Dexcom Innaccurate to a large degree?

Hello Everyone,

I have had my Dexcom for only one day and several hours. I went to my endocrinologist for help with putting the first sensor in and instructions etc.- it's in my right middle abdomen area.

I've had several readings which have been from 40- 59 points different than the blood glucose finger sticks as well as incorrect. I can tell when they are wrong on Dexcom right away- the lows and higher readings are all wrong. I'm spending too much time calibrating Dexie.

The last one just said I was 49 and gave me the below 50 alarm, the finger stick was 109.

Should I try another site? I'm not sure what to do. I also think something is wrong with my receiver as it doesn't always seem to vibrate/beep now with warnings all of which have been low.

That is a large part of why I wanted cgm- I have been having low lows and I'm worried about this when I'm sleeping, but none of Dexies readings so far have been correct for that. The other part is to see what is happening all of the time which I can't possibly do with finger sticks alone.

Will this get better? Am I doing something wrong? I'm wondering if after another try with a different sensor/location I should send this back and wait for the new and improved model?

First day is off. Do not calibrate more than 2x/ day as sensore gets confused. . site is fine.

It will get better, definately a little off for the first day or so, then it settles out and becomes invaluable:-)

The longer it's in, the better it is. It seems to need to 'marinate'. Bet you'll love it in a day or so ;)

Take a look at calibration advice in Beyond Fingersticks from Will DuBois. Calibrate when BG is stable, not changing rapidly, 2-3x/day. Don’t correct your Dexie when it’s behind - the sensor will lag when your BG is changing. Use the trends: if you’re 100 with two down arrows, fingerstick and intervene!

The better I do my job, the better Dex does its. If I calibrate at a bad time and throw it off the first day, I stop the sensor and restart it for fresh calibration. Good luck! It can be frustrating but is also a great help.

I like Jrtpup's advice...Let it "marinate". I had to call Dexcom at least 3 times my first few days, give them a buzz and explain (in detail) what had been happening. Their advice will be similar to everything said here...and will probably do great things for your confidence!

Look at chapter 10 of the manual - it gives you a good idea of what kind of accuracy to expect. It is eye opening.

Especially see Table 2 - the hypoglycemic Alert Evaluation.
You will see that with the alarm set 80 mg/dl, the true alert rate is 64%, the false alert rate is 29% and the Missed Alert rate is 36%.

I'll say with most sensors , I get decent results... within 20 mg/dl or so. I've had one sensor so far that was kind of flaky and it died early. Dexcom replaced it. The first day is flakier and tends to jump around.

Be sure you do not take Tylenol or other acetaminophen containing products as these screw up the sensor.

I'm on day 2 1/2- had another false low reading, which didn't wake me because I sleep with earplugs, but I'm only calibrating now when it asks. I will see how it goes, but I'm not sure this is for me. I'm also having pain from the sensor and although I haven't taken any yet, I do need to take pain killers with tylenol at times. I'm on warfarin now and I wonder if that could affect the cgm at all? I guess that would be in the literature also. I will read chapter 10. So far all the low readings and high readings have been totally off by a huge margin so maybe it is this sensor, I don't know.

Thanks for your help!

Hello Everyone,

Just to let you know I called Dexcom- they had me calibrate it 3x 15 minutes apart... I had 3 readings of 95, 93, 92 for that, then Dex jumped back down 2 seconds later to 50 then 57 and then 40 in a very short period- so I called back and they said to stop the sensor and remove and they will send a new one. However when I removed it, the reason for my pain is obvious, I have a red, painful lump now from the sensor... I hope this isn't an infection starting.

I'm not sure what to do now- if I should just give up on the whole thing or try another one somewhere else.

This also means I probably won't tolerate a pump which I wanted to try at some point:(

The rep I spoke with said I was correct to calibrate when there was huge error btw, so that is what you're supposed to do when that happens in case anyone else is wondering.

I always do that. Sorry to hear you are having so much trouble. Perhaps the inflammation is part of why it isn't working well.

I wouldn't assume that you will have the same problem with a pump just yet... or with the Dexcom. Probably worth trying with a new sensor in a new site.

