Dexcom has been inaccurate lately

On my last sensor change I had 4 sensors fail on me in a row. I have never had a problem with dexcom before in the last 4 years since I have been using it. My sensor was saying I was 11.6mmol when I checked with my meter it said 9.1. This has happened alot in the last week. I even try to insert it before it expires to give it better accuracy. Maybe I just got a bad batch, I don’t know. These sensors have to be more accurate if an insulin pump were to give me a correction. I am losing my trust in it.

Dexcom will swear otherwise, but we had a run of apparently bad sensors (inaccurate, drop-outs with “???” and BG appearing to run away high or low despite his actual BG being stable) and early sensor failures last year, suspiciously after starting a new transmitter. Dexcom swore it couldn’t be the transmitter and kept replacing sensor after sensor that didn’t last a week, causing endless frustration and distress for my son who hated insertion. Lo and behold the transmitter failed at a little past one month old, and on the new transmitter there were no more “sensor” problems.


Wow! When I called them I almost felt like they were accusing me of not knowing what I was doing. Needless to say, they are going to replace them. When my sensor goes from 6.0 to 9mmol in a short time when the is mo food or insulin on board I know something’s up. Out choices are limited when it comes to cgms. I hope things get better. I need this to be accurate to know that I am safe.

I am fairly new to Dexcom. I started the end of June. At first it was great. after my first month, I started getting weird readings, a lot of loss of signal, false lows, etc. Every time I would change the sensor, I would have about 18 hours of crazy readings that were 80-100 points off from a standard glucometer. Dexcom didn’t really have any answers for me. I spoke to my endo educator last week and he suggested a complete change in site. Since I take 6-8 injections daily, he thought that maybe I was developing scar tissue that was interfering with readings. I tried that 2 days ago. Perfect sensor change. Readings were off by 2-13 points only. No issues.

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Maybe on my next sensor change I will try a different area. I use my arms and don’t normally have an issue. I try to use my stomach for site change for my infusionset. We’ll see. I’ll give it a try.

My educator suggested using the thighs as an alternate site.

I have used inner thighs for many years with G4, and now G6 with good results.

Also important to stay hydrated.


Bad sensors come in runs, like Dylan_Sutton says. This leads me to believe there are manufacturing problems or temperature storage problems.

If you get a couple bad sensors, there is a higher probability that you will get more bad sensors. Next batch should be fine, but you will need to keep close watch on these ones. Check manuals. Run in calibration mode - ‘no code’ mode when you start the sensor.

Is it accurate there? Is one area more accurate than the other? I would think that as long as you are hydrated well it should be okay no matter where you insert it.

It seems to work best wherever you’ve got a little fat. That’s how really, really lean people figured out arms were a good site, because even the skinniest person can usually “pinch an inch” on the arms. Wherrever you’ve got a little (or for some people, a lot) of padding is fair game. Whether it be belly, butt, arms, hips, thighs, breasts, calves, etc…


Right, thankyou. I seem to think that because I wasn’t hydrated have might been the issue. Last night I corrected a high and it didn’t go down. When I checked my graph I stayed high from 130am to 445am. My high is set at 10.0mmol on my dexcom. I suspected that I had some ketones so I checked and it was a small amount so I drank 2 glasses of water to flush the ketones and when I awoke I was 5.3 and my dexcom was spot on. I am going to try a higher basal rate through the night as this wasn’t the first time it’s happened in a week.


I’ve been having this issue lately too!! I never had it before and been using this around 1.5 years. I’ve had to calibrate and sometimes, it just got worse. I wasn’t sure what to think especially because everything was fine for 1/2 day to 2 days. It’s causing problems especially because my pump is shutting off thinking BG Is going low and when I did a fingerstick, it was definitely the opposite

I’ve always HATED calling Dexcom and some techs are better than others. I’ve had rude ones but most are helpful. I hate holding bx it typically takes awhile and if I do call back, I often miss the call!!

Dexcom was doing extraordinary well in stock investments but recently took a downward hit and projections are iffy.

The freestyle libre 2 is a great competitor now and easier to get covered by insurance. In addition, I think in the UK? You can buy the equipment OTC too.

It’s challenging that we Dexcom users and add pumping too have to order direct or use a specialty pharmacy when the newer products that are becoming more pump friendly are carried by big box pharmacies!

Right now, Dexcom and tandem have both partnered with other promising companies to expand their products etc

Anyways, given several complaints here on the forum and not at all typical, makes me wonder if the stock turn is leading to trying to dump off iffy equipment!! Hope not but capitalism anf all!! I’ve always noticed that once you have these devices, it’s harder to get customer services or find info you need as a user vs prospective buyer. I understand to a degree but STILL!! I’ve given them this feedback …

I do see some site improvements and I’ve heard they are working on the weaknesses on the website and getting accurate assistance easier.

I’m planning to call Dexcom because this issue plus loss via medical procedures have led to loss of 6 sensors and I want replacements.

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I have not (yet) run into a bad batch of sensors, but after reading these posts, I plan to keep that in mind if I have problems in the future.

