Frustrations and trouble with Dexcom CGM

i am relatively new to my Dexcom CGM (5 months now). i LOVE it, BUT, i have
more than just occasional problems with my sensor/transmitter readings.
does anyone have any of these problems and if so, what do you do about it?
1) inaccurate readings (more than 30 points off)
2) missing direction arrows
3) question mark icons (top right corner on transmitter screen)

i am very lean, so i have difficulty finding a "good" site on my belly to attach my sensor, but i do have enough to attach it correctly.

Dexcom is a fabulous company and always replaces my "dud" sensors, but i still get very frustrated taking one off and changing it for another.

Usually I calibrate and wait. Admittedly, I don't get many ??? and when I do get those I usually just change my sensor.

Also, I would check on your transmitter battery. From what I've experienced, as the battery starts to go so does the device's accuracy. As they're "supposed" to last about 6 months with the G4, you may be getting close to the end and it may soon be time to order a new transmitter.

2) missing direction arrows

A question from someone who usually follows the Dexcom discussions from the sidelines. (I don't use the Dexcom CGM)

I'm not quite clear on what you mean by the direction arrows being missing. Wouldn't that just mean that there is no trend which the firmware considers is pronounced enough to post a directional arrow? Is a direction arrow always supposed to be visible on the Dexcom monitor?


There is always an arrow. It is either pointing horizontal (no fast falling or rising) or slanted up or down for rapid rise or fall.

From the Dex site:
The question marks mean that the receiver does not understand the sensor readings for the moment. You will want to wait a minimum of three (3) hours for them to clear. If they do not clear within that time frame, please contact our Technical Support team at 1-877-339-2664 for further assistance.

I rarely get the question marks. Usually, they clear up within a half hour if I do get them. I don't know how much subq you have on your arms but I alternate the inner/front part of my upper arms, vertically. That position on the arm means I don't press on it when on my side and it is not taking up my pump insertion sites on abdomen.

I try to wait at least 4 hours after a new insertion to start the dex. Just to give it plenty of time for the insertion tube to get moist from tissue fluids.

If you do everything right, has anyone suggested it could be the receiver itself rather than the sensors? But first, I would review technique.

I've experienced times when the direction arrow disappears as well. I interpret that in a way similar to the ??? display. the system is not sure what to make of the direction as it tries to make sense of conflicting information. The missing arrows do reappear.

the direction arrow is always supposed to be present. when it is missing, it is because the sensor and the transmitter are not receiving information to and from one another.

thanks, neil. i am actually, within a 5 month period, on my 3rd transmitter. my 1st two were dysfunctional and it took over a month to figure that out with all
the "Tech Support" from Dexcom. i think that most of my problems are related to my weight. i have relatively no body fat, although i am able to pinch up some skin to insert my sensors. i rotate sides from my pump site to my sensor site.and, i try to coordinate my resevoir dates as best as i can. thanks a lot, Daisy.

Hi Daisy Mae,

I have all of these problems too, frequent numbers more than 30 points off, no arrow and question marks. Lately I have been having more irritation with the sensors so I wonder if it is that? I also thought maybe it was my transmitter since things seemed worse lately. I have just started with a new one as mine was 6 months old and I will see how it goes with the new one.

First days of the new transmitter and a new sensor and I still had the same stuff happening. My experience is that Dexcom often isn't very good when bg is moving fast or at all or if I take insulin for food or corrections etc. but then at other times it is very good.

Often when I'm at my wits end with it, it suddenly reverts and gives me hours of good numbers or correct trends etc. I usually just wait the ??? marks out and then it goes back to normal. Even with all of the dexcom flaws that I experience it is still better than not having it at all.

I'm having some of the same problems. I wouldn't call myself lean, but small so not much area for infusion sets & sensors.

When I had lots of ??? it turned out I didn't have the transmitter clicked in properly, when I managed to click it in things improved.

