Medtronic 670 G Review - Neutral
First off, this is not medical advice. Only my opinion and how I use the pump. Consult your doctor on any medical decisions.
The 670G is a hybrid closed loop system from Medtronic. I switched over to this pump after years of using Dexcom, along with the Medtronic 710 insulin pump. I was excited about the algorithm to adjust my basal rates. The pump has a few modes: auto-mode and manual mode. In manual mode, the sensor data displays on the pump and suspends when your blood sugar reaches the low threshold. In auto-mode, using the Smart Guard technology (the Guardian sensor) it auto adjusts your basals using a target range of 120.
There are limitations to using auto-mode. Firstly, you cannot adjust the basal yourself. If you are running higher than you would like with the correct information (carbs eaten, correct settings for carb ratios and ISF, etc.) you have to trick the system to give you more insulin with “fake carbs”. Most of the time this is because of the system not being able to factor in the impact of fat and protein in the food I ate, or sometimes because of the adrenaline high after playing hockey.
Pro’s to the 670G
I like that I don’t have to carry my phone around all the time.
I like how I don’t go low at night anymore. When outside variables (food and exercise being the main ones) it tends to do pretty good with keeping me in range.
I snack less because I tend to not run as low. I probably had my basals running higher than they needed to be pre-670G.
It is the first of its kind and I believe the future of diabetes management, where the sensor communicates with the pump and self adjusts.
It takes up less of my mental energy and effort by adjusting my basals (when it is working correctly).
The insertion device is generally pretty painless.
The tape is better than the Dexcom system and will stay on for the duration of the sensor, whereas with the Dexcom I sometimes would have to buy additional tape systems to keep it on.
There have been two versions of the transmitter. Make sure you have (at the time of this writing) the second version of the transmitter. It works much better than the first and will kick you out of auto mode way less than the first version did.
Cons to the 670G
You have no control over the target range. It is set at 120, and there is absolutely no way to change this. This may be higher or lower than you would like.
Overall the pump is very conservative. Per FDA regulations, ISF and Insulin Duration, it will take a while to bring you back into range from a high blood sugar. Per Saira’s experience with Loop as well, this is partly because of insulin resistance that kicks in once we are over 250 anyway, and also partly because of how fast it takes for Humalog to reach its peak performance. None of us have tried Fiasp so I can’t say if that would make any difference or not. Not sure if this is an issue with the algorithm or Humalog.
The pump needs calibrated at least every 12 hours per Medtronic, but realistically I find myself calibrating about 3 to 4 times a day. I envy Dexcom G6 users that do not have to prick their fingers at all.
The Guardian sensor is not very accurate for me. It usually says I am lower than I really am. More often than not, it says I am 20-30 points lower than a finger prick confirms, meaning if auto-mode is trying to keep me at 120, I more realistically running at a target range of 150 based on the accuracy of the sensor.
The Guardian is even less accurate on the first day of insertion. It can be off by 100 points. This can be frustrating if you are making decisions based off the lower number. Also on the first day, you need to calibrate more often.
The Guardian is also pretty off on it’s last day with the same levels of inaccuracy on the first day.
If the Guardian is pretty inaccurate, it will not accept the calibration. For example, if the sensor reads at 100 but you are really 200 per a finger poke and you try to calibrate it won’t accept it or adjust the sensor reading accordingly. I have found in these situations, especially on the first day, you have to gradually bring the blood sugar up to the real amount. There is a formula that the medtronic representative told me and it pretty much works to eventually get the sensor to read accurately. You have to calculate the “Cal Factor” by taking the accurate blood sugar divided by the ISIG number (found under sensor status in the pump menus). If the Cal Factor is between 2 and 8 it should work. (I am told the new transmitter allows for the Cal Factor to be between 2 and 16 - but I have not always had success with this and personally stick to the 2 to 8 rule) If it is outside that range you should wait to calibrate. Or I enter in a fake calibration that fits within that window.
I don’t like that you have to wait to charge the sensor again after each use. This takes a few hours and when you are used to wearing a sensor this time is annoying in between charges.
Dexcom vs. Guardian notes
The Guardian has even more of a lag than the Dexcom system. We have all been told that the sensor is usually 15 minutes behind real time finger poke readings, but in my experience the Dexcom is quicker to react to real time blood sugars than the Guardian.
I never change or put in a new sensor at night. This is because of the inaccuracy and also it makes you test much more after putting in a new sensor and I just don’t want to wake up at night to calibrate that often. This means I have to go overnight without auto-mode in between sensor changes.
I feel the technology of the sensor is behind Dexcom for three main reasons. 1) Dexcom is more accurate. When first getting the Guardian Sensor, I wore both the Dexcom and Guardian and found the Dexcom to be more accurate and more responsive to the blood sugar changes. 2) The Dexcom G6 can be worn for 10 days, whereas the Guardian can only be worn for 7 days. 3) You do not have the calibrate the G6, whereas you still have to calibrate multiple times per day.
I have not been able to use the CareLink system yet. It didn’t work on my Macbook air and I have been lazy in trying to figure it out. I really liked how with Dexcom I could just use the Clarity app to give me reports on my daily averages, standard deviations etc. You can do this through CareLink with the Medtronic, but it is much more cumbersome than just clicking an app.
There is no follow app for Saira to be able to know if I am falling low. This was a really useful tool for us with the Dexcom because I travel a lot for work. But the 670G keeps me running higher anyway so we haven’t really had to worry about lows unless I’m not in auto-mode.
Conclusion
All in all, I have decided to stick with the 670G because of all the pro’s I listed above, and the con’s not being enough to make it worth paying out of pocket for a new system since insurance won’t cover an upgrade again for another 2 years or so. My biggest gripe with the 670G is 1) the inaccuracy of the Guardian sensor 2) the inability to set your target range lower than 120 3) the inability to set a temporary higher basal based on higher fat and protein meals or the impact of adrenaline in sports. There is no version of an extended bolus while running auto-mode.