Tandem T.Slim X2 or Minimed 780G AID

Need help to decide.
I have had a insulin pump for 31 years, and tried everything from H-tron to Tandem, Minimed, Animas and what all the others has been called.

Today I use Tandem T-Slim X2 with Dexcom G6 CGM (not Control-IQ but Basal-IQ) and the warrenty is out so I cant upgrade it to Control-IQ.
I should change this now so I can have with complet AID function and I can choose between T_Slim x2 and 780G.

I know the drawbacks with the T-Slim since I used it for years and I can say that some of them are

  1. The screen sensitivity that drives you crazy sometimes. Some jeans has a pocket material that always mimic a finger,
  2. Refilling don’t have to say more, the subject has ben up many times here already.
  3. The pump only connects to CGM sensor with Bluetooth, not the mobile.
    4.The Dexcom CGM that don’t tell you when the transmitter is the last time you can use if you have it connected both to mobile and t-Slim x2.
  4. Lifetime of the Dexcom transmitter (90 days or max 112)
  5. the connection between the reservoar and the infusion set is like 10 cm out from the reservoar and tend to get stuck in many clothes.
    7.If you touch the screen to lock it locks so when you entering like 30 calories the 0 is very often mistaken as a lock screen command
  6. The battery lifetime of a charge when using with CGM is about 4 days and from 20% down to 0% it goes very fast

So why do I consider changing to Minimed 780G?
780G have adjust every 5 minutes, Control IQ one every hour (according to specs)
788G has three values that it should aim for (5.5, 6.1 or 6.7) Control IQ has only 6.2 as goal. According to my doctor I should have my goal set as 5.5
780G sends all information to my mobile, not only the CGM values, so you can share your doses as well
Standard battery

My nurse says that they have very good experience with 780G and has been using it since november last year. The Control IQ is just used since February so there is no real data in yet at my hospital.
They also told me that the 780G CGM should be fingerstick free this autumn.

I know I just have written the bad things about T-Slim X2 and only good things about the 780G. Just let me say that the Tandem t-Slim X" is a excellent insulin pump and it works very good with the Basal-IQ and have stopped so many low values for me. But the Control IQ as it is just now proberbly to slow and with only one aim value (6.2) it might be so that the 780G is better for me.

Watchfaces for android watches, is there any for minimed app? Dexcom has one(not briliant but it works and I use it a lot to quickly see my values)

What are your input on this?

hello @tellblom Martin, welcome to the forum! I am sorry I don’t have much to add, I am loking forward to reading responses and to your decision and hopefully, an update!

The heart of the matter is the CGM. most of the complaints I have heard revolve around the Medtronic CGM, in the general form of accuracy, reliability, and all of the mandatory and problematic calibrations currently required. I have had decent success with my Medtronic CGM, but I am compulsive in the way I calibrate it and I acknowledge that an error or even a deviation in the timing or the method to calibrate the CGM to be the weakest part of the Medtronic system.

so do you have “Great Results” with the Medtronic CGM? if YES then that is a major factor to the Medtronic v T-Slim question.

also I would advise to not base the timing of the decision around the new Medtronic CGM or the phase in of the new Dex 7 ot phase out of the G6 by Dexcom, the timing of these events are not clear.

Good luck and I hope you find the forum and conversation useful.

Thanks Joe,
One thing that I never seen discussed is that the Dexcom G6 also has sensors that are way of but often not noticeable since you don’t take the test in the finger because you shouln’t have to.
I have sensors that has shown values that are up to 2.0 wrong (i.e the CGM says 5.4 and the actual test with 3 separate blood test shows between 6.9 and 7.4). Mostly they are quite the same as the fingertest.

I’m just saying that many think that they are so accurate because they never take the fingertest anymore. I started to test at least once per sensor after it has been in set a couple of days after I had a very low (2.3) and the CGM said 4.5.

My hospital also says that the HBA1C values from the CGM can be a bit of comparing to the values uploaded from the CGM system (using diasend).

I think both systems has it ups and downs the question what downs are easier to live with.

One of my downs that I will have a big problem with is that 780G does not have a watchface for android watches, and that could be de deal breaker for me.

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I use the Medtonic 670g pump and CGM system and will undoubtedly upgrade to the 780 system sometime this year. I know people speaks negatively about the Medtronic CGM system, but it works great for me. Do I calibrate 3 times a day? Yes and that’s probably why it works the way it’s intended. Follow directions and things usually work out ok :slight_smile:

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Thanks for the input. I used G6 for almost 2 years and I know the drawbacks with that.

