Tandem decision

My old legacy, pager-style Paradigm is at last giving signs of impending software failure, so I’m facing the prospect of getting a new pump, which I’ve been putting off for years. Question is Tandem or Medt (I’ve looked at Omnipod, but it’s not for me). I’ve done enough research to know a bunch of the pluses and minuses. Would help to hear more about peoples’ experiences, especially any long-time Medtronic users who have made the leap to Tandem. For me it’s basically coming down to whether that finicky finagling bladder-and-syringe insulin handling component of Tandem is offset by their AID system, in whichever of the configurations (Control vs Basal IQ) I’d end up using.

  • Can anyone tell me more about running permanently in Sleep Mode for the more aggressive target? Says here the “setting does not allow any auto-correction boluses while it’s activated.” Not sure what they mean by “Auto-correction bolus.” Guessing that refers to the correction bolus Control IQ will give you in regular mode, but you can still give yourself one manually? Or you can’t bolus at all without switching sleep mode off?

  • Is that process of changing infusion sets really as much of a PITA as it looks? Like at 3am with a sleep-fogged brain because you rolled over and yanked your inset out and all you want to do is get a new one in and back to sleep before the sun comes up? What about that old-school THWACK OUCH! inserter, same as the old Mios before introducing the Advance, which was a godsend? Really don’t want to go back to that, but if other things seem worth it…

I know every system has things that will drive you nuts after a while, just a matter of choosing which ones you can tolerate best. If only you could combine the best of both systems and leave the sucky bits, we’d really have something. But that’s just not how it works alas.


I switched to Tandem X2 from Medtronic 523 about 3 years ago. Started with MedT in late 80s, I think Model 506?

The transition was pretty smooth, and got used to the funky cartridge. Miss the Quick Sets (easier, less waste infusion sets). But ok now with the Tandem XCs.

The Tandem X2 cartridge is different, but easy once familiar with steps. Maybe just a couple minutes longer than MedT fill. Basically 1 extra step to first fill syringe, then transfer that to cartridge.

The auto mode has worked well for me, and have kept A1C in mid 5s, using sleep mode 24x7.

The auto bolus doesn’t kick in until approaching 180, so I rarely see that. (it may be disabled in sleep mode??).

There is a android app that simulates pump screens and operation. May be one for Ios too.

T:Simulator App


switched to tandem form MedT 770g. For the pump itself, I notice almost no difference. Yes the refills are more cumbersome. but as far as yanking sites? I have used it for almost one year with no differences noted.

For the pump alone, I think it is dealers choice. I do like the medt pump a little better. What causes me to suggest Medt is the fill process. but frankly the tandem fill process is not bad overall.

I think the pumps are an even coin flip

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How would you compare the associated CGM in auto mode. What ranges does Medtronic pump target? Is it user driven?

Would you compare Medtronic cgm equal to dexcom?

Another year and I will have oow pump and starting MC, which I believe is a 5 year pump commitment.

Edit to add:

Link to pump review/comparison by Gary Scheiner

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Control-IQ doesn’t give auto boluses in sleep mode. It raises your basal rate to bring you back into range and does a pretty good job. You can still give correction boluses manually.

The t-slim is my first pump but I don’t find the refill process to be difficult. The only part I ever have trouble with is the “soft spot” in the cartridge that you insert the needle into isn’t always perfectly centered so it can take a couple of tries to get the needle where the plunger will depress easily.

Other than that I love the pump and Control-IQ has made a big difference to my quality of life. There isn’t really any learning the pump needs to do. You set your basal rate and the pump will use your numbers to make it’s adjustments. Your basal requirements may be slightly different than with Medtronic but you should be able to tweak that within a few days.


