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.