You calibrate 3 times a day? What I understood you can miss one calibration without the pump going crazy. How do you choose the calibration times?

The guardian CGM requires calibrating every 12 hours and I add a third one to keep things running smoothly. I calibrate when I wake up and go to bed. My third one is usually between 2 and 4 in the afternoon.


Hi, may I pls mention just a couple of items that you may like to verify, as you work towards a decision. I am not arguing for either side.

You mentioned that Control IQ adjusts once per hour, while 780G adjusts every 5 minutes. You may like to check this spec. Control IQ recalculates basal flow rates many times per hour. It’s possible you are mix-and-matching basal flow rates with Control IQ boluses. CIQ boluses are limited to once per hour but I think you will find that CIQ tinkers with the basal flow much more frequently than once per hour.

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I use the Tandem T.Slim X2 with Control IQ and use the Basal IQ before that. My previous pump was the Animas Vibe. As for some of the drawbacks, I have made good progress with filling and have good tips. A lot of the other drawbacks you mention are related to the Dexcom G6. I love my G6, I moved up to it from the G4 and the insertion process is much easier and the sensors last longer. While you get 10 days, I can often get 20 days. I do still check with finger sticks and it is always pretty close, sometimes scary close! I can go about a week on a battery charge using the CGM and CIQ, and since it’s a micro USB charger, it’s not a problem. I hope they upgrade to USB 3.0 soon, though. I use the Dexcom App on my phone as the primary and it works will with the X2, I’ve never noted any issues there. I think the new Tandem app also connects to your phone to let you visualize what is going on, but not control the pump just yet.

When I switching from BIQ to CIQ, my lows almost disappeared. The new software does a better job of predicting and lowering the basal rate while I’m dropping so I have hit those hard lows. I’m an active person, so I would routinely get lows, but now I’m below 70 about 3% of the time which is great. I do still struggle with highs as BIQ doesn’t quite seem to catch up to my eating quick enough, so I need to do better with bumping up my rate after a hard workout.

All said, I’ve been very happy with my X2!


I just switched from Medtronic 670g to Tandem t:slim x2 last week after using the 670g for a year and a half. What I’ve noticed so far:

Dexcom G6 is far more accurate than Medtronic Guardian 3. Guardian 3, as noted above, needs to be calibrated at least every 12 hours. More often if the algorithm in any way suspects that something may be off. Blood sugar readings changing rapidly? Calibration alarm. Blood sugar readings been too stable? Calibration alarm. The thing woke me up almost every night, even after I turned off most of the alarms. I’ve had a Dexcom in me for two weeks now. (I inserted my second sensor a couple of days ago.) The first day it was off (which has frequently happened to me with the Guardian 3), but after that it’s been spot on, even without calibration.

I do find the touchscreen annoying, but it works. And I’m told that a software update allowing you to control the pump from your mobile app is undergoing FDA clearance right now.

Speaking of which: You can’t use a Dexcom receiver and the pump at the same time. But you can use the pump, the Dexcom mobile app, and the Tandem t:connect mobile app all at the same time and get current readings in all three places.

I do like the Medtronic reservoir filling system better than the Tandem, but it’s only every 3 days and not that big a deal. Likewise, the Dexcom generates a lot more plastic waste than the Guardian insertion process, but I’ll take the improved sensor accuracy and lifetime (10 days rather than 7) and the lack of finger sticks.

Medtronic has a replacable AA battery. I bought rechargeable batteries and just changed it once a week with a fresh battery. But the battery cap did break, which is dangerous. And the Tandem pump recharges fairly quickly. Just plug it in when you’re sitting still near an outlet for a while. Or when you’ve disconnected the pump so you can take a shower. Not a problem.

You asked about the Control IQ vs Medtronic algorithm. Control IQ has been better at keeping my blood sugar in range so far. Both pumps adjust your basal rate every 5 minutes. But if you’re running high and need more than the basal rate, Medtronic requires you to do a calibration so it can be sure it’s giving you the right dosage. T:slim has faith in the Dexcom and will let you bolus directly off your CGM readings. The once per hour thing you read is additional. T:slim will adjust your basal rate, giving you extra insulin every 5 minutes. But, on top of that, if you’re still running high, you can either have it give you a correction bolus at any time (it will subtract out your “insulin on board” value) or, if it’s been an hour since your last bolus, it will automatically give you a bolus of 60% of the manual correction (and then allow basal insulin to make up for the rest, just to ensure it doesn’t overcorrect).

