Trouble with DexcomG6

Does anyone else have trouble the first two days using the Dexcom G6 sensor after changing it? When I change the sensor which for me never goes beyond 7 days I have 2 days of the worse inaccurate looking blood sugars. I practically go through a bottle of 50 test strips during those two days because the CGM says I’m going low, or am low <70 when actually I’m around 130! Then it waffles back and forth. This happens after I’ve calibrated it too. I’ve learned not to trust the CGM those two days because in the past I would take O.J. and then of course not really being < 70 and actually over 120 then I go high!

It’s so frustrating. A diabetic consultant told me I might have an overactive immune system and should use Benedryl cream or Flonase on my skin 15 minutes prior to inserting the new sensor, then wash it off as this will suppress my immune system while my body gets used to a new sensor. Has anyone else ever done this or had this type of issue? I’ve also tried ‘soakng’ the sensor for 6-12 hours but that doesn’t seem to help.


Not sure that I can help per se but i do have the same issues. I will have to calibrate at least once and the last 3 months or so (new shipment) it’s more like 3-4 calibrations needed. I’m lucky that I have other clues that can help me decipher if I need to calibrate or not(I can tell BS within about 20pts by how I decipher the taste of water. For me the tastes change depending on my BS level.). However, I’m a MDI so the main times I’m most concerned about accuracy is when I’m dosing my short term insulin, and it’s not a steady thing (from what I understand on pumps. I’m totally ignorant on them at this point) that needs more consistent numbers.

I’m not sure what to tell you except maybe just take it as a given that the first two days aren’t going to do well until the calibration kicks in. And just take it cautiously those 2 days. Sorry I can’t offer that much help.

I am on my first sensor. My numbers were all high or low for 2 days. I woke up it said 60 but I was 85.
160 was really 141.
Only after 2 days it suddenly was perfect. I’m going to try to restart this one when it is done only to get stable numbers not because I’m saving sensors.
I restarted my entire sensors and ended up with a bunch of expired ones so I did the really save anything.
I will try soaking for a day on my next sensor.

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Just so you’re aware, restarted sensors will read really high at first. You can go ahead and calibrate it right away, but it doesn’t like discrepancies more than 60%. If it’s more than 60% off, split the difference into two different calibrations.

I always try to be between 80 and 100 when a restarted sensor ends it’s warmup. It makes the first “off” numbers more manageable for calibrations and not upsetting pump automation.


What locations have you inserted it?

I get better results back of arm or inner thigh. I use stomach for pump.

Sometimes thinner area don’t work as well for some people. Could be a bad batch. Have you called dexcom support ? They can review in more detail, and may send new sensors.

Hi Jenn,

Thanks for your response. Yes, I have to calibrate everyday cause the Dexcom tells me to calibrate. These bodies, right! Somedays I just want to scream.


You are prompted to enter calibration ??

Did you enter the 4 digit code when you started it ?

That helps. I’ve been waiting for the morning fast usually to calibrate. I do this when it’s more than 15 points off.

I always start my sensors with the 4 digit code. Some sensors read consistently high or low. In that case I calibrate. This does not cause the dexcom app to prompt me for re-calibrations every 12 hours. I don’t get any requests for re-calibrations.

I have been using the backs of my arms since my first cgm more than 10 years ago. It’s the only place that stays consistent. On my belly they tend to fall out. On my sides they get sheared off.

MM1, I put the sensors in my abdomen. I pinch an inch of skin and insert it in that area. My pump is also on my abdomen at least 2” away from the sensor and my belly button.

Yes the sensor tells me to calibrate every day. Yes always enter the 4 digit # on my phone.

That’s odd and not how it usually works. The 4 digit code is normally prompted once at startup, and if not entered asks for BGs. You could call tech support to see if they can diagnose why it isn’t doing that.

Yes, I do for most sensors. Also I never restart a sensor because by the 10th day they always start to show noise.

My last sensor also prompted me to re-calibrate multiple times despite entering in the 4 digit code on startup. I believe this was due to its inability to make sense of my initial calibration - my meter reading was significantly different than the sensor reading. I’ve read one trick to prevent this (but have yet to try it), is to enter a calibration number that is midpoint between the meter reading and the sensor reading. Next time I will try that!

But, yes, unfortunately, I, too, experience inaccurate readings for the first two days, then the next 8 (if it lasts that long), are very near to my meter readings. I’m not sure how to resolve that! I’m on Loop so those first two days cause havoc with my BGs. I really should open Loop on those days. That will be my next strategy!

Do you mean you shouldn’t open Loop on those two days? Please let me know if that works.

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No, I mean I should open Loop on those days so that Loop does not control the bolus and basal based on the inaccurate Dexcom readings as it does when in closed Loop!! If I open Loop I can at least control the bolus and basal based on my meter readings.

It is not always obvious I’m getting bad readings though so in the meantime Loop reacts to the BG readings for better or worse!

Oh, ok thanks. I am not on Control IQ yet so I misunderstood what you were saying.

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Mine are usually off for the first 12-24 hrs, infrequently for two days. Past 2-3 days in regards to calibrations, I’ve noticed a tendency for sensors to return to high or readings within a few hours of a calibration and all the sensors in a box having a similar biases. When inserting sensors, I try to have the the inserter resting lightly on the site and also keep the sensor at least 4-5" from infusion site.

When I first started on Dexcom G5 I was horrified when my sensor and finger stick were not in line. Called Dexcom’s and they said this was normal I think he said 20% difference. Obviously not a diabetic. But it did settle down after a day or so. Switched to G6. Same thing. First day not really accurate. I wear on upper arm.

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I think the folks who started on the early medtronic and dexcom sensors have a different perspective. There has been tremendous improvements in CGMS
and bg meter accuracy. Have come a long way from measuring glucose in urine in a test tube.

(Same for computers, cell. Phones,cars, etc)