What I have been running into, about 4 out of 5 new sensors, is inaccuracy, sometimes 25% too high or low) during the first 24 hours of a new sensor. My way of dealing with that is to use a meter and re-calibrate until it is clear the sensor has settled into being accurate. Once that happens, I am quite impressed how accurate the G6 sensors have been during days 2-10. (And since I sometimes restart a sensor and use it another 10 days, the accuracy continues during days 11-20.)

The important thing is right in the Dexcom user pamphlet – if the Dexcom measurement does not match what you feel or expect, check your meter and re-calibrate if necessary.

Overall, I can overlook the first day problems and am happy with Dexcom G6. But perhaps I have just been lucky, so I will remember these posts in case I get a bad batch of sensors.

I find that its sometimes doesn’t catch the highs and then sometimes my meter will say higher than dexcom. It usually catches up as I know ther is a 15m delay. The last couple of days I have been testing more with my meter and comparing itto dexcom. I find that it has been almost spot on especially when there is no food in your system.

When it’s working well it’s terrific. I got a bad batch too - transmitter failed, sensors failed, which meant I had a week of poorer control. They did replace it all, customer support was pretty good. I plan on badgering my HMO to pay for backups for everything so I don’t have to go back to finger sticks again.
One reasons I’ve had failures that might not have been Dexcom’s fault: I hit a vein when I inserted it and had a bloody mess that I didn’t discover for hours when the thing failed.

I’ve been a Dexcom user for many years, since the beginning of the G4. Both the products and the tech/customer support used to be very good. However, since late in the G5 product life cycle, and even more so in the G6 product life cycle, both the product quality control and the tech support have been abysmal. I started the G6 in March of 2020 and have only four sensors last the entire 10 days it is purported to last. While Dexcom replaces each failed sensor after 5-8 days, they refuse to even discuss the reason for the failures of nearly every G6 sensor. I’ve asked tech support each time a sensor has failed (basically once a week since March) for the reason they have failed so consistently. No response from Dexcom. I even logged a tech support request online on August 3, 2020 asking specifically why nearly every sensor has failed. They have not responded. Every time I report a failed sensor, I ask why they continually fail and why my support request has not been answered. The answers I get are “I don’t know.” and “I guess they must be busy.” I know that the CEO was replaced about 5 years ago, which corresponds to the beginning of the horrific number of product failures and the equally horrific support. I am a stroke survivor and rely heavily on my cgm, but after 5 days I cannot trust my Dexcom cgm for ANY treatment decisions. I’ve been doing more fingersticks with my G6 than anytime since I’ve had any cgm. Since Medicare will not pay for both a cgm and test strips, I have out-of-pocket expenses that I cannot afford. My health (and my life) are at risk because of Dexcom’s lack of product quality and support. Dexcom has gone from one of the best medical equipment companies to the absolute worst. Does anyone know of a better product?

I would think so (re: location of sensor), @Dee_Meloche, but we always gotta remember that it is only FDA tested for the abdomen. So, I guess I never really considered that could be a source of error, but its possible. I always put it on my hip, never on my abdomen. I do get much more error than some of you.

Where do the people with really low error place it? Let me track down someone with really low error and ask them…

Hey, @Marie20, what are your thoughts on sensor location on the body and that as a possible contributing factor in the error some of us see from time to time? You always have such good accuracy…wondering about your perspective.

I was just about ready to ask if anyone else was having this problem as well?

I too have been having problems with my G6. Up until about two months ago the sensors started failing about seven days in. The readings would error out for about 3 hours and the cal was off after that. I’d try a recal and it would go back into error.

Each time it failed after 7 or 8 days of use I called Dexcon to get a free replacement sensor, sometimes they try to kinda get out of it but I keep pretty good notes and didn’t hesitate to mention what and when I noted a problem. I was firm but nice to them. I still keep a daily log in excel with 9 or 11 readings through out the day, I record what I eat and record the two insulins intake. I also note any G6 issues including when I change sensors and xmitter, and record the four digit code of each new sensor and xmitter.

It works great about 70-80 percent of the time and apparently that seems acceptable or within spec with Dexcom. I don’t think the new style xmitter works as well and there must be an issue with their sensors along with that. For the price of the equipment, we should get our money’s worth! I do pre-soak for 12 hr prior to changing over the xmitter.

Does anyone know if the separate portable Dexcom monitor or X-drip may work better or be more stable than the Android phone app? I do indeed like the Dexcom product - when it works which is the vast majority of the time! With these issues I glad that I still carry a spare stick monitor with edibles for lows about everywhere I go - always be prepared!

@mohe0001. I always wear mine on my upper arms. I’ve never tried it anywhere else as I keep my abdomen for my pods. I think placement might matter for the sensors. I remember someone with a Libre in 5 different places and as he tried each spot he did a short blip on a video about accuracy of each area and there was a difference in some for him. Not a foolproof test as it could have been a sensor working better than another one but it was interesting. He very definitely said there was a difference in some of the areas.

I see no reason there would be difference between the Libre and a Dexcom in placement.

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I also agree with you that the location of the sensor is really important.
I will watch this video carefully and hope to let me know more.

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