I have used an insulin pump to manage my diabetes for over fifteen years. I am currently using an ACCU-Chek Spirit Combo pump with Humalog, an ACCU-Chek Aviva Combo meter, and a Dexcom G4 Continuous Glucose Monitor (CGM). The ACCU-Chek Spirit pump has been discontinued, so I am considering a new pump and CGM system. I am considering the Medtronic MiniMed 670G system with SmartGuard - Guardian Sensor 3 CGM.
I am interested in hearing from MiniMed 670G pump users regarding your experience with the 670G pump and the CGM.
I have heard that the Continuous Glucose Monitor (CGM) sensor doesn’t stay in place and may require additional medical tape to keep the sensor in place. Do you need to add additional tape to hold the CGM sensor in place? If so, how often and under what circumstances do you need to add tape?
I understand the CGM needs to be calibrated, I believe initially with two finger stick blood tests and then twice a day. I have heard that the CGM may request additional finger stick based blood test results more frequently than twice a day. How frequently does the CGM request additional calibration blood tests beyond the usual two per day?
I’ve been using the 670G pump since early December of 2017.
I like the “Auto Mode” but have been going through glucose test strips twice as much as before the 670G.
It asks for calibrations continuously even after just taking a blood glucose calibration.
Yesterday I went through 6 test strips in under 15 minutes!
It’s costing me lots of money to purchase more test strips because my insurance only covers so many per month.
Is anyone else having these issues?
I myself am very familiar with this pump and sensor because I have one. I actually am a Medtronic Minimed Ambassador so if you would like I can direct you to the right people and try to see if they can get this issue solved for you.
It seems like @momoftwins and @BKDesign haven’t had an opportunity to respond to your questions but as a user of the MM 670G for currently 22 weeks and counting in Auto Mode I’d love to share my experience and help to answer your questions. Hopefully my feedback is still helpful to you @jaegerbt or anyone else who stumbles upon this thread.
On to the questions!:
Well, if you mean that you’ve heard that the CGM won’t stay in place very well with only the adhesive under the sensor and transmitter, you would be correct. Medtronic’s user guide for the 670G/Guardian Sensor 3 is the first to admit that additional tape is usually needed (and expected) to keep the sensor on for the full seven days. Your boxes of Guardian Sensor 3’s come with the necessary tape and in my personal experience it is more than sufficient to keep the sensor in place. Here’s an image from the user guide that may shed some light on the issue.
So as you can hopefully see, you’ll be using two of Medtronic’s provided oval tapes for each sensor. It’s not a bad setup by any means. Sometimes I will forgo the second tape over the transmitter to save on adhesive irritation and will apply a Tegaderm film over the whole thing when necessary. I’m doing that for the sensor I’m wearing as I write this and with one tape under the transmitter the entire thing holds but the adhesive under the transmitter is prone to come loose and make the entire thing prone to being caught on clothing, but that’s about it. I have sensitive skin so you shouldn’t have issues with just wearing the two tapes unless you’re like me in terms of sensitive skin and adhesive.
Much like your current Dexcom, the Guardian Sensor 3 (for the most part) needs a calibration every twelve hours. As you seem to be aware of, Medtronic’s sensor has a different calibration schedule for the first 24 hours of the sensor. From the main 670G user guide on page 216 (which can be found here, the first link) you will first calibrate your sensor after anywhere from 45 minutes to 2 hours after connecting the transmitter to your newly inserted sensor. Your second calibration will come six hours after that first calibration. You will do your third calibration within 12 hours and this 12 hours between calibrations will remain true for the life of the sensor.
Except for the fact that you shouldn’t calibrate only when asked/the bare minimum. Medtronic recommends calibrating three to four times a day spread out over the entire day to improve accuracy on page 219 of that handy user guide (which I’ve found to be true). A fingerprick before meals when your BG is likely stable is a good time (for me at least) to calibrate (and ensures you are dosing any corrections off an accurate number at mealtime).
And as you mentioned, the CGM reserves the right to ask you for an additional calibration at anytime. You might expect this to be annoying, except it almost never happens (and there’s probably a good reason if it does). I say this because to my knowledge Medtronic’s latest sensor/transmitter duo is equipped to self-monitor itself for any abnormalities/inaccuracies that may affect the safe use of Auto mode. Most anytime it asks for an additional cal is because it is too far off from a recent fingerstick that the system raises red flags. Situations like this aren’t usually difficult to fix (just calibrate after a little while (immediately to an hour depending on BG trends and any sensor issues). I’ve also had the occasional sensor that doesn’t read very accurately and the CGM in such a situation, thanks to its self-checks, will employ a combination of “Sensor Updating” events (where you stop receiving SG values for a time while it tries to fix itself) and additional cals to try to bring the SG values back in line with your actual. For minor sensor issues this works well and can help prolong the use of sensors that aren’t working optimally but oftentimes when a sensor gets to this point it’s best to trade it out for a new one. This would be a good place for others to chime in.
In my recent experience, a properly working sensor that is being calibrated will not ask you for additional cals until that is no longer the case. My first three months of Auto Mode I didn’t have a single sensor fail prematurely and had the once-in-a-while accuracy issues. I’ve only had to send one sensor back to Medtronic for a replacement that failed on it’s third/fourth day after going in and out of sensor updating three times in a day to try to fix itself.
