CGM wildly off from meter reading

Hey everybody. I was wondering if anyone has a suggestion before I call Medtronic tech. I have Medtronic 670 Guardian, I started new sensor yesterday. All seemed fine. I last calibrated early this mornining at 6:15 a.m, with a 150 BG. All seemed fine with BG seeming to go downhill to 70 with arrows down at lunch. I had taken no boluses. Curious, I did finger sticks. One meter said 278 another said 300, so I abandoned the Suspended Basal mode, because I was very high, not low.

Are there any suggestions on getting it back on track? If I calibrate with that large difference, it’ll certainly put me into Sensor processing or sensor failure. Any tips on how to save it? I sure would hate to have to start with another sensor and 2 hr wait time AGAIN. Lol

@HighHopes If a subsequent calibration doesn’t fix it, then it is highly possible the sensor is no good (bad sensor or bad site) and needs to be replaced.

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Well, that’s true. The longer I wait, the later I’ll be tending to it this evening. Oh well, I guess I’ll bite the bullet, call Medtronic and get it resolved. I’m pretty sure they’ll have me calibrate, but at least they’ll send me a replacement sensor. It’s just such a pain to go through TWO straight days of new sensors. :face_with_raised_eyebrow:


Calibration adjusts range offset, not linearity. Test the sensor/site. If a sensor/site is bad, it won’t respond just not respond with the right magnitude change, it may not even respond in the right direction to 3 glucose tabs or a 1 unit bolus. A BGM will. The same is true of a bad infusion site/cannula.

As it turns out, the calibration was not accepted. Then…Sensor processing started. It was getting late in evening so I called Medtronic…no one was available. I left my number for them to return the call. They still haven’t called me back.:frowning:

My suggestion to get back on track would be to depend less on CGM and more on finger sticks, which are more accurate and reliable. I’m sure that I’m in the minority here since I don’t use CGM and am not willing to trade accuracy for convenience, but good decision-making is undeniably tough when you’re basing it on bad data. I think CGM can often help but there are clear disadvantages.

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I frequently have issues with Medtronic’s CGM. They just changed their replacement sensors to be mailed with your next order, which could be 6 weeks out. I call them frequently. And, also twice in two days. It is a pain. If they are that far off, calibrating again may or may not fix it. I just do what the pump says, and usually I get to replace Sensor. It does stink when it messes up evening and night time with calibration requirement or sensor updating beeps every 30 minutes. I have started turning it off and turning it back on in the morning. Better to get my sleep and be a little high. Can’t wait for January and my pump warranty will be over!

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Getting reliable readings from the MiniMed 670G can be a real challenge if I do not calibrate properly and optimally. In my case, for my initial calibration, I have found that the best time to calibrate is in the mid to late morning about 4-6 hours after breakfast when my blood sugar is low (110 to 120) and going sideways. On the other hand, if your blood sugar is rising or falling at the time of a calibration, this can result in subsequent goofy readings that do not seem to correlate with your blood finger sticks…sad to say. As for a high calibration, I do this about 1 1/2 to 2 hours after a meal when my blood sugar is peaking. To have a sense when it is peaking, just check your blood sugar reading every 5 minutes and you (hopefully) eventually see it slowly rising (in my case, for example, a blood sugar of about 170 followed by a blood sugar of about 171,172, or 173).

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I actually don’t normally have an issue with the CGM being off from the meter. Not lately anyway. When it does happen, I hold off on calibrating when a BG number is being displayed. I wait until no number is displayed and it’s notifying me that calibration is required. And, then, I’ll ensure the meter BG number is at a reasonable level. I try to ensure it’s under 225. I also avoid calibrating if I’m under 80.

Unfortunately, the technology of the meter is kind of goofy if you are not careful. More specifically, if you wait until the meter is not displaying a blood sugar number and prompts you to calibrate, you are most likely going to calibrate when your blood sugar is rising or falling, not going sideways. The end result can be drastically incorrect pump blood sugar results that do not correlate at all with finger stick blood checks…

I switched from the 670 to the 770 a little over a year ago. For me when sensors started doing that they were on their way out due to either bad site or sensor. I would just calibrate until it failed and put the transmitter on the charger. If it was early enough in the day I would start a new sensor, if too late I would shut all the sound off so it would not keep me awake with alarms and start a new one in the morning… I would do a blood test before I went to bed and try to keep the sugar about 130 so I wouldn’t go low in the night.

Yet another reason not to use Medtronic, if they have no one available to help. Help needs to be 24/7 for these things.

I agree about Medtronic not having a tech available being an issue. This only started about a year ago. Before then, I always gotten a tech immediately. This was the second time that I left a callback number, being assured I won’t lose my place in line, that no one ever returned the call. It’s weird.

interesting. I have called several times in the last year and have always gotten a tech. My local rep would definitely be getting a call if that happens to me…

I don’t recall ever not getting in touch with a tech! About 3/4 of them are clueless if you have a problem that their script doesn’t cover your problem though.

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