Bad Experience ... Any others?

Lately I have been finding that dex comes in two flavors .. acceptable and not acceptable. The latter is when large corrections have to be made.

Last Monday I had breakfast at about 6:00 AM, went to work and had a particularly intense morning. I kept my eye on the dex readings but did not do a meter test during this time. At about 12:00 (noon) I went to work at home. While driving I began to feel really bad and when I got close to home I started to feel chest pains which I at first attributed to soreness due to upper body exercise the day before. Then I started to think that when I got home (I was close) I would call 911.

Throughout this driving experience I kept my eye on Dex which pretty much read about 180 the whole trip. I had tried to correct this a few times during the morning but the number remained steady.

At home at last, I checked my glucose (Dex reading still about 180) and the actual reading was 450!! Yikes! I never was that high. I immediately thought that the meter was wrong, but it was correct. I decided to quickly change the infusion set. When I took my shirt off I found the entire infusion set had fallen off (adhesive failure, I guess) and I had not been receiving any insulin since early morning.

DEX NEVER NOTICED!!! I changed the set and gradually came back to normal.

My four previous sensors had been pretty poor. Two, after some short time, gave ERROR 1, which is fatal. Two were just as erratic but never gave the notice. So, four bad sensors! I called Dexcom and spoke to a customer service agent who wanted the lot number, etc. which I actually was able to give him. He then went through a test to make sure I understood how to use the Dex even though I have been using it for about 3 years with no issues. He admitted I was doing everything right and sent me two sensors, but not the 4 that I wanted. He treated me like a moron (or a child) even though I have a PhD in physics!!

So, I think DEX almost killed me!! Anyone else seeing wild swings in senors (corrections over 100 points) or Error 1s? Or, perhaps, I am a moron.

Some time bad I did have some issues with a few sensors (we all have) but I called the sales agent and asked about it. With no hesitation, she sent me a free box of sensors. I wonder what has changed with Dexcom.


Yes, I have seen poor sensor performance occasionally. The kind of really bad experience you had I have not had too often. I have had a couple of error 1's when the sensor was so far off from the input fingerstick value that the Dexcom gives up. After trying again 1 hour later, if it doesn't recalibrate, I call it in and they replace the sensor.

You simply should not rely on it as your sole source of glucose data. Definitely do not use it to dose insulin. It is only a supplement to fingersticks. I still do fingersticks 10-12 times a day. And especially before driving a car or other critical tasks. The technology just still isn't very good yet.... perhaps the generation 4 sensor coming out soon will be more reliable.

I agree with you - some sensors just seem flaky from the start. They need to tighten up their manufacturing processes.

No. I never dose or drive based on Dex. But I did think I could rely on it for changes. Usually I could. Perhaps I should keep my eye on Minimed's sensor.

You didn't mention when you last calibrated your Dexcom. I know most of us at one time or another have bolused from a Dexcom reading alone, but it is not something you should do regularly. How close was the Dexcom sensor to your infusion set?

It was at least 6 inches away. You are correct that I didn't calibrate the thing but I didn't dose based on its reading either. For most of the morning I was just so busy and in a public space that I couldn't do a calibration. But even if it is off, being 250 off is HUGH!


I had a lot of inaccuracy with dex also, not as bad as that- I think the biggest difference was 120 points or so. I woke up on one occasion with dex saying 169 but I was 53!!! I got dex mainly for low alerts.

I don’t feel it is acceptable to have that kind of error range or to have to wait two days for a sensor to work properly. Dex can’t handle ups & downs at all IMO. On another occasion It did warn me of a low but it said I was going even lower- I took too much sugar & spiked up a lot which I wouldn’t have done most likely with a series of finger sticks.

I also found the trends were not correct a lot of the time. The alarm was constantly going on when there was no problem. The adhesive gave me an itchy rash and the sensor was painful & caused swelling & inflammation. The sensors were really awkward to insert.

I gave up after two sensors & returned it. My educator agreed with this decision. I do hope someone comes out with a better & more reliable sensor/ monitor at some point.

There is one in trials in Europe which uses laser technology- I hope this will be pain free & accurate- if it is I will buy it myself because I do need cgm. Even if Dex had optimal performance it was just too painful for me- & I think using latex or anything that causes allergic reactions in a medical device is crazy.

I think you should call them back to complain & get your other sensors.

If you have symptoms like that again I would pull over & test/ check everything out. I think I was doing more testing with Dex than without.

I forgot to add that one of my sensors was on for four days and it made no difference to the accuracy, the other I removed after two days because it was giving me a migraine- that one was in my arm. I called Dex about the first one and they did the same things they did with you... then they sent me a replacement.

I always tested before any meal, insulin use/ correction etc. and after. I never trusted Dex to be accurate- at one point when I was on a walk it told me I was jumping up to 224 and I was at 93 when I got back... I was only in the low hundreds I think before the walk.

I think the pain was the main factor for me that made me say forget it.. I had no problems returning it with Edgepark, although they did take forever to get an rma number, they were very nice and sorry that it didn't work out for me. I couldn't return the sensors though.

Here is a link for the other device I mentioned- let me know what you think about it...

I agree I don't understand how it can be that far off, anything over 10-20 points renders it useless imo. when my bg was steady it had maybe 1-2 accurate readings per day on a good day. I think your experience overall must have been a lot better than mine since you have stuck with it for 3 years so maybe there has been a change in the sensor quality?

I get my sensors in packages of 12 (for 3 month, which lasts me 5 months).

My last shipment was amazing. Almost every sensor was always so accurate.

Recently I received a new shipment. My first sensor from this shipment was off by more than 30 at every calibration, and sometimes much more.

What worries me is that my second sensor is the same. And I am afraid that all of the sensors in this shipment will be inaccurate.

I have found that the lots are very variable and if one sensor in the lot is bad the others can be as well, although not necessarily. Lately they seem to not like sending replacements for bad sensors even when they try to kill you. I think the J&J association is a bad thing.

I use the Animus pump and I hate it but I liked the MiniMed. (Long story posted elsewhere). I wonder how things work with their sensor and if improvement could be expected so they compete with Dex. If so, I will switch!


I've had occasional luck restoring Error 1's, entering a fingerstick after an hour. More often than not, though, SE 1's are indeed fatal.

If you read my 3.75 year update thread, you'll see that I share much of your frustration with the Dex. Variability of performance is hard to take, week after week.

I haven't had the same experience as you with replacement sensors, though I only call with individual sensor problems and not batches.

very curious indeed.

the attitude shown you is even more heart stopping and I would offer unacceptable.

thank you for sharing and best wishes to see this resolved.

Some people have said the first 3 days of a sensor is typically pretty inaccurate. I plan on testing that. The frustrating thing for me is I used to use the Navigator, before we US people couldn't get the sensors anymore, and pay out of pocket. My insurance co pays for the Dex sensors, but I would rather pay the $400/mo for the Navigator.

On Tuesday, I had somethign unusual for breakfast so my bg went high. Then I corrected. I was up near 200 when I entered a correction, from by fingerstick. The CGM was flat all morning around 100. I took some insulin. I started to feel low later, but for some reason, Dex indicated my bg was raising adn I was at 346. I did a finger stick and I was acutally at 84. I was dumbfounded. I don't get it and I get really frustrated. I then get mad I can't have the Navigator anymore.

Sorry, no explainations or suggestions, just sympathetic frustration.