T:slim does have two additional modes. Sleep mode has a tighter blood sugar range, so it’ll be more aggressive about adjusting the basal rate to keep your sugar down, but it won’t do the automatic correction bolus. I wish it would. I was up last night precisely because my dinner was digesting slowly and I ended up going over 250 in the middle of the night despite being on the low side at bedtime. But I had that happen with the 670g, too. In fact, I had the same exact dinner my last night on the 670g and my first night on the T:slim, and while I went high both nights due to the high amount of protein, the t:slim kept me in better range on its own and did not wake me with an alarm. Exercise mode raises the target range so you won’t go low from having burned calories. You can turn both modes on and off at will (though not at the same time, of course). Some people keep sleep mode on 24/7. Some don’t use it at all. You can talk to your doctor and see what works for you. Permanent sleep mode could potentially get you closer to your A1C goal.

One thing that does concern me about the T:slim is the temperature sensor. (Which Medtronic doesn’t have.) If the temperature of the insulin cartridge reads over 98.6 F, insulin delivery immediately and completely stops. It’s not just an alarm warning you that your insulin has gotten too warm and you need to take care of it and keep an eye on your blood sugar. It’s a shutdown of all insulin delivery. I asked my trainer about that. What if I’m in Arizona and it’s 102 F outside? She said as long as you keep the pump out of direct sunlight (in your pocket or a bag or something) it should be okay. But if it’s 99 in the shade, you’re screwed.

I should note that Medtronic and Tandem have different calculations for how much insulin is in your system. The 670g doesn’t count basal insulin. Its “active insulin” counts bolus insulin and then gradually counts down as that wears off. The T:slim’s “insulin on board” counts basal insulin in your system as well as bolus and deducts that total from bolus calculations. Because of the way the algorithm works, you can even end up with a negative value for “insulin on board.” The Tandem way of counting is designed to prevent you from overcorrecting with your bolus while also being more accurate in its own dosing.

Tandem won’t let you mute volumes. You can set individual things like alerts and touchscreen presses to “high,” “medium,” “low,” or “vibrate,” but you can’t turn them off completely. So every single time you press the screen, it will either beep or vibrate and there’s nothing you can do about it. Medtronic makes you unlock the pump screen to guard against accidental presses from bumping into things, but it only makes noise when there’s an alarm, and you can set most of those to vibrate.

All in all, so far the t:slim x2 has been a significant improvement for me over the 670g. The 770g is the same as the 670g, except that it can pair with your phone.

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I guess I can sum things up this way:

The Medtronic algorithm is designed around the fundamental assumption that you cannot trust your CGM. It adjusts basal rate based on CGM readings, and that’s it. You can’t bolus off it. You have to calibrate at least every 12 hours (and more on the first day of a new sensor). If you want your bolus to factor in your sugar level, you have to enter a BG value. (You can manually enter the CGM reading as your BG and just not calibrate, but you’re not supposed to do that. I did that sometimes if I was high between meals. Give it the CGM value as my BG, tell it to bolus, and then calibrate before the next meal to make sure things were on track.) If anything looks weird with your CGM readings (they’re fluctuating too much, they’re not fluctuating enough, they’re too high, they’re too low, etc etc) the pump will sound an alarm and ask you to calibrate. At that point, the blue Auto Mode shield turns grey to signify that the pump is in “safe basal” mode, where it stops using the CGM values to adjust basal and just gives you a steady backup rate until you calibrate. If you don’t calibrate within 2 hours, it kicks you out of auto mode entirely until you do. (Very rarely, during that two hour window, your blood sugar trend line will change enough that it will accept things and the shield will turn blue again.)

The Tandem algorithm is the complete opposite. You never have to calibrate it unless you have reason to believe it’s wrong. I still calibrate mine at least daily, but my endo said she has patients who calibrate once a week, and they’re fine. So the Tandem pump is built to use that CGM reading all the time. It adjusts your basal, same as the Medtronic. But if you put in a food bolus, it automatically factors in your CGM value to increase or decrease the bolus amount (unless you tell it not to do that this time). If you leave it running without touching it, it will automatically give you a correction bolus up to once an hour. If you get a high sugar alert, the first thing the pump does is ask you if you want it to give you a correction bolus, and it calculates that based on the CGM.