As accurate as your carb counting, sensor values, and bolus wizard settings are (carb ratios, correction sensitivity, active insulin time, etc.) With all of these dialed in well (and enough time for Auto Mode to learn your BG trends) Auto Mode is pretty darn perfect in my opinion while also erring on the side of safety. I can say that it sure as heck beats set-in-stone basal rates and relentless temp basals to keep up with life. I think the best way to sum it up is that it makes good decisions but might not always work as quickly as you might like. I find it’s much better at stopping basal delivery after over-dosing a bolus than giving extra after an under-bolus, but it’s nothing I would complain too much about. It really shines overnight when there isn’t a boatload of carbs to fight against and it will fine-tune the crap out of the times when food and IOB aren’t interfering with it’s work. See the below picture from the last 5-6ish days of my management (pretty sure it’s some of my best management ever, by the way) and compare nighttime to daytime)
(I also want to note that 10:30pm-3am sees me go higher after having 4-16 carbs and some protein with half the recommended bolus at best and no insulin at worst to quell my parent’s somewhat irrational fears of nighttime hypoglycemia from a freak pump malfunction/life malfunction (I’m 17 for context, so still living w/ parents) even though Auto Mode just kicks in and corrects any raised BG safety buffer back down to my perfect 120 after a couple hours anyways.)
Point being, I struggle with a bit of post meal hyperglycemia (it’s usually a bit worse) during the day but at night (save for spike-inducing snacks) it runs as flat as a pancake. I wouldn’t hesitate to say that nighttime can show the 670G in its best light possible, but for me personally I have seen massive improvements over the entire day.
To sum up this really long post, I think the 670G is the best thing you’re going to be able to get for the next year or three until other pump markers catch up. Is it perfect? Hell no. Is it better than anything else? I think so. I think Dexcom gives the Guardian Sensor 3 stiff competition but I’ve heard horror stories from both CGM camps (especially/mostly for older models though) and I can say that at least on paper they aren’t far off from each other. Unless you’re already running your BG on a hyper-fine gradient I think you could benefit from the 670G and even then it reduces the factors at play when fine-tuning other factors like carb ratios because your basal rates are almost always optimal for the situation and my personal slogan for the pump, it gives you more results for the same amount of work.
Thanks for reading, and please reply or @mention me if you have any questions. That goes for anyone interested in the system as well.
*not affiliated with Medtronic or licensed to provide medical advice if it isn’t obvious/implied.
Yes! Everything @Chancey said is accurate! I can add one more tidbit if you promise not to tell anyone…I have comfortably used the same Sensor site for 2 weeks before changing. I could probably go longer but don’t want to risk infection. For the second piece of tape, I cut it in half and place it under the strip of tape holding in the transmitter so I can remove the transmitter easily after one week for a recharge and “reconnect”. The tape seems to be very sturdy. I workout almost every day, shower and sometimes swim. As I approach the end of the second week, the edges of the tape are starting to come up. This being said…if I get a “Sensor Updating” message, I know it is definitely time to change the sensor. I hope this helps in your decision making process.
Let me also address the other 2 questions for you.
2. Calibration. I have been using the 670G for many months now and I usually only have to calibrate 2-3 times in a 24 hour period. When you are a new user, the AutoMode is still trying to figure “you” out so it most likely will ask for more finger sticks. If you look at it this way, it does not seem unreasonable: the pump wants to make sure it is doing the right thing! I respect that.
3. AutoMode accuracy. I think it is very good! If I miscalculate my carb intake, however, automode is not designed to compensate for this, so it will ask for a finger stick if it has had to deliver outside of it’s “range” for a period of time. Only thing I dont’ like is that the range for automode is hard coded at 120. I like my average to be lower than that. Yet, automode has made my life so much easier, that I am willing to accept this higher number for now.
Yes, it will need to be fully charged or it acts up. But if I have an awesome site I hate to loose it. So I disconnect, charge and reconnect as a new sensor. Of course I still have to go thru the 2 hour warmup period…
Yes, of course! My goal is to change sites as little as (safely) possible. I’d been thinking I’d like to try to get another week out of my sensor, but I wasn’t sure how. Thanks for the info, I will definitely give it a try.
I have been using the 670G for about two months. The main issue I have had is the first day I change the sensor each week. The sensor glucose (SG) readings can be VERY inaccurate the first day. I’ve contacted Medtronic tech support and their answer is “this isn’t uncommon”. It takes a while for the SG to get in line with your actual blood glucose (BG). There are a few tips/tricks I’ve used that may (but not always) help the first day issues. This is not medical advice – just my experience.
Go out of auto mode the first day. Until SG and BG closely match, auto mode gets very confused and can go into a loop.
Insert the new week’s sensor and wait a couple of hours before attaching the transmitter. You kinda have to do this anyway because the transmitter battery needs to be recharged. It gives the new sensor time to set-in and get better readings before actually starting the warm-up period.
I’m not ready to throw the 670G in the garbage due to these first day issues. But I can says I have a love-hate relationship with my new 670G system.
ALWAYS check the ISIG (under status > sensor) before calibrating. Never enter a BG value higher than 8x the ISIG. For example if ISIG is 20, don’t enter any BG higher than 160. Instead delay the calibration.
Hope this helps. Questions and comments are welcomed.
I’ve been a Medtronic pump user for over 12 years. I changed over to the 670G in January. Auto mode is great when it works. It’s important to remember that it take time for the System to learn your patterns to operate optimally. I still have times when looping occurs but agree with other users that this is a software issue not a sensor issue. I have tested this by leaving the sensor on and turning auto mode off for a period of time and everything worked fine. I have also been told by the Medtronic support staff not to calibrate more than twice in an hour - even if the system is asking for BG. Ignore it and come back later.
Taping- I have very sensitive skin and the double taping method recommended irritated my skin tremendously to the point of getting skin welts. I have recently tried Grifgrips and they are amazing! Grifgrips secures the CGM to my skin for a full 6 days, stays in place through rigorous exercise (kickboxing) and removes easily without irritation. Highly recommend!