Medtronic 780G vs. Tandem T-Slim

I’ve been on the Tandem T-slim with Ctrl-IQ for over four years. Before that I was on Medtronic pumps for over ten years. Like many others, I tried the 670G with the first Medtronic CGM and it practically gave me a nervous breakdown. A friend of mine was the clinical director at Tandem at the time and convinced me to try the T-Slim. I love the Dexcom G6, mostly. The Tandem pump itself, not so much. I have pretty decent control; GMI 6.3; AVG BG 124; TIR 93%. But, man, do I have to work hard for those numbers. So I switched to the Medtronic 780G. How do I prefer the 780G? Let me count the ways.

  1. The Tandem has so many settings. Trying to get them all “dialed in” for success has been a constant battle for me. The 780G has a completely different algorithm that doesn’t depend on many settings at all. That’s a topic unto itself for later.
  2. I could never see the Tandem screen in sunlight. 780G is much easier to see in sunlight.
  3. The T-slim doesn’t have the square bolus feature. I forogt how much I missed that.
  4. The T-slim touch screen is so darn sensitive. I was always inadvertently requesting a bolus as I was replacing the pump in its case. The 780G goes off automatically in 15 seconds (changeable time duration) and the buttons are not sensitive in the same way.
  5. Way less waste with the 780G. Both insulin and plastic.
  6. Way faster and easier to change the reservoir/cartridge. My vision is deteriorating a bit and it got harder and harder to see the little white dot.
  7. Personally, I prefer to change out the battery every couple of weeks, or as needed. I hated being tethered to charging my pump with a cable. I just bought a 20-pack of good AA batteries for $19. I;m happy with that.
  8. Medtronic’s new extended infusion sets are great! A week on one set, no occlusions!
  9. You can change both the reservoir and infusion set weekly, or change just the reservoir, or just the infusion set. Choices! And less waste.
  10. The 780G has a great “Review Settings” screen where you can review ALL your settings. Very convenient.
  11. You can decide on the bolus speed with the 780G. Again, nice to have choices.
  12. It comes with a sturdy clip!
  13. The pièce de résistance: the user sets the BG target: 100, 110 0r 120.

well, there you have my list. I’m pretty happy. The Guardian 4 (and the algorithm for the 780G merit separate discussions.


Thanks for all that detail! It’s very helpful. Please keep us posted as you gather more weeks and months of experience with the Medtronic.


Thanks re the 780G. I would love to read your Guardian 4 review soonest.


Thanks for the lengthy description! I went through users’ claims about the Tandem and Medtronic pumps several years ago, and the strong majority were favorable to the Tandem. Partly (but not entirely) on the basis of those, I switched, and found I did like the t-slim (and who names these things?!) better myself. But it’s always good to get both sides of a decision like that from someone who has done both, and I appreciate your contribution. Always good to be aware of all sides of an issue!


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Hi Keith, I totally agree - we all have personal preferences and needs. Note that, several years ago when you researched users’ claims about the two companies, the Medtronic 780G with its novel algorithm did not exist (nor did extended infusion sets, or choices for BG target, etc.). I had become kind of obsessed with all the setting on the T-Slim, and chose the 780G in large part because of the promise of less work with the different algorithm. Once I got the 780G, I realized all these things I preferred about the Medtronic pump, so I wanted to lay it all out there. I know lots of people are wondering about the pros and cons, and it is really such a personal decision; I’m sure many will still prefer the T-Slim. Lucky us - those of us who have choices!


The tslim DOES have the square bolus feature and unlike Medtronic, it can be used while the algorithm is running. There is a max 2 hour limit. I do what Medtronic calls Dual Wave all the time, some up front, the rest extended. In order to use that feature on Medtronic you have to exit out of Smart Guard.


Thanks for mentioning this, I used it many times in my first year of Tandem X2, but then got lazy with the extra step. Will try using it again.

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That is sooooo helpful! Thank you!

I’m on Dexcom, G7 as of this summer, and need to upgrade my pump in next few months. Had the Medtronics CGM years ago, just useless & frustrating. Dex G6 lost the sensor signal regularly, or fell off, or… But when it worked, it was accurate.

I made inquiries about pumps on this forum a couple of months ago, and there seemed to be lots of support for Tandem. While it would be nice to eventually get to 1 device, perhaps even allowing the device to make some “decisions”, i watched a number of videos about Tandem yesterday and came away nervous about what i saw. Your notes will be a big help as i continue to evaluate. Again, thank you!

