Problems w/Seven Plus: ? readings, sensor failures and sensor errors

I started using the Seven Plus a week and a half ago. I had four sensor errors with the first sensor and am now on the second sensor. I have had one sensor failure with the second and have had a couple instances where I get the ??? in the status box for extended periods of time. It has now been almost three hours with no readings from my Dexcom. Has anyone else experienced problems like mine? My current sensor is placed on my side below the ribs.

I am also noticing that my Dexcom readings are often more than 30% off of my meter readings. Any suggestions would be greatly appreciated since I am losing any confidence I had in this meter. I bought it to help me with LBS while mountain biking and while sleeping at night.


Maybe you got a bad batch of sensors? I am assuming since you just started the system that these sensors came out of the same box? Definitely call DexCom about this, they are pretty good about replacing sensors. You should not be getting so many ??? readings at all.

How much meat/fat do you have in the area where you put the sensor? Did you pinch the flesh up when you inserted it (helps the wire set properly in your flesh)? I had problems with sensors if I put them too close to my ribs where I have less flesh. It almost sounds like you have a transmitter issue since this keeps happening. Call tech support ASAP to be sure. Once you get the darn thing communicating, you can work on the readings issue. The Dex is almost scary accurate once everything is working right. I find that if I calibrate when my BGs are dropping or rising alot that the Dex get off alot. If it is off and I do a finger stick, I will put that number in 2 to 3 times and the system seems to resync and be more accurate than it was before. Punch in your BGs often, this will help it get more tuned in to you as well. I find that the sensor is better after the first day and does pretty good until the sensor dies on me.

There is a learning curve to using this and after almost 3 months, I have gotten the hang of it. It isn’t always right but it is good about letting me know about lows or if I am dropping fast. I don’t care so much if the thing says I am 120 and I am really 90 if it tells me I am dropping like a stone I can fingerstick and avoid a low. I totally understand your frustration, hang in there, it does get better.

Wow! This is bad. I hope someone can help you. I’ve only had this cgm for a little more than a month and am on my 3rd sensor. I’ve had none of your problems. I did have a problem with the battery icon continuing to scroll constantly most of the time so that I couldn’t tell whether or not the receiver was charged. The company said they’d had a few other people with this problem and they replaced the receiver by overnight mail. Be sure you’re talking to the people at Dexcom.


There’s a great chapter (which I originally skipped) in the book that tells you how often the sensors should fail. My expectations when I went on the Dex were that it would work great 24/7. However, the chapter in the book details how often failures will occur. I think my first sensor had three errors for a total of about 4 hours. When I looked it up, this wasn’t outside the expected range.

I’ve since come to believe that the smoother the set-up goes, the smoother the sensor will go.

RE: accuracy. They say (and I believe) it’s all about training the sensor. It’s not uncommon for me to do 4-5 tests in the first 5 hours and that improves accuracy a lot, unless I’ve put the sensor in a bad place (less fat). I tried that once and never got the sensor to perform well.

Have patience w/ it. It’s not nearly as perfect as I’ve found the pump to be, but with a good sensor running, you’ll get awesome performance most (but not all) of the time. :slight_smile:

I got a shipment about 2 weeks ago (I can’t remember the exact date). The weather was running around 98 degrees in my area (MidWest) and I ran to the FedEx truck when it arrived in front of my house as I didn’t want it sitting outside. So far I’ve had 3 “Failed Sensor” and 1 sensor gave readings that were 100 points off from glucometer and it gave ??? for 6 hours. Dexcom replaced all of them and I tried to call FedEx to find out if the buildings that shipments go through are stinking hot when it is stinking hot outside in the area - the FedEx guy on a phone said he could give me the address to the building location but he said he didn’t have a phone number (which doesn’t help me to slow mail find out the answer to my question). The sensor packages show that it should not be in temps above 77 degrees which makes me wonder if the extreme heat during shipment caused this current box of sensors to act up. The current sensor I have on isn’t doing as well either - I haven’t gone swimming with the sensors and when I was taking a shower I tried to keep the site from getting wet, I also calibrate numerous times. The three sensors that are being replaced were only worn for 1 day to 3 days at most each.

Just of curiosity, did you get your bad batch of sensors recently? I’m receiving 3 replacement sensors this week and hoping that I won’t have another headache of bad sensors (and hoping weather outside isn’t so extreme in the areas that my shipment travels). Even though I just got the Dexcom the beginning of May, I’ve become dependent on it to alert me when I’m dropping in the night (I don’t feel my lows or have any symptoms even when I’m at a level of 32 and I have night sweats from lows - Hubby can’t even spot my lows anymore like he did many years ago… the sun wreaks havoc on my blood sugar levels too, I’ll drop just from sitting out in the sun watching my kids play in the kiddie pool).

Good Luck to you!

