I have been using my dexcom CGMS for about 2 months now and recently my readings are way off! It begins fine, with readings that are just above, right on, or just below my monitors. But within a day or so, it starts to give me alerts for readings that are not even close to what my monitor (and my body) feels. The worst is when it keeps me up with alarms all night long by tell me that I am "LOW" when I am in the mid-100s. Has anyone else experienced this? Is it a sensor problem? I will be calling tomorrow (due to memorial day) but I wanted to see if this is a problem that occurs quite a bit. I love my CGMS when it was working and just want to get back to that point.
I am having the same issues-- only on my second sensor. Wildly inaccurate. Saying I'm low, below 40 when I'm actually over 100. Saying I'm high, over 200 when I'm actually at 90. Jumping all over the place... keeping me up all night with erroneous alarms... Dexcom so far has been quite a disappointment for me. I really had high expectations, and my experience so far wouldn't have met even the lowest expectations. I'm happy for the people it works well for, but it's just not looking like I'll be one of them.
Sometimes Dexcom is reasonably close to the finger prick reading. However, several times a week Dexcom is over 100 points from the BG meter. Sometimes higher. Sometimes lower. Not only is this frustrating, it is very dangerous since I could be getting very low and not know it. Also, often when I enter a true BG reading into Dexcom so that it gets to where it should be, there is an ERR1 message. I wait the 1 hour and enter a new reading. Sometimes the ERR1 still comes up. I wait another 15-30 minutes and try again. If still ERR1, I put in a new sensor. That often ends up occurring in the evening so by the time the two-hour startup period ends, it is 1-2 hours past when I usually go to bed. During the 8 weeks or so I have used Dexcom, I had only two periods where a sensor was usable for seven days. I have been on the phone many times with Dexcom and they cannot tell me why the 100+ point discrepancies and/or the ERR1 messages.
dexuser -- That's certainly real disappointing. Sorry it's not working out for you. I've been with my Dex Seven+ since October of last year, so still a relative noob, and I am having the more common experience than yourself, it appears, where I get 10-20 days out of a sensor if I want (I often go ahead and change the sensor weekly just so I don't build up too much supply of them). I put them on my upper arm these days, and have only whacked one off on a doorway (Ugh!).
Additionally, most of my readings from my CGM are just fine for me. Most of the time my manual BGs are spot on with the CGM if I am trending flat. I do note differences when I am trending up and/or down, but this is to be expected with the 10-20 minute lag the Dex has vs. finger pricks. I know several folks here say to always (ALWAYS) manually test your BGs before making any sort of moves one way or the other (food and/or insulin), but I have found my Dex works as good as my One Touch Ultra for tracking my ups and downs, so I just roll with it. I have no issue injecting based on the readout from my CGM. But, I'm also the guy that uses one needle for my insulin injections until the numbers rub off (about 24 days or so, generally), so take that into accounting. YMMV.
Good luck sorting things out with Dexcom. I hope you can get it to work out for you. I found the Dex to offer me the single biggest change in my diabetes care in 30+ years. As a direct result of my Dex, my A1c is now at 5 (May 12). I've never ever been anywhere close to that -- my last couple of A1cs were 6.7 (Jan 12) and 6.5 (Sep 11).