For one thing, this tells you something about the difference in accuracy between the Guardian sensors and the Dexcom. But it also tells you a lot about daily usage.

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Thank you for the great input.

As it is right now I’m leaning on continuing to use the T-Slim x2 and order a new upgraded X2 (the one I have is out of warranty and can’t be upgraded with Control-IQ).

Hi @WearsHats and thank you for your concise descriptions and comparisons of the pumps/CGMS. I’m in the DMV, which gets hazy, hot and humid in the summer - sometimes in the 90s. I enjoy time outside but don’t believe I’ve ever gotten a high temp alert for that - perhaps I’ve avoided being in excessive heat for too long. I have gotten a couple from sleeping on a heating pad and not realizing I had placed my pump right on top😳 - thankfully the warning went away after I moved the pump. I do wonder what people do when they wear their pump at the beach.

Forgot to mention that I live in Spain and we have that temperature ( 98.6F / 37C) and above in the shadows during june to end of september and I never have got a temperature alarm with my current X2. So if you have in in the pocket its safe :wink:

Great to know. Thank you both! And good luck upgrading your pump.

Like I said earlier, my 670g and Guardian 3 work so well together I can’t see why I’d switch to another manufacturer. I’ve been using a Medtronic pump since 1997 and their sensors since 2010 and they’ve always worked. Can’t wait until I upgrade to the 780. Very happy with my latest A1c of 6.5.


Hi Martin,

I saw your post from April 2021. I live in Canada where they at the moment only have the 770G. 780G expected to be approved this year. I am happy with the pump, but when the pump is joined with the CGM, they are not a good couple to me. I am considering whether to switch to dexcom/T-slim or wait for the 780.

I wanted to know if you are now on the 780G, and if so what your likes/dislikes about it are. The 770G only has a 6.7 target mode, which is too high for my liking. With the 780 what warnings are you able to adjust, or perhaps I should ask, what settings cannot be altered or customized?

Anything else that you may think of to bring to my attention that I have not asked about would also be appreciated.


In 2020, I had the choice between the TSlim/Dexcom/Control IQ, the 780G, and my endo presented to me the full pros and cons of both systems. I chose the 780G and upgraded it in January 2021. In terms of the pumps, there were two things I disliked about the TSlim - the reservoir (clunky, complicated, and unreliable) and the rechargeable battery that is also unreliable and should be recharged every day. In terms of the algorithms, the 780g is more flexible (three SG targets) and the auto-bolus more assertive. SmartGuard auto-bolus kicks in at or approaching 6.7 (120), every five minutes with sufficient bolus to take you back to target. Control IQ has only one SG target and the auto-bolus only kicks in at and approaching 10.0 (180) with 60% of a normal correction and only once/hour. In addition, the 780G “treats to target” whereas Control IQ “treats to range”. The Medtronic GL3 sensor is as accurate as the Dexcom but does still require 2x/day calibrations. Since June 2021, I received the Medtronic G4 sensor that requires zero calibrations for a 7-day sensor life. For me, the only advantage of TSlim/Control IQ/Dexcom is a fancier touch screen, thinner profile, and three more days of sensor life.

The difference with Control IQ is that any “basal” adjustments are “tethered” to the basal rate schema input by the endo/patient. The 780g automatically calculates the basa rate and the ISF every five minutes. The only driving force is the SG target of 5.5, 6.1, or 6.7, the SG level, the SG trend, and future SGs (30 minutes) as calculated by the algorithm. The internally generated ISF is also used when taking a bolus for a meal. With the 780G the AIT can be adjusted to increase or decrease the assertiveness of the auto-basal and auto-bolus. With Control IQ the AIT is set at 5 hours and this cannot be changed within Control IQ. As my AIT is currently set to two hours, partially due to Fiasp, Control IQ just isn’t flexible enough to keep me in range.

