Dexcom Sensor failure - 8 total

My husband had 8 sensor failures within 3 days and dexcom support said it was the sensors. Since he is subject to radical sugar lows we became paranoid and convinced the tech support to send a new receiver with replacement sensors. We are awaiting the new receiver but we are concerned - he started using the Dexcom in August 2009 and yes we had sensor failures but not in a row. Has anyone else faced such problems? The Dexcom is great; but after you become dependent on it and it stops working and then they say it is sensors - well.

This site is very encouraging my husband has seen he is not the only one and doesn’t feel like he is fighting a loosing battle.

Thank all of you for your inputs.

You’re talking about “Error 1” and/or “Failed Sensor” messages, right? (Not just staying stuck in “???”)

Dexcom USED TO make a special effort, when preparing a shipment, to make sure that the Sensors within the 4-pack came from different manufacturing lot numbers. But they don’t do that anymore, so it is possible that you got an entire pack of bad ones. (And yes, even a double order can contain all 8 from the same pack.)

But I don’t think that “bad sensors” from the factory is the most likely problem: Rather, if you live in a cold part of the country, they might have been out on the doorstep for too long. Freezing absolutely kills them, every time. Did you upload the monitor’s data so that they could see the “raw” voltage figures which the receiver was getting within all of those new Sensor attempts?

How do you get the Raw voltage figures from the Dexcom? I have downloaded the data from the receiver but this stills seems to be the values displayed by the Dexcom itself or am I wrong? I would like to see the raw data so that I can understand how the dexcom adjusts its calibration. We had one sensor that became far to sensitive, i.e. it understood that the blood sugars were moving but thought they were moving far faster than they actually were. We stopped the sensor and restarted it and it worked fine.

Do you know how many of the last meter enteries are used in the calibration?


I have had sensor failures too, but not nearly as many as your husband. If I have failures (Error 1), it is usually on day seven. I have greatly and rapidly changing glucose levels, so I challenge Dexcom and get ???s fairly often. The last session went better than the previous two or three, so I am cautiously optimistic.


My husband’s BG changes rapidly too - however; we were sent another receiver and at this point we are doing great…We love the Dexcom. With this new receiver he has not had to calibrate is as much; it seems to be alot more accurate. The “???” marks are a pain but we haven’t encountered them much with this receiver. Good luck with yours - I’m sure you’ll do just fine.


It’s not normally shown. I got it directly from support, in response to my request during a short term discussion of a “???” problem. (I offered to comment on the behavior, as a professional programmer- they’d possibly found previous comments along the lines of “this isn’t good programming; you SHOULD do this in an upgrade…” to be valuable.) It’s proprietary to them, so I won’t splatter my graphs across the Internet without approval. But the graphs which support can generate for themselves, after you upload the data, do show this.

I can say that you were smart to “clear off” a bad and recent calibration entry or two which had gotten into the list for that Sensor. ALL of the entries for the same Sensor are being used, but the old ones are given less “leverage” by giving more weight to the newer ones. That’s the big software change which makes calibration of the new “plus” work better, causing fewer erroneous “???” periods which can’t be fixed, and providing better accuracy. (I TOLD them to do that in a microcode update after seeing the data. Probably, they’d probably already figured figured out the idea before I advised them to do it-- but maybe my independent suggestion of the same idea played a role in moving it along.)

As far as I can tell, ALL of the entries are used since the last “restart”, and a tiny bit of your own “personal history” gets used too. But older entries are given less “weight”. The original Seven used them all equally, leading to a very bad curve (and less accuracy, more “???” displays) as the Sensor became older and the voltages fell off.

Since it worked a lot more smoothly right after after restart, I think that Rita has the right suggestion: give it an extra 6-12 hours of “warm-up” before inserting the Transmitter and starting the 2-hour countdown. The extra warm-up time avoids a lot of the first day craziness. Every calibration which is entered during “craziness” distorts the curve, and this prevents the need to enter anything. You’re still running on the old one.)

I also do this for nearly every new Sensor, shooting them in the night before and starting the warm-up around 9 AM on the following day. (That timing keeps dawn effect and morning bG craziness out of the calibration period, it’s all over by the end of the two-hour warmup.) works great!

When you say you shoot in a new sensor at night before start the sensor, do you leave the transmitter out too while it “warms up?” OR do you leave the transmitter in the old sensor (which is still getting readings), then transfer it to the site that has been “warming up” then start it?

If so, is it safe to leave the transmitter out of the sensor? I’ve seen that flap that bends (which has the serial code behind it) and I wonder if it could get caught and jiggle the sensor. What has your experience been?


Hi Roxy:

The Transmitter stays in the current Sensor. The “flapping” electrical contacts assembly does need protection; I use ‘Flexifix’ to tape down a plastic lid from a long-ago-used-up skin cream container. (“Udder Cream”, which I use on scars. Remove the liner, use only the plastic.)

You’re looking for something with about the same width as the lids on our 50-pack glucose tablet bottles. That’s the right size to surround the whole Sensor. But you’ll want to use a lid which is just a tiny bit TALLER than that.

Per above, I recommend one with Holstein cowskin splotches on the top-- but after using it and washing it many times, you’ll find that the cow paint begins to wear off. :wink:

I have had a round of inital errors I thought were sensor problems - replace and unit seems to work.

Recently; I discovered the receiver was temperature sensitive at normal room temp 73 degrees and when I chilled down;
I restarted on a sensor I thought was bad and low and behold things starting working correctly. This has gone on for weeks.
I replaced sensor last night and readings were bad last night on a replacement receiver unit.

In frustration this am - swapped in previous receiver chilled down and immediately started working on what was a new sensor giving bad readings… It has been working all am and tracking handhelds properly within +/- 10 units or less.