Wasn’t addressed to me but I’ll answer anyway. At first I thought they were roughly equivalent accuracy wise, but over weeks of use I realized the Medt Guardian was having a really rough time picking up on my pronounced Dawn Phenomenon—the thing that put me on a pump to begin with. A bad shortfall, because it meant I was always starting the day with a much higher fasting BG than the auto-mode was capable of dealing with adequately—too slow and non-aggressive, so my number going into lunch time was always higher than I wanted and blousing never seemed to catch up unless I went zero-carb or overstated what I was eating to trick the pump into being more aggressive. The daily calibration requirement is also ill-suited for pumping, not just the required ones but also the ones from some glitch, perceived or real, in your BG track that it was glitching on or whatever. Not to mention the elaborate business of getting it taped on correctly. Whole thing just felt very kludgy by comparison with Dexcom, which I’d been using for years before switching. IMO if Medt had half a brain they would have long ago opened up to integration with Dexcom and dropped the attempt to create a locked-in ecology with their homegrown CGM. It’s just not their wheelhouse.


Using a t:slim in sleep mode 24x7 in an attempt to meet a more aggressive target will be counterproductive , unless you are so skilled in using an insulin pump and doing manual corrections that you don’t need a pump with automatic mode.

Unless you are already in target range +75% of the time, AND a high enough basal rate during each period of the day, sleep mode will be relatively ineffective at reducing blood glucose “overnight.”

What you would be doing by using an HCL pump in the automatic activity mode optimized for when you are not eating and inactive is creating a situation where you would have to do more work because you would be distrusting what the pump can do.

HCL insulin pumps are the first step along the road to making life as an insulin dependent person with diabetes easier. Having lived with it for 45 years I know how stressful it can be to constantly worry about going high or low, having to balance higher BG as a safety margin against hypo, against the certainty of more complications. That stress increased during my life as those complications manifested to the point where I was questioning every decision I made about what could do.

When I first started using a Tandem pump my only concern was nocturnal hypoglycemia. I had been using a G6 CGM for a month previous to that, and had accomplished very good time and range and A1c using MDI with Novolins. So I initially opted for a Tandem pump with Basal IQ - essentially Sleep Mode on demand.

The results I got from it were not much better than what I had been getting manually, and the amount of time and effort that I was putting into trying to manage my daytime BG increased.

As I was doing this I was reading clinical trial reports of the use of Control IQ by PWT1D including those with the hardest to manage BG- children. Every group studied got better time in range, lower average blood glucose. The group that benefited the least in A1c were those who already had the lowest. But every group experienced lower deviation.

I’ve never liked the A1C test because it’s a broken clock metric. When I had my lowest A1c’s I was experiencing my highest rate of hypos and highs - when my control was the worst. So I upgraded to Control IQ. For about a month after that I continue to spend almost as much time and effort as before but my results improved . Over the next few months I started to trust the Control IQ algorithm more, made fewer corrections, second guest and micromanaged the pump less - and my results improved significantly.

My feeling is that getting 97% time in range, a daily average BG below one of the diagnostic criteria for diabetes, with a statistical variation under 20%, with no more effort than using a BGM (and fewer surprises) before meals is worth it. I’m sleeping better now than I have in 40 years and I’m confident that month after month I can maintain this level of control.

Only you can decide how much continued time and effort, how much stress, is worth an improvement in blood glucose control. My suggestion is that it would more productive for you to use the information from your CGM to monitor the effect of your lifestyle and cautiously modify it than would be to second-guess Control-IQ.

As far as the finicky cartridge change" goes, i have peripheral neuropathy and it takes me under 10 minutes from start to finish, including prep and clean up, to fill and change the cartridge and infusion site. There’s less precision required than doing MDI 4x daily, the time and effort seems slightly less. I haven’t had a problem with cartridges, with infusion sets since I changed to TruSteel. My problems have been with sensor sites and less so with infusion sites.