I’ve just reviewed some Guardian and sensera youtubes. The sensera will not talk to pumps, and its the Medtronic next cgm. Though another is to come later that will. All in ones vs the Guardians. So now I am thinking of the Medtronic 790G (780?) and the Dex G7. I really need to control of the hookup but I am really tired of the Tandem’s quirks. Warnings that I had a high BG 3 hours ago and that the infusion set has been in for 3 days, etc etc and the hassle with the cartridge change. The thought of a two-part Guardian cgm is a no go. Plus in one youtube it said its MARD accuracy was in the 10s vs the 7s for Dex, with lower being better. Here is the link if interested.

The easy use of the Medtronic pump is attractive and the accuracy of the Dex is as well. Unfortunately, they don’t hookup together.


Sorry, I did not know it would create a big icon thing like that in my message. How do you enter a link without it doing that?

No worries! Great for those of us with poor eyesight! :slight_smile: I don’t know how accurate all the youtube videos are, but you should always try to confirm what you see or hear. The Guardian 4 has a higher MARD (so not as accurate) than the Dexcom, but not as different as what you quoted. all the medical websites and the research sites state that the difference in MARD between the two are not different enough to be used as criteria for choosing one over the other. I wish Medtronic pumps talked to Dexcom CGMs, but, alas, they don’t. I so prefer the 780G pump over the Tandem T-Slim that I am willing to put up with the Guardian 4 until the “Simplera” and the “Instinct” are available. (The Instinct is basically Simplera that integrates with the Medtronic pump; the company says the Instinct will be available in the U.S. in 6-9 months.) The Simplera has been approved for use in Europe, so I will be watching the European forums for user feedback.

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@Cevans54 Well, my age has me concerned about “waits” for US entry for these new versions. I am glad to hear that the Instinct may be that close to the Simplera but then I am not sure that the Simplera is available yet… not that I would want it.
The Dex has always been perfect for me in accuracy --within very few points of my meter almost all the time. So anything less would trouble me. Weird names for their cgms! Thanks much for your quick response and info.

You can turn off most of the Tandem alarms. The alarm for three days is in the process of inserting a new infusion set. Next time you are changing your site on the screen where you click to fill the tubing there is the set change reminder. Just click on it to turn it off.


Good if the algorithm is smart enough to figure out and predict basil needs (i.e dawn phenomenon).

I liked Tandem because I could manually set my base basil, and Tandemn would adjust only if needed. So less reliance on a “algorithm” that may or may not work for you.


@Cevans54 ,
After much research and reading reviews from users around the globe, I’ve ordered Medtronic 780g and G4 transmitter. My 670 is out of warranty. Hopefully, it’ll help me get to 80-95% TIR that so many others are reporting.


Good luck! I will post how I’m doing with the 670G in a couple of months. Keep us posted on your progress, too. These are not easy decisions. I wish the pump companies were compelled to allow us to try out their pump for 30 days upon request.

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@Cevans54, I think there is some sort of provision for return like that with Medtronic. I’ll have to look into it. If I can actually get the 780. I lime the 670, but I need more and mine is out of warranty.

I just found out this morning that Medtronic has a 90-day return policy! I don’t know what Tandem has. Do you have a rep? I never had a rep with Tandem, and my training was mediocre. I got trained on the mechanics of the pump, but nothing on the hard stuff. It didn’t occur to me that my endo might have someone skilled in the algorithm and ramifications to all the settings to get it properly “dialed in.” I have gotten so much great advice from folks in this forum and my endo, but it is just too much work to get it right for me. My endo thinks my numbers are great, so that’s not the issue. It just takes up too much of my life. Anyway, my original point was that I have really appreciated working with the local Medtronic rep who knows all the endos in town, and can swing by the house (as he did) with a spare infusion set. I’m sure Tandem has reps too, I just never heard about any.

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I too would be very interested in learning about your experiences with the G4 sensors. The only reason I chose the Tandem over the Medtronic was because I hated Medtronic sensors and calibrating them and I really liked Dexcom.

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I’m not surprised that someone didn’t learn how to use the t:slim effectively, how to determine the settings and set them once. I’ve seen lots of VCRs, ovens, cars with the wrong time flashing on their clock displays.

