G6 readings recently 60 - 100 points off from finger stick

I have been using the G6 for a few weeks. The first two sensors failed or got stuck in the first couple of days. The next sensor worked almost perfectly for the 10 days. The next one was fair but not as good until the ninth day. The readings wre off and when I tried to calibrate, I was told to do another calibration at a certain time - about 10 -15 minutes later. Entered the new calebration and another similar message came up with a time in the past! Since it was almost the 10th day, I put in a new sensor last night. The readings from the monitor are not even close to finger stick readings and unable to calibrate corrections – in some instances almost 100 points off.

When the one sensor worked great for 10 days I thought this was wonderful. The only finger sticks were in the morning and nght to verify all was well. Based on more recent experience, I am considering going back to the G5 with all of the issues on that model.

Tried call Dexcom support but had to leave a message for a clalback which has not occured several hours later.

Very frustrating.

Good luck. My first sensor with the G6 a couple of weeks ago gave me readings more than 200 points lower than they actually were. It started off at what I expected to be about right, but dropped and dropped in the first few hours and started sounding the alarm of serious low. I knew my BG was having a serious high at the time, as confirmed by glucometer and the Freestyle Libre that I still had a couple of hours of time left on the sensor. Had to hide the Dexcom on another floor to keep from hearing the alarm all night, since one can’t shut it off. The next day I tried to calibrate the thing, but got calibration messages similar to ones you did. Then it gave message that the BG numbers I gave were not within expected range and it refused to accept them. Then I landed in the hospital for other reasons and had several days without a record. When I got home from the hospital I found no voice mail that Dexcom had tried to return my call.

I did, however, get better results when I used their chat line after I was out of the hospital. They replaced my first sensor and the second sensor seems to be working fine. From my limited experience, I’d definitely recommend chat over call-back.

Sounds awful. I get readings like that with all of them but I am not looking forward to changing to G6. Because you only get 3 sensors a month and I probably won’t have any back ups to start with. if they all fail like people say they do, it could be awful. I will be continuing to calibrate anyway.

I will have to leave them in longer if that’s possible which is what I used to do with the other ones which is why I have a back up in case some fail. Stop doing that because I was getting terrible irritations from leaving them in so long or even sometimes when they were in the regular amount of time.

It will be even worse when they have it so there is no transmitter and all you have is a sensor and that fails- what are we going do then?

You will have to call today. Be prepared to wait on hold 1 hour. Keep in mind that is possible the whole shipment is sketchy. keep a close eye on it. I’m calling today too. I get a new shipment today. Fingers crossed its ok.

I’m gonna sit on hold while I take my dog for a long walk.

Yikes. Mine has been just about 100 percent trustworthy. Sometimes a tich high but usually just right on. I would go back to the Libre if it wasn’t working this well. Hope you figure it out!?!

I can’t believe that for once i am in the “it works for me” category. I am not in the ‘easy to learn’ group either but I went from G5 to G6 in January and after a bit of a rough start, I finally, after several tries, learned how to restart the G6 to get 20 days. I do not push beyond that. That has given me a couple of backups.

Also, I have calibrated a few times but have rarely gotten a recalibrate message and then only once for no specified time. After I very occasionally recalibrate it works well enough for me after one or at most two calibrations. If I am within 50 points I let the dex work itself out and it usually does.

I do not have an explanation for those with the weird recalibrate messages. I am a believer in using my arms for the vertical Dex site but I am not skinny so that may not work for those who don’t have much subq tissue on their upper arms.

I am having no luck getting callbacks or getting through to tech help but have gotten my supplies so far. I have muddled through when I thought I needed help.
I would encourage you to call first thing early in am and keep at it. I have been on hold for way longer than one hour, with no luck, therefore, you may need to keep your phone plugged in!
In your case, I would just stay on the phone if possible. I turn on speaker and work on my laptop. Good luck.

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My DD just started on the G6 yesterday after many years on the G4 and g5. We also just updated to basal IQ yesterday (we’re Canadian). 6 hours after insertion, it was off about 5mmol so we calibrated. Since calibration the numbers started jumping all over. Basal was suspended twice, then it quit reading - no numbers available. She woke up on her own at 2.6mmol without any alarms. Boo. The G6 taking a break when you need it most irks me. My question is, should I not have calibrated? If you can’t rely on the accuracy of the G6 for 24-48 hours, how is that acceptable? Sleepless and not happy!

