller form factor) :thinking:.

My control and TIR is excellent, something I’m pretty sure I couldn’t duplicate with the X2.

Thanks for the suggestion. I never used that clip with the Animas pump. I just used the clip that came with it. It worked perfectly for me. I like to wear my pump clipped to the middle of my bra. That worked really well for the Animas and Medtronic pumps, but not Tandem. In order for the pump not to show up as a large rectangle under my shirts, I need a clip and case that don’t protrude too much. The silicone case and phone clip are the best I can find, but the pump still shows under my clothing. I have to tuck it under my bra now, in the middle and it bugs my skin.

I used 3 different MiniMed/Medtronic pumps for about 20+ years. I made the change because at the time Medtronic wasn’t making any big changes. So I made the switch and haven’t looked back.
The cartridge change takes a little longer. It takes about 6 minutes. Yes, longer than Medtronic but it’s 6 minutes. I sleep through the night without alarms!!! That was a huge selling point for me!
I do not use sleep mode all day and the reason is, I don’t want to work at this darn diabetes stuff. I like that my pump now does it. I don’t have any DP but I do have FOTF problems on and off. And my doctor smartly suggested leaving my sleep mode on for a few more hours each morning, which has helped greatly with those mornings when it happens and when it doesn’t, no problems.
I’m guessing you have played with one so you know about button pushing (some things take a lot of button pushing), sunlight issues ( I just move my body to block the sun), cartridge changes are no longer an issue as I have been using the pump long enough it is my new normal, I use the same kind of infusion sets (TruSteel) but some have to use different infusion sets.
I have also had no problems with service calls, but I really have not had any problems. My biggest issue is I have to use a supply company. Sometimes it can be a pain, when your insurance company changes which company you can use. Back in the day, I ordered directly from Medtronic. Oh the joys of insurance companies!
Good luck with your choice. I will say, the switchover was pretty seamless, even after all those years using MiniMed/Medtronic pumps?

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Mine’s a 522/723, but close enough. Last two battery changes it has come up displaying a numerical E code that translates as “Batt Out Limit Alarm,” meaning the battery was out too long, defined as five minutes. But that was erroneous. Both times I had done the swap in under a minute, as I routinely don’t take the old one out without having the new one right there ready to go. Both times I had to reset the YDT, which had gone to default values, Stuff I’ve never seen before in the 10-odd years I’ve been using it. I called MT tech support the first time it happened and they said if it kept doing this it was probably going to crap out on me at some point. I was hoping it would cure itself, but the next battery swap also ended in the same error. The second time it ran a countdown on the screen before I could do anything, probably indicating some kind of self-check was going on. I was afraid it was going to hit zero and say Fatal Error and I’d be SOL, so I’m kinda dreading the next one. Figured I’d better at least have started the process of getting a replacement before that happens.


You need Nite Ize Hip Clip:

(Sorry to hijack your post, @DrBB).


No problem—it’s all useful information relative to my decision.

Not sure it will make you feel any better, but my pump used to do this on a fairly regular basis, but it hasn’t been a problem for 12-18 months now. Hopefully it has another couple of years left in it :crossed_fingers:t2::crossed_fingers:t2:

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@Laddie suggested that I get one of these clip holders and I love it.


That’s the one I have. The sharp edges of the metal bother my skin and now, after having it for a year, it doesn’t grip very well, because without a spring at the top, the metal eventually bends out and it’s slippery because it’s just metal with no rubber or plastic grips. I mean, it’s better than the other ones for the Tandem, but still doesn’t fit my needs. My daughter is doing her degree in Interaction Design. For her thesis, she’s suggesting alternative designs for a clip that would work better. I think I’m just exceptionally fussy. LOL.

I’m not a pump user but I have designed and built some electronics projects and that sounds like whatever Medtronic used to power the CPU and Real Time Clock while the battery is out is failing. You said the pump is 10-ish years old and that is about how long some of those “supercapacitor” or similar devices last.

Bad news is the problem can’t be fixed. Good news is, if I am correct, you can keep using your pump till something more serious goes wrong if you are willing to reset the clock during battery replacements. I looked up the manual, you also need to check that the pump hasn’t reset to defaults and if it has do a settings restore.


Technical details—me likey! That does sound like a very plausible/likely explanation. Always kinda wondered what these (and other) devices use to stay “alive” during battery changes. Dunno if it’s related, but the interval between battery swaps is definitely shorter than previously. One of the things I like about the old Paradigm is how long the battery lasts, but that’s definitely on the wane now too. Used to be a solid three weeks or so, but now more like 10-14 days. That seems to have developed fairly recently, like the last couple of months.

On a side note, I was surprised to find that the age of your pump is apparently not per se an automatic justification for replacement under Medicare. The 670G, even though I don’t use it, is on my record as my most recently purchased pump, and it’s about 6 years old, so well past the 4-year warranty as well as the 5-year interval specified by Medicare. At first the Tandem rep said, “Fine, no problem,” but then came back and said that, being it’s Medicare, it would be, um… easier… if I could attest to any item on a list of condition issues to help qualify for replacement. Cracks in the case, problems with the battery cap, sticky buttons, etc. Decreased battery life was one of them. I’d certainly have no problem attesting to that on my Paradigm, but that’s not the pump they care about. I did get the 670 out of the box and give it a long, hard perusal…


When I was an avionics technician in the USAF we were expected to fix every problem in every set. If it was beyond our abilities the set could be sent to depot for repair, but this was frowned on by the PTB (overlords). The joke when facing a difficult problems was, “Opps! It feel off the work bench.”

Never saw that happen but it could happen to the 670G. I won’t tell. :smirk:

I do remember one set that was sent to depot for advanced repair. It was a frequency tracker for a Doppler navigation set. These things were about 3 feet long and say 9” x 9” cross section. In the plane they were housed in a metal box.

When we got it out of the shipping crate, surprise, surprise, surprise - it was twisted along its length about 45°. Curious we hooked it up to our test set up, and it worked perfectly. No way it could be installed in the plane, so back to depot. We never found out what happened to that thing. We think the depot yahoos would send it out to various units as a joke - your tax dollars at work.

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