Hi @DT1Lada and welcome to the forum. I switched from Minimed to Tandem before the automated systems were in place so what I do know about Minimed’s system is primarily from what I read here in the forum. You provided some much greater detail about the functioning of the system that I was unfamiliar with so thank you for that. If I might say, from my 10+ years with Tandem I have not found the cartridges to be unreliable or even clunky - actually I wound describe then as streamlined but maybe that’s a matter of of preference. I wouldn’t call them complicated either, although sometimes I have to poke around for the insulin to go in - no problems with it “going out” though. That said, people do seem to prefer the less wasteful filling of Minimed’s reservoirs.
As for battery life, I’m fanatical about keeping my devices charged so I do typically plug when I’m doing something sedentary such as watching TV or driving. Even if I get down to 20% I’m back to full in less than an hour, and I get at least two days on a charge even when CIQ is particularly active. That said, battery use “in the wild” may vary by user and usage - there are some days when I look at my screen more frequently than others.
I’m glad to hear your endo was well versed on the pros and cons of both systems - I was already on Tandem when I started with my current endo a few years ago, and most of her pump patients were on Minimed at the time. It’s very helpful for the doctor to be familiar with them, particularly for patients who are new to pumping. Their willingness to share the pros and cons of each without pushing either can help prospective pumpers formulate their own questions for pump reps.
I’m had to hear you’re happy with your system. All the best and I look forward to your contributions.

Welcome, Andrew.

I’ll second Dorie. I switched from the Medtronic 670g to the Tandem X2 and it’s been much better for me. Obviously, you have your own style, needs, and priorities. But I feel like a few things here should be explored/corrected a bit:

I do agree with you that I prefer the Medtronic reservoir system to Tandem’s cartridges. But I got used to the Tandem system pretty quickly. I’ve never found the cartridges to be in any way unreliable. It is a little more complicated, and involves a little more waste (packaging and such that need to be thrown out). But it’s not all that different, when you get down to it.

The battery lasts for me. Once or twice a week, at my convenience (usually when I see it’s gotten down to about 50%), I charge it for half an hour or so, and that’s it. With the 670g, I had to buy rechargeable AAs, keep a few charged ones with me at all times, pop out the old battery once a week to swap it for a new one, hope I didn’t fumble the battery cap, hope the pump accepted the charged battery… Even before the battery cap broke and had to be glued back together (and the pump doesn’t work without it), that was a lot more fuss than the T:Slim’s internal battery. And if you’re using disposable AAs, then you’re generating a lot more waste, and battery acid is terrible for the environment. And you still have many of the same problems.

The T:Slim has different SG targets. Exercise mode raises it. Sleep mode lowers it a bit. And you can always program a personal profile with your own SG target, carb ratio, and correction factor. You can switch between programmed profiles at any time. That’s actually what I do because I need a more aggressive correction factor when I sleep but my sleep/wake schedule changes from day to day. So when I go to bed I activate sleep mode but I also manually switch to the sleep profile.

The 670G and 770G don’t do auto bolus. They adjust basal and they alert you if your SG goes above the threshold. But there’s no auto bolus function. I don’t know if they added that for the 780G. Tandem literature did not do a good job of explaining their system by my estimation. The X2 adjusts basal every 5 minutes similarly to the 670G, but it also gives an auto bolus up to once per hour. The correction bolus isn’t the full correction bolus it would attach to a manual bolus, but you’ve still got the basal adjustment to back it up. And you can give a manual bolus at any time. (I find that if the correction bolus isn’t enough to bring my BG back down, I can just give myself an extra couple of units, depending on the particular circumstances, and if it turns out to be a bit too much, the pump will reduce basal enough to make up for it. Not how you’re supposed to do it, but it works for me.)

As for sensors, I found the Guardian 3 were very unreliable for me. They regularly took a full day to calibrate properly, often cut out a day or two early, and were prone to false alarms. The Dexcom, on the other hand, is so accurate I’m fairly confident I could get away without calibrating at all. I still do test daily to be sure, but I’ve almost never had a BG reading that was significantly different from the SG reading. I insert the sensor, within 2 hours it’s working smoothly, and it almost always lasts the full 10 days without trouble.

It is nice that Medtronic followed Tandem’s lead in making the 770G and later pumps wirelessly updateable. 670G and 770G are almost identical except for that functionality, but to make any software change to the 670G, I’d have needed a whole new pump. Not sure how the Medtronic phone app is, but I’ve really liked the Tandem one. It keeps up with the pump in realtime, relays alerts, and automatically transmits data to the cloud so my doctor can see. It also gives me a graph that combines SG values, basal values, and bolus values in one easy chart that I can scroll with a touch.

Otherwise, the pumps are fairly similar and individual needs and experiences will vary.