I never usedMedtonic - never wanted to. Anyway, I love my tANDEM x2 - BUT i USE biq. mY ARNING IS TO PERHAPS TRY biq FIRST. iF THAT MEETS YOUR NEEDS SUPER! yOU CAN’T GO BACK FROM ciq TO biq. i AM VERY AGGRESIVE IN MY t1d MANAGEMENT AND THE ciq TARGET OF 110 IS TOO HIGH FOR ME. i LIKE TO HAVE MY FOOT ON THE ACCELERATOR. BRAKE AND CLUTCH IN MY t1d CAR. Oops, hit the caps, key no time to retype. Anyway, My A1C’s are consistently in the 5.3-5.5 range, my TIR is in the 90+%. With BIQ I am in charge of the bolus dosages - I can take in the trend arrows, I can look at my bolus history to see if I have “food on Board”.
Re: your question on infusion sets. I prefer the TruSteel. It is a two part set with a “business or infusion [part” and an anchor piece. If by chance (very very rare) I pull out the set, I can just pop it back in and use a bandaid (or once a piece of masking tape - I was at a hardware store) to secure until I want to deal with changing the set out.

Another reply. I love the fact that my Dexcom G6 CGM is integated with my pump. I only have one device - and it is attached. I have absolutely no interest in using my phone to bolus (although I guess you can) When I was still working, I was on call 24/7 By the time smart phones became consumer products I was “over them”. In fact, it is the fact that with Tandem I don’t need to carry a device like you do with Omnipod.

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Tidepool was going to do this, but don’t think it was actually completed. (2019)

“Tidepool and Medtronic will together demonstrate the power of interoperability. In an era of empowered health consumers, this collaboration opens up new opportunities for people with diabetes to choose the technology that’s right for them.”

Hasn’t happened yet…

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For me the change in A1C has been minor. With Tandem my A1C went up 2/10. Now the difference is that I am less actively engaged with the tandem than the MedT. In terms of ease of use, it depends. I am a very engaged used with MedT. I let it flow with less interference with Tandem.

I am happy with choice to use Tandem and I will not be opposed to going back to MedT. I left Medt for three reasons.

  1. I wanted my BS on a watch,
  2. I wanted the upgrades associated with the 780g, including the guardian G4 transmitter,
  3. I wanted downloadable pump software.

One year ago, Medt was just starting the improvement plan and it seemed unlikely to come out anytime soon.

I believe the 780 will be a big upgrade for Medt given the European experience. As I say at the end of the current five years I will definitely consider going back.


Yeah, I remember getting excited when that press release came out, but since then, crickets.

Some of the comments were pretty skeptical whether Mt was acting in good faith…

I’ve been on the Animas pump (loved it), the Medtronic 630 (I think?) and now the Tandem T:slim. I like it, but it’s not a panacea for me. My endo told me last month that in Canada, Medtronic is doing research trials for infusion sets that you can wear for 10 days and are working on improving their sensors. He asked me if I wanted to be part of the study, but it’s too far away for me to commute-- rush hour traffic through Toronto, no thanks! Anyway, I think that if their 10 day infusion set becomes a reality and their sensors are improved, then in 4 years, when I’m entitled to a new pump, I just may switch back. Tandem’s horrible case and clip drive me crazy. I’ve tried other cases and clips, and have found the phone clip and silicone case work best for me, but I still don’t like it that much.

You wouldn’t have to change your cartridge in that circumstance. You could just change your infusion set and fill the tubing.

That said, filling the cartridge isn’t hard. The only (slight) stress point to me is being sure that I’ve gotten all the bubbles out of the syringe, but that was the same with the Animas (my previous pump) and I assume with Medtronic, too? Prefilled cartridges would be nice, but I think that insulin is meant to be stored in glass.

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I “sleepwalk” (use Sleep Mode during waking hours) occasionally but not that often. The idea is that you’re lowering the threshold for when the pump starts reacting to a higher blood glucose reading. I think it works nicely if your blood sugar tends to be relatively stable (like if you don’t eat many carbs). The downside is that in sleep mode Control-IQ won’t act aggressively if your blood sugar starts rising rapidly. It will react by raising your basal – and if you already have your basal doing most of the “work” of controlling your blood sugar that might be enough – but it won’t give you a big bolus to bring things down. You can give yourself a big bolus any time you want, of course.
You can always change settings for your basal and for insulin sensitivity to have a more aggressive Control-IQ. Some people can apparently tinker with it so that they run consistently in the 70s or 80s but doing that you’re definitely working against the system which wants you a bit higher than that for safety.

