I've on day 4 of my first Gen 4 sensor. After the first day it's been very reliable. Yesterday I had an hour of the "Wait" hourglass followed by ???. After that the sensor kicked back in and seemed to work great. Mid-morning today I got a sensor failure alert.
Although I had some 7+ sensors replaced when they weren't working well, I think I only had 1 sensor failure in 1-1/2 years. So it's a bummer to start my Gen4 career this way. But I've got a new sensor inserted and will hope that the first one was a fluke.
I, too, have had mixed results with the G4 but the good results have far outweighed the bad. My first sensor had excellent correlation with my fingerstick readings, had almost no data dropouts, and lasted 16 days. My second sensor had several ??? periods but performed well enough to last 10 days. I'm on day 15 of my third sensor and it's still going strong. This sensor, however, will incorrectly dive into the hypo range if I pressure it against my mattress when sleeping. Other than that it has performed very well.
Good luck with that second sensor. I think that where the sensor is placed has a lot to do with its performance. Unfortunately, we can never know exactly where to place a sensor. In the end it's left to chance but I think the odds for good performance are in our favor. I'm considering putting my next sensor on my upper arm, something I've never done before. Please update with your second sensor results.
I have not had the dreaded "sensor failure" message. I have had the ??? and one wait hourglass, but that was all with my second sensor which they have replaced. The one I have on now has been in place only since Tuesday afternoon on my thigh, but it has been really close to my fingersticks. I agree that sensor placement certainly can impact performance and am far too new at this to really weigh in on the perfect spot. Obviously being a "newbie" I placed the first sensor exactly where they told me to, horizontally on my abdomen it lasted the longest of any of the sensors so far and gave very accurate results. The next 2 were vertically on my arm and both gave me uniformly accurate results, but did not last as long as the first one. We'll see how long the latest sensor is reliable but I have to say it is the most comfortable of all I have worn so far.
I'm hoping that I have a "fluke" G4 sensor also.. I'm on day 3 of my first G4 sensor and I am also still wearing my last Dexcom Seven+ sensor and comparing results between the two and finger sticks. so far my old Seven+ is giving more accurate readings than the new G4, and the Seven+ is definitely detecting rising numbers more quickly than the G4. also, the first G4 sensor I inserted caused immediate profuse bleeding and had to be discarded. this only happened one time ever with a Seven+ sensor. I am defintely hoping all these issues are just flukes.. I was (and still am) hoping the G4 system is going to be even more accurate than the old Seven+.
I got the hourglass and the ???'s. Once I got antsy on teh ??? and pulled it because I had already restarted it (shhhhh), but then I got it twice on relatively new sensors. First time it came back in an hour or two. I was out and about so I just left it alone and it started up again. Then again on a different sensor. Took three hours but finally started. I talked to someone in tech, and they said that it happens but is not an issue if it starts up again as it usually does. Didn't like that but it was true. I'm going to do a post on this, it appears to do with static charges.
My first sensor did that after less then a day, so I feel your pain. 2nd one lasted 7, third lasted over 2 weeks and I am on day 3 of the new sensor. Showering and exercise seem to be the cause of the dreaded hourglass and ??? I now cover the sensor while showering and wear something over it during exercise.
I fold a paper towel into a rectangle, and use water proof medical tape to "seal it" while I'm in the shower. As long as I keep the shower short enough (usually around the 6 or 7 minute mark) it never gets wet enough, or steamed enough to be a problem. I started doing this after day 3 on my CGM (when I also lost one due to ??? after a shower) and I have not lost another since. Yes it takes a moment of prep, but it's worth it!
I also got hourglass and ??? after showering. Never had this problem in over 3 years with the 7+.
This is all great info! I just received my G4 on Thursday, charged it overnight and was contemplating doing both the new and old sensors at the same time to see the differences. I'll put the new one in after I shower tomorrow morning, either way. As far as sensor placement, I really don't see how people are finding all these areas to use! If I put it on my hip, it hurts when I inevitably roll on it when I'm sleeping. I can't imagine on my thigh either-same problem. My abdomen has far less real estate to use, with the pump and CGM fighting for space, and too much scar tissue from 41+ yrs of T1, plus a few surgeries.
There is another thread here about sensor placement. For me so far the best location has been on my non dominant arm. I have gotten the longest sensor life there and the best readings. 2nd best is upper thigh so far but I got my Dexcom in November so it is a small sampling size.
I've been using CGMS for 5 years (MM for 3, Dex for 2). The first year I used just my stomach. But since then have primarily used my arms (Dex) and thighs (MM and Dex).
Best readings have come from my arms, although thighs are comparable to stomach.
To help with 'real estate' and give my stomach a break, I use my lower back/hip area for my pump sites, after 10+ years of using stomach only. (Currently rarely use my stomach, except injections by syringe !)
I started my first G4 last week (inner thigh), while also keeping my Seven+ in (arm). Both have been on/off somewhat, but I'm now on day 8 with G4 and it's pretty close.
At times, one would be 80ish, and the other 120ish, and meter BG would be 100ish.
In general, G4 was usually lower than the meter BG, and slower to show an upward trend after eating.