Daily calibration of Dexcom G6

Well it may have been a bad sensor. My first one ever!! This afternoon I got the dreaded “No Readings” alert. I waited 3 hours, called Dexcom, and they said ditch the sensor and set up a new one. Still the info here was very helpful and thanks to everyone.

Its appropriate to calibrate in those cases. I think your only supposed to try calibrating 2 x per day ??? Am I correct? If that doesnt do it, declare the sensor faulty and pull it and replace it.

If you call them again, ask them to explain the 20/20 rule. Thats not in the manual, but its the most important protocol. Talk to the nurses, not tech support.

For best results, I found that the blood Glucose meter and the G6 comparison, must be done after a 2 hour period of not eating any Carbs.

Some things the give me trouble.

  1. The transmitter battery is supposed to last for three months. But usually after one month, the transmitter battery shows “Low battery”. After that the transmitter quits transmitting for a period of time, then starts working again. When the transmitter battery is low, the readings are very unreliable. One time a so called new transmitter read “Low Battery” right out of the box. Dexcom said that the transmitter has been in service, used by someone else, a few months before I started using the transmitter.
    (I’ve run out of time)

Cool, I think they first had 30/30 rule when G6 first came out. So they made improvements in sensors?

Or testing showed that it was in the 20/20 range for an acceptable percentage.

30/30 rule mentioned here, noting that G5 was 20/20 but G6 was 30/30.

Unfortunately it is true that Dexcom has switched to a 30/30 rule for the G6 as opposed to the 20/20 rule for the G4 and G5. That is horribly disappointing to me but is fact as can be read in the Dexcom User Guides. However I disagree that one should only calibrate if outside the 30/30 range but I do understand that is what the User Guide say

1 Like

I’ve had this happen with 3 or 4 sensors so far. After warmup, it makes me calibrate twice (!). Then every 24 hours afterwards if you don’t do it before then. These sensors aren’t working as designed (no fingersticks!) and you can call Dexcom support to get a replacement.

Oddly, I find these “buggy” sensors actually last longer than the “normal” ones—usually 8 or 9 days in my experience, sometimes 10, and they’re still accurate even if not working as designed. It’s good to have a few extra sensors around since some will only last 5-7 days, so keep using the one you have to calibrate daily so that you can stockpile replacements for the inevitable failures. Welcome to the wonderful world of Dexcom!

There’s no way I only calibrate it if it’s outside their acceptable range. I calibrate it if it’s off more than 5 points within 10 minutes of comparison. I want mine to be within 5 points of my favored range. 95-105. But I always wait to do the fine tune calibration until I am in that range.

This exact thing just happened to me on my present sensor. I don’t pre-soak, but when I inserted my new sensor after the two hour warm-up period, it asked for 2 calibrations. When I told a Dexcom representative about it, she explained to me that sometimes when you enter the sensor code, it doesn’t “take” and you will be asked for those initial two calibrations, and then one each day for the rest of the 10 days session (if it lasts that long for you - it doesn’t for me!) She offered to replace the sensor if I didn’t want to be bothered with a daily calibration, but I declined as I usually calibrate once per day anyway to make sure my sensor is semi-accurate.

I find that when you do a calibration it instantly splits the difference, as you say, but then the next actual reading is much more closely in line with the calibration value. So I wouldn’t do a second calibration until I’ve seen the next number.

2 Likes

I’ve used Dexcom cgms since the early days of the G4. Since starting on the G6 last March, I’ve had only four sensors last the entire ten days. Every other one has failed after five to eight days. Sensor errors in which there are no readings become numerous and long lasting. When the readings do come back they are very drastically incorrect (i.e., cgm reads 69 and a fingerstick reads 189. Many are worse.) I’m doing more fingersticks than any time since I started using a cgm. Once a week I have to call Dexcom support (sometimes waiting as long as two hours) to get the failed sensor replaced. I have a support ticket from 8/3/20 asking why most sensors fail, but it has remained unaddressed. I’ve asked about it every week when I call to report a new failed sensor. Best response I can get is that “they must be busy”.

Lately I’ve had numerous sensors requiring calibration after the two-hour warm-up despite having input the correct (without a doubt) sensor code. Then every 12 hours I have to re-calibrate. Many calibrations also fail.

Since Dexcom had a new CEO about five years ago, quality control and support have been atrocious. This used to be a good company, but now it’s just downright dangerous.

I can’t reference the G6 because I am using the G5. However I have at times experienced what I considered to be great variances between a blood stick reading using a highly rated blood meter and the current Dexcom device reading. I have called Dexcom on occasion and shared my concern re the differences. Dexcom has said that they consider differences of up to 20% to be normal and acceptable. I have experienced occasional differences of of 20%, 30%, 40%. Even 20% sounds like a large difference to me, but apparently not to Dexcom. I don’t bother calling them anymore because they don’t have an answer other than to try testing again. I’m surprised you experienced that because I thought the next generation G6 was going to provide a leap forward in ongoing accuracy.