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I’d be happy to stay 90-120, which is about how I am now.

I just switched to Tandem/Dexcom after using Medtronic for 18 years. I had multiple Medtronic Paradigm models (715, 722, Revel & 530g). The original SofSensors that worked with the x22 & Revel models worked well for me. When I moved to the 530g/Enlite sensors I had horrible results. The sensors read low, all the time, every one of them. I gave up using a CGM because they were worthless and that’s all my insurance at the time covered. When the 530g died I let Medtronic talk me into getting the 670g with the Guardian sensors. The sensors worked well for me but I hated auto mode on the pump. It kept me too high all the time so I stayed in manual mode. I upgraded to the 70g because they promised the 780 was coming very soon but that never happened. It was basically the same as the 670 except the transmitter was bluetooth and you could view your readings on a phone. Again I tried and rejected auto mode.

I’ve been using the Tandem t:slim X2 and Dexcom sensors for just over 2 weeks so my experience is limited. It is so nice not being forced to do calibrations every day. Changing every 10 days vs every 7 is also nice. The pump is smaller than Medtronic (the 670/770 models) but comes with a horrible case/clip. Every other one I’ve looked at adds a lot of bulk. I always wore my Medtronic pumps clipped inside the front pocket of my pants but Tandem has to be worn with the screen facing out so I can’t do that. I’m dealing with it, it’s not a huge problem.

I was worried about the cartridge fill process but it really isn’t an issue. A couple of extra steps but it doesn’t take a long time. Medtronic definitely wins when it comes to infusion sets. Tandem has two angled sets similar to the Silhouette. One is manually inserted, the other comes within a disposable inserter. They have the steel set that’s the same as the Sure-T. THey have two 90 degree soft cannula sets that look identical to the original Mio. I was sent the Autosoft 90 with my initial order and it is exactly how I remember the Mios to be. I hate the connection at the site, it is tough getting it unhooked sometimes. I’ve already requested a switch to the Autosoft XC for my next order. I think it’s the same, only the clip at the site is different. Sadly, they don’t have anything like the Mio Advanced which is what I had been using for the last year+ on Medtronic. They also don’t have anything like the Quick-Set.

My original settings from Medtronic do not work in the Tandem and I was running high with Control IQ. I’ve tried Sleep Mode 24/7 but kept going high overnight. It does not give you an auto correction in sleep mode but the basal does adjust, just not enough. Just a few hours ago I created a new, much more aggressive profile that would probably kill me if I used it without Control IQ, to see how that would work. I have been running high at the times where I had a tendency to be low on Medtronic so it’s frustrating. My insulin use has gone up, and not just the waste caused by the tubing/cartridge. My TDD has increased.

I’m hoping that I can figure out what settings needs to be changed to make Control IQ work better for me. I did well in manual mode with Medtronic but would really like to not have to micromanage everything myself which is why I switched to Tandem. Part of it is also that I hate higher numbers, I like 160 as my high cutoff. If a pump kept me at 150+ all day it would drive me mad.


Is that because of the touch screen? I never used the clip with Medtronic, just stuck it in my pants or shirt pocket, and I was assuming I’d do the same with the Tandem.

The frustrating months-long struggle to get the 670 to be aggressive enough is still a traumatic memory. I really don’t want to go through all that again. Basically why I’ve been clinging to my old 723 like grim death. But the software going flakey is forcing the issue. Need to resolve this before the next battery change leaves me with a dead pump!

Same here! It does seem that Tandem at least offers more choices of things you can tweak. With the 670 there was only one setting that really made any difference—insulin duration—and even that was hard-limited. Hope you’ll come back to report on how your more aggressive profile worked and what you adjusted.

I wear my Tandem X2 in front pocket, with screen facing in.

I have an old pager case (before cell phones), that actually is perfect size. Used with my Medtronic 523 for many years, now with Tandem X2.

I occasionally use the Tandem app on cell phone, but still dose from pump. Xdrip is main display for cgm.

It’s because the pump can lose connection with the Dexcom if the screen is facing your body. The blue tooth in the pump is behind the screen.