This is how I keep mine on for 3-4 weeks:
http://www.tudiabetes.org/group/dexcomusers/forum/topics/finally-getting-my-dexcom-g4?commentId=583967%3AComment%3A3092152&groupId=583967%3AGroup%3A168831
1. No
2. Almost all last 10 days, some a little less, most a couple days over 10. Never had a full 2 weeks on one sensor.
3. None of them are past the expiry date
4. N/A
5. Arms, exclusively. I use adhesive.
Most recent batch delivered end December:
Ref 9500-25
Lot 511 4226
Exp 2014-07-03
First two lasted 16 days, ran perfectly for 15, then loads of ??? errors. Current sensor on day 20, still running well (no recent ??? errors). On left side of stomach (love handle). Opsite flexfix tape around sensor plus (for first time) skin tac wipes.
Self funding and switched to Vibe + Dexcom in November (after 3+ years using MM system). My main motivation for switching was the longer sensor life, but even if the sensors were free and only lasted 7 days, I would still stick with the Dex G4 because of the amazing accuracy
Joel
A little frustrated - been on Dexcom4 for a little over 2 months. never been on cgm before. i was so excited to have my first sensor last 26 days! thought i was going to be able to save lots of $$$. not the case! that first one was just a teaser; haven't done anything different. wear it in the same area (my upper stomach, moving from side to side). i had one last 16 days, but the rest only 7-9 days. this last one i'm getting ??? on right now - all last night i was getting alarms that i was low. checked my BS on my meter and i was fine - in the mid-80's, low 90's. calibrated it again, ate some breakfast and it was spot on again until the dreaded ??? about an hour ago. only 9 days on this one too.
Gayle, I think your early success with 26 days has made you a bit more expectant than the average Dexcom user. The fact is the sensors are expected to last only 7 days. The fact that at worst your sensor only lasts 7 days is really quite remarkable. The reality is you got 42 days out of 2 sensors. That is 6 weeks worth of sensors. There are a few things that cause the dreaded ???. One is moisture under the sensor. This can happen after a shower or bath if the transmitter is not tightly seated in the sensor. There are a few quick fixes. One is to pop the transmitter out of the sensor, wipe it off, and pop it back in. Usually the ??? resolves pretty quickly. Another way to avoid it all together is to think of the sensor and transmitter as a ski boot and binding and always orient the toes facing upward. This makes it far less likely for water to collect underneath. My current sensor is 16 days old and is on the back of my arm. It has been consistently within 10 points of my meter and I'll replace it when it gets wonky. But I understand if I get less than 7 days - Dexcom replaces the sensor. If I get any more than 7 days, it's gravy.
"Another way to avoid it all together is to think of the sensor and transmitter as a ski boot and binding and always orient the toes facing upward. This makes it far less likely for water to collect underneath."
Thanks Clare, I have never heard of this (because for some reason Dexcom recommends it horizontally) but it totally makes sense moisture-wise.
I will have to try this out next time (I always have it on my upper stomach, but never tried it vertically).
i haven't tried it vertically yet either. your analogy makes perfect sense, so why do they recommend horizontal? so . . . my sensor went back on after about 2 hours and seems to be pretty accurate for now. i haven't had a shower in 12 hours, so it wasn't because it got wet. not sure why i would get ??? then back to normal? is it just a sign that it's ready to poop out all together? or could it last some time again? yes, my first sensor lasting 26 days sure was a dream and so i thought things were going to be better than expected. i know they're not supposed to last more than 7 days, and yeah it's the expense, but it's also the mental anguish i go through every time i have to change the sensor. it's just a mental thing i go through every time i change my cgm sensor or my pump inset :(
I'm with you on the mental anguish part. And as far as the ??? go it just means the sensors is having trouble getting a signal. This can be from some kind of interference - like water, or sand, or dog fur (yes I found that underneath one time), or a clot of blood collecting at the site. This can also be a sign that the sensor is on the decline. There are other more subtle signs including dropped readings and really off readings. My insurance company covers sensors 100% without any copay so I could go completely by the manual and change every week, but in my experience the sensor readings are generally much better in the second and third weeks, and once you're in the groove you just don't want to stop. Dexcom only recommends horizontal because it only recommends abdomen and the way the body moves I guess putting it horizontal is more comfortable. But since I don't use my abdomen and prefer my thighs and arms vertical is more practical.
There is a post on Facebook which I would love to share by Steven Ponder, MD it is entitled "Early and Late Signs of Sensor Decay".
"Anyone using a CGM device beyond it's rated use limit (up to 7 days for this device shown, the Dexcom G4), uses it at their own risk. Having said that up front, it's important to know when a sensor is starting to degrade.
