What is your "grace period" for a new sensor?

I'm relatively new at this, still I've had great luck with the G4 so far. I put in my new sensor on Sunday night. So far there have been a few periods of 20/25 point differences. As opposed to other sensors, which have been spot on starting on day 1 this one feels like it's always a little behind. It's not "failing" per say, but not up to the usual performance I've seen.

Maybe I'm just being too demanding, what would you do? Or more apt, when do you feel a sensor just isn't going to work?

What does "spot on" mean? You mean when the Dex matches whatever meter you own? I have taken blood from different fingers within moments of each other (specifically when the Dex asks for two BS when you are first calibrating a sensor) and had them be as much as 20 or 30 points apart. My point is, none of these devices is perfect -- not the Dex nor the One-Touch or whatever meter you use. A "20/25 point difference" doesn't seem remarkable to me at all when assuming that none of these things is perfectly grabbing your blood sugar levels.


Where did you put this one ? Is it in a completely different spot than any of the others ? Those would be my first questions. According to the literature it only has to be within 15% of your blood glucose meter to be considered accurate whether it is high or low. So that can be a wide margin if you are at 200 mg/dl. on your glucometer, anywhere from 170 - 230 on the Dexcom would be considered accurate. I find it is a bit less accurate at the lower end of the spectrum.
I am likely to think a sensor is not going to work when I get the ??? or the hour glass indication more than once. Or it drops readings. I think you have been very lucky - or maybe spoiled by having spot on performance from day 1, most people find day 1 with any sensor pretty much sucks wind and it settles in after that. If it doesn't settle in by day 3 then I would get on the phone with Dexcom. They have been very responsive.

It's on my stomach as usual (same position, different side). I think I have just been spoiled by 2 really responsive sensors so far. I mean, the last 2 I worse were almost always within 3 to 4 points of any stick test. The one I have on now seems to be more towards the 15 to 20 point end of the spectrum. Maybe it will settle down. Still instead of a nice solid line like I usually get, I have a lot of jags on this one, where I've had to calibrate and it's been off by 20 points. Example. I ate, bolused earlier and the dex read 180. I felt higher than that, checked and my Freestyle had me at 204.

No dropped readings or ??? so I will stop being picky and keep on :D

Exactly this. If a meter calibration number matches the Dexcom exactly that's just a coincidence and in no way means that they're both perfect at that point. I don't think I've ever had two startup meter numbers the same with a one touch and that's from basically the same drop of blood.

OK so I re-read the marketing material I got about accuracy and the Dexcom G4. They count as "accurate" the % of readings within 20% of reference YSI when >80 mg/dl or within 20 mg/dl when < 80 mg/dl. So like I said, it seems to be less accurate the lower you go. YSI is the reference standard used to measure blood glucose.