PS. I've noticed the last few days that resting a hot laptop on the sensor makes it drop rapidly...goes away when you the laptop is

thanks hpnpilot-

me too :(

I had high hope for this- I felt like it was going to be my new best friend and I felt safer going to sleep- but I hated that sensor as soon as it was in me- my body doesn't like foreign objects... there has to be a better way to do this... my brother said there is a cgm which is in trials now in europe which uses lasers so maybe that will be one I can use at some point hopefully if Dex doesn't work out.

I may try another one on my thigh later tonight or tomorrow and give it one more try.

That's funny about the laptop- I wonder why the heat would do that?

Maybe the heat speeds up the chemical reactions that drive the sensor...not sure...

ps. I won't give up on a pump yet because I know some of them use jets, so maybe I can use one of those...

yeah maybe..

Don't give up on it yet. I've become a huge fan, even through some of the issues you're experiencing.

From the description of the pain and the redness, are you sure you didn't maybe go through the skin and hit a muscle? I did that the first time I tried to use my thigh. If you're going to use a site without a significant amount of fat below the skin, you have to make sure you pinch the skin up when you do the sensor insertion.

I've found the best spot for me is the back of my upper arm. After the first day or two, my results really settle in and match my meter (one touch ultra) very well. With some skin-tac and Opsite Flexfix I can also usually get two weeks out of a sensor.

Once you get a sensor to stabilize and get to see a whole days worth of readings (288 data points) for 2-3 finger sticks, you'll be hooked like the rest of us.

Hope you keep up with it and don't be afraid to keep posting on the site and asking for help. There's a lot of great people and useful information around here.


Hello Alan,

I didn't do this completely myself because it was so awkward and I could barely see what I was doing, the nutritionist/pump trainer at my endo injected it and there was a pinch from the needle- it was in my abdomen- I don't have a lot of fat right now as I lost 15-20 pounds prior to dka etc. I don't know if this hit the muscle at all, but it didn't seem that painful at first to have done that. We did pinch the skin up as far as I remember but I will make sure to remember that.

Then it hurt for a few hours and seemed to get better and then worse with some activity yesterday and today it was hurting more again- I'm just glad this thing is out of me, I feel much better now. I hate iv lines and blood draws also as they are painful for me. I think the redness and inflammation are my body's reaction to this unfortunately. I'm taking a day off and I may try another area tomorrow.

I'm not good with doing injections etc. although I had to do lovenox injections recently myself, that was really hard for me to do, but this is very awkward and everything is much bigger than I imagined- the sensor is a lot thicker than 2 hairs imo.

I may try my arm or leg tomorrow and I will let you know what happens, first I have to see what is going on with the inflammation.

I would love to have all of that info for sure, but not if I have to feel I have something hurting me all the time- it's not worth that to me.

I am very thin due to 55 lb weight loss just before and after diagnosis. I too had trouble/pain with the abdomen sight.
I saw the suggestion on this sight to try a thigh sight, and I gave it a try.
The pain/discomfort of this area is nonexistant, I even found myself reaching in my pocket and brushing the sensor, and saying "oh yeah that's my sensor to myself.
I am alergic to the Dexcom adhesive so I have used IV3000 and Flexfix to lay down as a barrier, before I insert the sensor.
I placed the sensor on the upper thigh, I pinched up a little flesh and inserted the sensor with the "fall" of the leg toward my inseam. I made sure the angle of the inserter matched the angle of my skin so as to keep the wire just under the skin and not touch/pierce the muscle.
I am on day 9 of this sensor and I still have had no pain or discomfort from it, I have gone swimming, I have led a 100 mile bike ride, and several trips to the mountain bike park.
I must say it took a couple of failures before I worked out the kinks, with the help of everybody here and help from Dexcom local rep.
Don't give up it will get better.
I believe I would also need a pump soon, and like you thought this would be a good test run for an insertion sight type of placement.
I believed as you did that it was just not for me, but the tudiabetes encouragement got me thru, now I know I can handle it and I have a fantastic support group here:)

Great to hear the dex is working out for you Par! I wouldn't be without mine now. Despite a couple of days of frustration each time a new sensor is inserted, I love it.

I've never had pain/redness, so I think it must have somethng to do with the site or insertion. Do try a thigh site.