I concur with all the suggestions about only calibrating when you are both in your target range and it is not going up or down at the time.

My experience with G6 is that 4 out of 5 new sensors are really inaccurate for the first 24 hours; often it is ridiculous. So I just follow the G6 Manual’s advice that says if the reading does not jibe with what you feel, then calibrate. So during the 1st 24 hours of a new sensor, I calibrate at least twice and may have to calibrate 5 times. But after that first day, it is wonderfully accurate. I still calibrate it once or twice in the next 9 days.

When I calibrate (again, only when stable and in range), I first wash my hands thoroughly, then take 2 meter readings. Normally I enter the first reading, then for the 2nd (which is what will be the resulting G6 reading) is the average of the two meter readings. G6 wants to average its reading with your calibration, but during the first 24 hours, its reading can be way off and my meter is much more trustworthy.

This is way easier than writing about it, and after the first day, I am very pleased with G6 accuracy.

I should say I normally re-use the same sensor another 10 days, partly because I can avoid that horrible first 24 hours. This way I get 19 good days out of 20. So far my 19th and 20th days have been just as accurate as days 2-10. I see no accuracy drop-off at all when reusing a sensor once.

I know every body is different, but for mine, that first 24 hours of a new sensor is really and sometimes dangerously inaccurate. But I love my G6, now that I’ve learned to deal with it.

2 Likes

George49 – I one time did a test of meter readings – 5 at a time. They were usually within 5% of each other and worst case, 10%, so the average was about 7%. I think 20% is unacceptable.

As long as you have the G5, I would be sure to meter test whenever the G5 reading does not match how you feel. I got a lot of value out of my G5, but it is true I leaned on the meter whenever I did not trust the G5 reading.

My G6 is much more accurate, in case you are able to get that version some day.

Yvonne1 – It is good to share experiences here. It reminds us each of us is different and devices and meds work differently for each of us.

My only advice is 1)before installing a new sensor, make sure the skin is clean and dry, no soap residue, and 2)after installing a sensor, try covering the white adhesive that is part of the sensor with a larger patch made just for Dexcom sensors. I use FixiC Patches. This protects the entire sensor area and possibly keeps it accurate longer, at least for me. Know way of knowing if it would help you, but you might give it a try.

I never calibrate. You can increase the variability of the readings by errors in the finger stick

Try leaving it alone and you will likely see better results. Works for me. A1C in low 6’s

Also I never “Pre-soak”

I work in the measurement business and also find in industry that errors can result from over calibration

The errors of the calibrating device is added to the error of the measuring device. I have learned to trust the Dexcom and rarely if ever use a finger stick

I do double check it against the blood lab results and usually find it within a few points

1 Like

I just started on the Dexcom G6 this past week as an upgrade from the G5. During the first week, I have been wearing both the G5 & the G6. For this first run, I did not presoak the G6 contrary to the G5 which I always presoak for 12 hours. After 2 hour G6 warmup period, I was thrilled to see my first G6 reading at 78 which matched exactly my G5 reading also showing 78. Within the first couple of hours, the G6 meandered a bit and was generally a little lower than the G5 but after about 5 hours, the G6 started reading higher by 12-13 points and has remained at that level each day thereafter. The G6 is a lot more stable than the G5 which loves to give wonky readings, especially when BG drops below 65. I still do fingersticks every 12 hours to calibrate the G5 but have not done any calibrations yet on the G6. So far, the G6 appears to be a big upgrade from the G5, especially for me as I like to keep my BG’s around 60-65 which drove the G5 totally crazy

2 Likes

Why so low, you have no room to go lower. I think 90 I’d perfect for me. I feel low when I’m under 70

I typically calibrate 2-3 times/day, to support FNIR. Depends in part how the sensor is running. I’ve noticed that after 12 hours or so, my sensors tend to return to the same difference. That is if low by 15 and calibrate, then returns to about 15 low. Not calibrating or at least verifying the first day seems a little risky to me. Many of my sensors are off enough at startup to result in high or low BS and a few have taken off on excursions.

When I fast for a couple of days (No food and no insulin), my BG totally flatlines between 65-67 mg/dL so I figure that is my ideal baseline BG for my body and that is the number I shoot for and am comfortable with. I don’t even start feeling low until I drop below 58 and still function fine in the high 40’s. Where you feel low, for those of us that do feel it when we go low, depends on where we run our average BG.

1 Like

For ME, if I don’t feel a hypo that low, then it’s because I’ve run a long string of hypos and have lost all hypo sensitivity. That’s not where I want to be.

You might also see some of my past discussions with mohe001 where he/she wrecked a car while hypo and then bragged about how competent they are when skiing and driving with very low bg’s.