Yesterday I had a sensor give up after 5 days, ???? for 3 hours after intermittent ones & lost directional arrows & hour glass. They are sending me a replacement. This was on my stomach where I have plenty of padding. The next sensor I put in my hip, & I did pinch up the flesh. But it is going all over the place, & not really matching the meter. Overnight it was lower, today it is higher? I'm giving it until tomorrow & then I shall call Dexcom again.

Are you taping down your sensors? Are you using Skin Tac or a similar adhesive? Keeping the sensors from moving around is essential. If the electrode starts to work loose, the readings will be unreliable. This will elad to premature ??? and missing arrows.


Hey Daisy - we've all experienced these hiccups with our Dexcom's. When I first got mine, I drove myself crazy because I expected it to be within a couple points of my meter every single time. My experience (and you may have heard this before) is that the sensor calibrates much better after being in a couple days (although I did read one user's experience a little while back that stated her Dex was most accurate in the first 24 hours of insertion). Also, as "meee" points out below trying to calibrate with fast moving blood sugars (after meals, exercise etc) is typically not good for accuracy. I always try to calibrate or insert a new sensor when I know my blood sugar has been/will be relatively stable for over an hour. For example, I often insert a new sensor before going to bed and then I'll do my initial calibration when I wake up in the morning.

I don't think I've seen the "no arrow" on the display issue, what was Dexcom's response to that? Also, when I get the ??? I'll just let it ride out for a couple hours and see if the Dex can self correct and most times it does.

Quick question - have you tried to leave a sensor in for more than the recommended 7 days? Most times I get 20+ days out of one sensor.

Good luck and hopefully you get these things worked out!!!

I sometimes see the "no arrow" on the display. Typically if the readings keep changing direction (e.g. 10 mins rising followed by 15 mins falling then rising again). This is often near the end of the sensor's life. I use my Vibe as the receiver - I assume that it is unable to decide what the real direction trend is.

I can give you one hint to avoid inaccurate readings. My first day of sensor use, I calibrate my Dexcom more than once, once when I am lower and once when I am higher. I often calibrate the Dexcom throughout my sensor use multiple times a day. It seems like a hassle but I find it to be more accurate through the day/night.

I've started using Skin Tac on others' advice. It certainly stops the tape from starting to peel up. I've read if one tapes down the sensor you should put tape evenly on all sides. Do others find this to be true?

I use the 4 inch wide Opsite Flexfix tape. If you cut a piece around 2.5 inches long it will fit nicely across the sensor (i.e. if the sensor is horizontal, the direction of the roll of tape would be up/down). I then fold the tape gently in two parallel to the long side and using an old sensor as a guide, cut out a rectangular hole just large enough to clear the transmitter bed. This will mean that the sensor is evenly taped

Daisy Mae, simple suggestion: Try some other sites. Ignore Dexcom's instructions to only put it on the stomach. They simply didn't want to incur the additional cost and delay to get other sites approved.

I wear it on the backs of my arms, and get outstanding results. For people with low BMI, the tricep area often has just that little bit of extra fat that makes it a good spot.

In any case, try some places other than your tummy -- love handles (or in your case where you'd imagine such padding might be :-)), waist above the butt, pretty much anywhere.

The best location has a minimum of disturbance in terms of stretching, bending, movement in general (tricep area is good this way too).

I am quite lean myself (5'4" and 110). I never even bothered to try my belly for sensor sites, I have to sit down and slump in order to pinch up enough for me to give myself a shot. I figured a Dexcom site on my abdomen would be a no go. I have had great success using my hip/upper buttock/love handle area.

With my last sensor change, I tried my arm, as I have read a lot of people like that area. I love everything about it except accuracy. :( In my hip area sometimes the first 24 hours are a little wonky but things are super after that, in my arm I'm getting a really jaggedy line on my receiver. I really had to work hard to pinch up a spot on my arm, I'm thinking there just isn't enough fat there.

I would definitely try using another area of your body. They are FDA approved for abdomen but can be worn anywhere you have body fat.