My niece is on Day 8 (we restarted Dex today, what a dream come true after MM’s restarts) of her very first Dexcom sensor. Rep inserted it, along with her Mom, so this one is a good one. Yes, we have had ??? almost every night around 3am thru 5am. She is having a growth spurt, BGs are rising extremely rapidly, necessitating double her basal. After three hours of this, Dex kind of throws in the towel. We left Dex alone and when her BGs stabilized around 5 or 6am, we got the readings and then calibrated. During times of steep rises and steep drops, it can be off 30 percent, at least for us. This was true with the Minimed sensor as well, only we had so much trouble calibrating. BG really needs to be stable calibrating for MM sensors. With Dex, it seems it needs to be semi-stable. We can calibrate at a higher BS level. I’m sure others will chip in and tell you how to get Dex to read very accurately, as you will need it for mountain biking. I don’t expect the cgms to be extremely accurate, just reasonably so. After dinner when she is spiking, I can still get the trend arrows and that helps immensely. Overnight, I have been getting the ???. Will be even more aggressive with the basal overnight tonight, keep checking, and hope we don’t lose Dex readings. I appreciate the pain-free insertions, and the readings have been more accurate than the Minimeds so far. I really love how we don’t have to take the sensor off every three days, put it on the receiver, and put it back on to restart. Dex sensor stays on the body for seven whole days, and you leave it on the body when you restart. It seems to get even more accurate as time wears on. At some point, it will lose readings, but readings have been great after restart so far.

Thanks for the comments everyone. I also found out yesterday that my alarm was no longer working. It will vibrate, but it won’t beep. I spoke to Dexcom CS twice yesterday and they are replacing two of my sensors as well as sending me a new receiver. Their customer service is very good. I hope to have better luck moving forward.

Yes, that is good customer service. Sounds like you have numerous problems so might as well start with a whole new package. Dexcom is awesome. Nice to know that they will replace the sensors.

Glad to hear you are getting a new receiver, I really wondered if that was the problem…

I am on my 4th sensor and my second week with Dex. First week went great with first sensor and I changed it after 7 days. When I replaced it, 2nd sensor worked all day and failed in middle of night 2 am after several false low readings. Replaced sensor in morning from same box, worked all day fine and again, 2am, low reading then later failed. Now on the forth sensor from box and day 7 and working fine. I called Dex and told them, they have already sent me two replacements and prepaid packages to mail in the failed sensors. I asked if it could be a bad batch of sensors and they told me possibly but keep using them from box. I also got a call from Tech Support wanting me to submit data for quality control. I was completely impressed with customer service.

Dexcom has changed everything and I love it…

I started the Seven Plus system late in June, and have had lots of sensor failures, bad readings, and ??? signals since then (only 1 sensor failure in about 5 months on the Seven system). About 5 failures in 5 weeks. Dexcom is very good about sending replacement sensors, which also fail at about a 50% rate. Dexcom says this is a “known issue” and their QA people are working on it “around the clock.” They also insist it’s a sensor problem, not a problem with the Seven Plus - it’s “coincidence” that my problems started when the Seven Plus started. We’ll see. If you have a failed sensor, call Dexcom and they’ll cheerfully replace it. The Seven system was so good, and their customer service is so good, that one hesitates to alert the FDA about the problem. I hope they’ll take care of the problem soon.

I got my 7+ in the middle of June and the 7 sensors that I used so far lasted 7 days (they might have lasted longer, but I pulled them according to the instructions).

THANK YOU///8-15-09

Odessa, I love my 7+. Unfortunately that does not mean that you will not be disappointed with the 7+. I am reading the forums a lot and your mileage might vary. The MM CGM gets the worst rep. I never considered it. It is harder to chose between the Nav and the 7+. There is no universal truth because the sensors depend on a chemical reaction that differs from person to person. I don’t see any downside in going for your own experience. If you hate the 7+ you can still try the Nav. Just don’t give up on CGMs. For me the switch from bg strips to CGM is comparable to the switch from urine strips to bg strips. If you ever had to control your bg with urine strips you can tell how impressed I am with my 7+.

As for the OmniPod: I am wearing the demo pod right now. I have decided to go for the real thing.


Great. Good luck.

I just started wearing the Seven Plus a week ago, after wearing the Seven for over a year, and can’t believe how much more accurate and consistent it has been. I rarely get a ??? which I frequently got on the Seven, and I just fooled it today after soaring through the first seven days. A big difference I saw in the two was that the instruction booklet has gotten much more specific as to which way to wear it (I used to sometimes wear it up and down, but this time the book says specifically not to do that), and it tells you exactly what to do with certain error reports or blood drop symbols.

I know you posted this last month, so hopefully things have gotten better for you. I would also say to check your book for specific suggestions on how to deal with issues. It really can be a great tool.

Thanks Toni. My Seven Plus is scheduled to be delivered on Monday. This will be my first CGM so I"m counting on you all to help me get adjusted to it.

My last box of sensors has been a total dud. I am wondering if they have a quality control issue at the moment - up until now, my Seven+ has been pretty accurate, once it gets dialed in, after the first day or so, But last night it gave me a 43 when I was at 96, and after breakfast today (a bad breakfast, had some kind of hidden carbs in it) it gave me a 300+ when I was at 192.

I just had another failed sensor. So, of the first four sensors I got with my new Dexcom, I had problems with 3 of them. Of the four replacements they sent me, I had problems with another one of them. I think they definitely have a quality control issue.