Sensor degradation happens at different rates based on a lot of variables, including placement, how much movement the site endures, temperature extremes, and even the unique qualities of an individual sensor unit itself. The point here is to know when to start seeing changes in the trend pattern that might tip you off to an upcoming need for a new sensor insertion.
The wobble I show on the right is an early sign, as is the "rougher" appearance of the longer time frame display (24 hours) on the left. In other words...less smooth. Now wobble can occur anytime, as well as skipped data points. They typically self correct. But as these events accumulate and you KNOW that the sensor has been in place beyond it's rated lifespan, then be prepared to change out the site.
If this happens BEFORE the end of the first sensor session, you might want to call the sensor company to let them know. Often it will be replaced. That's no small amount of money as most of us know. Share this tip freely and add your own comments and experiences for all to share."
I'm not sure if the photos will show up but I will attempt.
I definitely see the wobbles at night, but I always attributed that to the fact that I move around a lot while sleeping (so I'm putting pressure on the G4 at times).
I did however get the random 1 red dot (like the top-left image above the 6pm) happening with my last sensor... that was the first time I had ever seen that (I've been on the G4 for 14 months).
Has anyone ever tried vertically on their abdomen?
Yes Elizabeth the toes up reference is to the narrower part of the sensor facing upwards. I just opened a brand new batch of sensors and the one I have on now is 17 days old and very accurate. I don't know if there is any veracity to Dexcom maybe tweaking them somehow, especially given that Gayle got 26 days from her first sensor, and 16 from her second. But anything is possible. I'll be anxious to see your results from the expired sensors.
I just changed my last sensor after 25 days (a record since starting in November). It had an unexplained indident around day 11 where it gave ??? for around an hour before recovering (I have no idea why). It then ran very accurately until the last 24 hours or so where it read fairly consistently lower than a fingerstick, gave a wobbly trace and had several ??? episodes. I only kept it in our of curiosisty to see how long it would keep going.
As an ex-MM CGM user one of the (few) advantages of the MM system was that it would report the isig (which is the raw signal output (in nano-amps) of the sensor allowing you to estimate the how well the sensor was performing particularly at the end of its life. The Dexcom is pretty much a closed system.
Joel
(Reposting after deletion) Clare, I know the sensors are only SUPPOSED to last 7 days, but some of us pay tens of dollars for each sensor, and since we were able to get more time out of older sensors it’s upsetting to be paying twice as much now. Seeing a change in the more recent sensors has been so disappointing, it makes me so tempted to go back to the 7+ where I’d routinely get 2 weeks. I’ve been keeping these in even after they start dropping a lot of readings, just in an attempt to save money. I get one or two readings every couple of hours which are still spot on, and just supplement with blood testing. Not ideal obviously, but it’s the only way I can afford the sensors.
As a sidenote, someone was kind enough to send me a set of his sensors to try…They’re expired, but hopefully will still work and allow me to compare to figure out if it’s just my body causing the issues or if something about the sensors has actually changed. This should be a good test, I’ll post the results here!
Glad you got the sensors to test your theory. Mine is still going strong after 18 days.
That's nice info Adrien. I didn't know the make up of the sensor, but now that I do I have more desire to get life out of them.
I'd like to know what people use as a sign that they need to change the sensor. I just got new sensors in January, and decided to go as long as I could stand having one on me. I went almost 10 weeks (Yes, 70 days!) before I decided to change due to 1. The accuracy was getting a little too much off for my tastes, about 30% to 40% off on a median of averages. The average accuracy dropped to over 10% off after about 8 weeks. I also saw the "wobble" as described above very often. And 2. The sensor was starting to hurt. A low hurt of about 1 on a scale of 1 to 10, but it was noticeable. I believe I was beginning to get a bit of an infection around the insert site. The old site hurt a little for a couple days after removing it too. Never got red though. And before changing I only rarely got the ??? reading, which wouldn't last more than a few periods (a period being the 5 minute interval for readings.)
What's your normal reason for changing? Accuracy? "???" in the display? Just tired of it's location and want to move it? Full moon?
My normal reason for changing is accuracy or more precisely a drop off in accuracy or ??? or the hour glass. Eventually I get one or more of the 3 and finally change it out.
With the 7+ it was a loss of accuracy, including some wild spikes or dips (like 1 or 2 readings in the 300's when my bg was actually under 120.) With the G4 it's always loss of readings, I'll get ??? or the hourglass for an hour or two in a row, followed by one or two extremely accurate readings and then back to ???. (Which is another reason this is so frustrating, it shows the sensor still CAN read accurately, but for some reason acts like it can't.)
Seems like the newer (2014) sensors are a smoother lighter plastic (the throwaway part that places the sensor in seems a little flimsy), and the transmitter has a little more play in the housing than the older ones I have.