It’s a pity that you had to spend all your time constantly fiddling with settings that could have been roughly estimated in a few weeks, and refined once a month if you had learned how to interpret the data uploaded to Tandems site. It’s shameful that no one taught you how to use CGM data to tweak your lifestyle, or how to use it to systematically determine the pump settings.

I don’t blame you for that. The education we receive on using these pumps is awful. I received none.Luckily for me I didn’t expect any.

I’ve never had a teacher train me to use “tech”, especially diabetes tech, since I was first prescribed 26 units of beef NPH once a day and to eat less carbs if the tape I peed on turned dark.

I knew that if the FDA had approved equipment for home use and Medicare covered it as durable equipment, then there was a printed owners manual - and I knew how to read a manual even if it was badly written. To my surprise Dexcom and Tandem have very well written manuals.

Dexcom’s manual only assumes that the reader recognises that there’s a reaction of glucose to everything you do and feel and you can figure out what to do with that information just as you would with a BGM. “It ain’t rocket science”. I ordered the Dexcom manual and read it before using the G6,

Tandem’s manual explains what every setting and button does. All it assumes is the reader understands basic insulin management terms and principles. Tandem incorporated the entire Dexcom manual in the Basal-IQ and Control-IQ manuals, which I downloaded and now have in my phone and laptop .

I spent a day reading the manuals and making post-it notes with questions I had before I took the laughably terse online tutorial. I thought it was a good investment of my time to learn everything I could about a machine that would be attached to me for 5 years.

I was surprised and disappointed to find that a $5000 “smart” pump had fewer settings than my non-tech wife knows how to adjust on her phone, and more warnings than an arc welder. It’s just a scientific memory calculator with a single sensor feedback loop, a few more memory registers, a schedule that loads them and a precision pump it controls.

None of my usage questions were answered in the manual or tutorial. I figured them all out within a few weeks, helped by another book Think like a Pancreas, borrowed from my library.

I see differences between the Medtronics and Tandem pumps but only one of significance.

  1. The Tandem isn’t complex to set up. It has only 5 required settings: weight, approximate units/day, CF ICR, basal rate. Sleep schedule and detailed profile are optional, as are the alarm settings. Weight and TDD aren’t used after the Control-IQ algorithm has run for a day - unless you change them.
  2. I’ve never needed to read my pump screen in the direct sunlight. I have two hands and could shade it if I had to. I know the basic bolus menu well enough that I don’t need to read the software buttons. My phone screen continuously displays the glucose reading, a graph and 24 hour rolling metrics. I can read it in direct sunlight.
  3. The t:slim does have the square bolus feature. It’s called Extended bolus. Set the initial bolus to zero and during the interval chosen it will deliver a constant flow. It’s linked to the bolus calculator and the feature is shown every time you give a bolus.
  4. Extended bolus can also be used to adjust bolus delivery speed. Set the initial bolus to zerom the duration to a one or more minutes.

I know that few people have the patience to read a 175 page (350 half -pages) manual in one day, but not to do it in 1461 days?

  1. The touch screen is not as sensitive as my phone, tablet or laptop. The touchscreen "buttons are smaller.
  2. “Way less” isn’t a number. Waste as a percentage depends on fill and use.
  3. It normally takes me about 5 minutes to fill a new reservoir, (less if I fill 2 or 3 cartridge at once) 3 minutes to swap one out and have the pump fill the infusion set. A $20 fixture is available on Amazon to hold the cartridge and syringe in perfect alignment for filling.
  4. I have a flat LiIon 5000mah battery bank ($12) with a retractable cable ($1.25) that I carry in my emergency/backup kit. I can charge my pump while wearing it.
  5. The Medtronics infusion set cannula - IF it lasts longer in my body would save me about 10 minutes per week changing infusion sets.
  6. I’d need to have a lower TDD and for the cannula to work for 5 days for the choice of whether to change the reservoir, infusion set or both to be an advantage.
  7. I know what my pumps’ settings are. (I determined them by delaying one meal a day, eating a controlled diet and calculating the results.) The only person who reviews them is my endo, (who barely understands how Control-IQ works) and they get them from a Tandem report I made available to them.
  8. I have a nice silicone case that protects 60% of the pump front and most of the sides and back, with a stainless steel belt clip - $15 total.
  9. The bolus calculation/control target has no significance. My level and trend are important. I don’t care that my A1C is around 5.2. I care about my 24 hour TIR, average and SD each day - stats which none of the currently available pumps directly provide.
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