I got the Dexcom G4 about 2-1/2 months ago, and while I like it and have had SOME very accurate experiences with it’s been a little disappointing in the way of accuracy. I’ve called Dexcom several times, and they’re always extremely helpful and offer to replace the faulty sensors, but I just want them to work. Dexcom gave me the guidelines of only to calibrate it when it asks you to do so OR when it’s off by more than 20% on readings above 80, and off by more than 20 points on readings below 80, so I follow that to the letter, but it’s often still off by 50+ points. I always use the same meter for testing, I always put ot on the abdomen as they recommend, and I only clean the insertion area with alcohol as they recemmend so I don’t know why it’s so inaccurate. Do any of you have these issues? I look forward to the Gen 6 where no calibration and fingersticks will be needed!
Sorry to hear you are feeling so frustrated! I have had my G4 for about 3 1/2 months and I have had the opposite experience in that more often than not, my results are spot on! I don’t typically use my abdomen, as I have found that my comfort level and results were the worst there. I use the top of my thigh and get awesome results. I have bled with the last two sensors I’ve inserted and I’ve found that I have a rockier start in that situation. Both times, I’ve actually stopped and restarted my sensor after several hours and that seems to help with the numbers not bouncing around so much. I think sometimes the sensor needs to ‘marinate’ longer to help with accuracy. I’m on day 4 of my current sensor and every time I’ve tested in the past two days, the numbers have been exactly the same or within one or two points of my dexcom. I’m not sure why some folks are having such good results and others are struggling…it’s such an individual thing, you know? Anyway, I would try another spot for your insertion, and not worry so much about the numbers you are getting during the first day or two. And try shutting the sensor off and starting it up again with a new calibration window and see if that helps. Sorry if you’ve tried all this already and I’m just running my mouth 
good luck! I hope you can get some better results!
Are you still having this issue? I just started researching this. I'm having the same problem.
Yes, I still have this issue. It's right a lot, but off more than it's supposed to be usually at least 1-2+ times per day too. Like everything, the technology will get better with time, so I'll be one of the first to upgrade to G5 and G6 as they become available.
Denise,
Sorry you are having difficulty with the G4. I find it works best to calibrate before I go to bed and when I wake up in the morning. In other words, when my blood sugar is not rising or falling due to a recent bolus or food, when the arrow on the G4 is level and not up or down. Good luck, hope you can get good results.
Yeah--that's what I always do, but it doesn't seem to make a difference.
Have you tried sites other than abdomen? And vertical rather than horizontal? I find my best accuracy and longevity with vertical on back of arms and FS done on hand of side it is located on. Also calibrate when arrow is flat. I will get a V curve if I rollover and sleep on it but it will rebound back when I roll off and the juices get moving again.
If I've laid a carb bomb I do not expect it to be able to keep up with the rise, but once it plateaus and holds for a while it will usually be within the 20/20 rule. Remember the higher the BG the larger the allowable spread. For me trends are as important as the "number". If I find myself hanging high longer than expected after a heavy fatty meal I will double check before correcting but usually if I'm past the first 2 days of a new sensor or a reboot it will be close enough.
I have issues when the adhesive/tape begins to peal and the site is not locked down well, especially if I've banged it a time or two. Have been using opsite/flexfix over the tape with good results. Use an old sensor bed as a template to cut a hole in a piece that covers the tape on all sides. As it begins to peal over time I trim and reapply. Can usually do this by my self with aid of mirror, but need an assist at this point since I'm casted for an on the ice slip and fall. I can always tell when it get loose by the increase in the BG difference between sensor reading and FS.
I moved from abdomen since it flexes so much and was giving me erratic results. Thighs were accurate but I could not keep the sensor on what with tight pants/skinny jeans etc.
Don't know if you have tried any of this, but it works for me!
I have a replacement G4 sensor & receiver (for out of warranty one) that is in its first week. I am hoping that is the reason for mine's inaccuracy. The one that died was much more accurate. I keep mine in for 2 weeks so am hoping the second week improves. I hope!
I've tried most of that except I refuse to wear it on my arm where it's an eyesore and invites questions from everyone. But the rest, I've tried. I tink while the G4 is the best there currently is, there's just a lot of room for improvement.
Do you orient the sensor wire pointing down or up? Or does it even matter?
I use upper back of arm so it and the opsite patch I use is covered by my short sleeve shirts, most of my coworkers don't even know it is there, unless we are talking about it. Never been a sleeveless shirt wearer - so for me not a problem.
Have you tried high on arm on the under side? Near armpit? Might work and be less obvious if you're in a crop top. Also have friend who uses vertical on the shoulder holster/ side of chest/ under bra side panel area so very under clothing/cover.
I let gravity pull the inserter off during one handed insertion so that would be small side of transmitter down, wide side and snap clips up.
I'm sorry you're still having issues Denise. I am in the "my dexcom is usually within the statistical limits of blood glucose meters +/- or 20% on readings over 80" camp . As a general rule the meter and dexcom match fairly well. The only time the Dex is off by more than 50 points is when it is moving rapidly and I don't expect it to be that accurate when my blood sugar is not stable. I use the Dex for trends, not for absolutes.
Lately mine's been inaccurate outside of those parameters about 25% of the time. But then when it's on, "it's right on" if you know what I mean. Mine is almost always off right after breakfast. It will read 70 or so, but I'm really at least 130-200. It happens almost every morning. Maybe it would eventually catch up, but I feel like since the insulins are so slow, I don't really have time to wait and see to correct, I'd rather correct as soon as I know it's flying upward to blunt the spike. I guess when I see that it's trending up a bit in the mornings is how I know to check it and correct based on my meter result.
It does eventually catch up - usually about 15-20 minutes later. If you routinely shoot up after breakfast is there maybe something not quite right in your I:C ratio for breakfast ? Or maybe you need to make different choices for breakfast - like eggs and bacon instead of something more carby. I do find though that the Dex readings never get as high as I am and never get as low as I am and Dex takes a very long time to recover from a low or a high. But I realize there are limitations to every D device I use. For me the Dexcom has far fewer limitations and allows me the freedom to sleep and exercise safely.
Oh it's complicated...I can eat the exact same thing every day, and some days I will go high, some days I will go low, and some days, I will stay perfect. I just don't think anything is ever the same with this stuff. I think I'd be in great shape if the insulins were faster and the cgms more accurate.
Girl, I am right there with you!
I have been using the Dexcom G4 for about six months and I have had a total of four sensors that completely did not work. Three of them kept insisting that I was in the forties and diving when I was around 100 (and stable) and the other one just seemed to measure whatever it felt like. That made for some rough nights when you're trying to sleep and it won't stop beeping no matter how many times you tell it you're not dying.
To their credit, Dexcom technical support was very polite and responsive each time. The weird thing is that I've had some sensors that were almost 100% spot on with my blood sugar, and from a similar application site (pump is usually in my abdomen so I use upper thigh). I've recalibrated, double-checked my meter... one day I counted and I'd pricked my finger almost 20 times in one day because the readings always seemed so far off before I just chucked the stupid sensor in the garbage and put in another one - NOT an improvement in my quality of life. And I feel like for what these cost, we should have a reasonable expectation of accuracy.