I sometimes get bad results with my G6 during the first 12 hours—just as I did with G4 and G5. At least sometimes with G6, it starts working accurately right away. My experience is that calibrating in this initial period rarely goes well. I started a new sensor on Sunday and it was inaccurate and erratic. So I calibrated and it went crazy from reading too low to reading too high, I calibrated one more time and it didn’t settle down.

So I did what I used to do with Medtronic SofSensors in the dark ages of CGMS. I restarted the sensor and it has been working great ever since.

It is a PITA to restart a G6 sensor compared to G5. I do the procedure where I stop the sensor, remove the transmitter for 30 minutes, and then start the sensor again with a code. I use the restart procedure from this video.

Thanks for this tip!

Just curious, does everyone know that the G6 is marketed as not requiring calibrations? For example, " The Dexcom G6® CGM System is designed to work properly without requiring calibrations." found at https://www.dexcom.com/faq/how-do-i-calibrate-dexcom-g6®-first-time

That marketing claim, however, seems to be contradicted by more and more G6 users reporting once- or twice-daily required calibrations. In my searches, I’ve found mentions of required calibrations for Dexcom G6 on reddit, JDRF forums, and here.

Is this a software bug or is Dexcom making false claims in their marketing?

We know, Mitch. You wanna take that with a grain of salt. I wouldn’t classify it as a bug or false marketing (although one could make that claim). Its fundamentally so that they can work with medicare pts.

My doc made me accompany any sensor data with manual stick for, like 15 years, when I was on G4. It always worked like a charm, so I’d be like, “Yeah, yeah, Dr X. Whatever.” But, now I recognize the value in what she was saying.

OK, Bluebird. I’m gonna call right now (early) on your advice. Anothere sensor failure last night (it got stuck). Total call time was 16 min to report 3 failures. They answered right away. I got lucky!

Dexcom’s TV ads and the web site have the following [in small print]: "If your glucose alerts and readings from the G6 do not match symptoms or expectations, use a blood glucose meter to make diabetes treatment decisions.

Started on G6 two months ago. Went smoothly for awhile. Worse thing was when it says you are low (even if untrue) it takes forever to reset. Beep beep. Lately has been totally erratic and have been doing finger sticks x 4 times a day. Have been wearing on upper thighs. No problems until lately. G5 always worked. Going to switch to back of arm today. Am on Medicare so I can always talk to someone. For what it’s worth. Had problems with Medtronic’s and Dexcom this week. Had a much easier time with Medtronic’s. They communicate and will put you on hold while they call your Endo an straighten out problem. Then ship overnight. Send you new infusion sets to try and actually suggest sets that may work better for you. Then ship overnight. Not Dexcom. Guess they don’t make enough money to ship overnight. Seriously may try the freestyle Libre. Have never tried to calibrate so can’t speak to that. Well gotta go. G6 not receiving readings no big surprise there.

I am on the verge of getting the Dexcom G6. My first CGM EVER. Now reading this I am not so sure. Should I wait until they work out the bugs? Do they replace faulty sensors or are you just out of luck?

Yes, they replace sensors, and transmitters/receivers if under warranty.

Most work fine, and waiting won’t really make a difference for you. The next version, G7 will likely be delayed because of COVID and delay of doing trials for FDA approval.

I have had maybe 1 out of 15 sensors with errors, and one transmitter error, all replaced.


New sensor can be way off the first 12-24 hours then work great. I just plan on extra fingersticks the first day. A trick I use is to enter the calibration twice. First entry brings the sensor to about halfway between. The second brings the reading to exactly.

I recently had a sensor that was off 50 the first day and could have requested a replacement. Then the next day it was reading close and was fine for the other 9 days. It’s a real conumdrum how soon to give up on a sensor. On one hand a sensor may or may not be on track with a little more baby sitting. One the other hand, the replacement sensor may way off at the start.

Do you mean you enter to calibrations 15 minutes apart or two calibrations one right after the other?

No. I mean I enter the same number twice at the same time.