I’ve had the Dex for a couple days now, but I’m finding more than a 20% difference between the sensor readings and my blood sugar readings. Does anyone have this problem? I called my trainer about it, and she suggested calibrating more often than is suggested by the receiver. It’s really frustrating me to the point of not wanting it, even though it’s en route to me now.
I’ve found that when I first insert the sensor, its accuracy is pretty craptacular for the first 24 hours. It doesnt even track changes very well and watching the numbers flail all over the place is comedy gold compared to what’s happening with my fingersticks. Calibrating more often, at that point, does nothing to help the situation.
I haven’t had a sensor yet that didn’t do that, but they have all settled in after that initial period. I think a day of watching the Dexcom bug out is worth the ensuing 6 to 13, or more, days of stable readings. Beyond that, calibrating when my BG is stable is definitely a key to more accurate readings for me.
Hang in there! You’ll learn the nuances of your own particular receiver and sensor. I wouldn’t call accuracy the hallmark of any of the current generation of CGMs, but the trend data is invaluable and when it is running with 5 to 10% of your fingersticks, it’s an absolute dream.
I’m in agreement with FHS… let it chill in your sub-q tissue (interstitial fluid) for a while before you judge it.
Also, make sure you’re drinking plenty of water to keep the sensor moist. I found that the better hydrated I am, the more accurate Dex is.
Hang with it. There is a post in this group from a while back about when to calibrate… if I remember correctly, don’t calibrate when your fingerstick shows above 200. You want to calibrate when you’re lower… like closer to 90 I think? You will want the sensor to be most accurate when you really need it… low and/or dropping lower rapidly. Anywho, what I’m wondering is how your calibrating.
Best of luck-
~a.willie
I go to the menu, and select Enter BG, enter the blood test number, then hit ok. My trainer suggested I calibrate before I eat. Yesterday, I calibrated when I tested and was at 102, but the sensor said 175. That scared me, I felt normal, but the sensor said I was high, is that a good time to calibrate? When your BG and the sensor are SO far apart? You guys helping me is SOOOOOOO appreciated!!!
That’s not unusual for a new sensor, at least from my experience. Those are times when I honestly feel like the Dexcom is just a random number generator and all I’m looking for is a sign that the sensor is settling in before I worry about calibrating for accuracy.
Overall, when you are calibrating, I wouldn’t really worry about what the Dexcom says. When you are calibrating, you are telling the Dexcom what your BG is and giving it a reference to go on. It wouldn’t know any other way.
Calibrate when your BG is stable, regardless of when that is. If you feel like, or the Dexcom is showing you that your BG is changing rapidly, you won’t get a good calibration, at least from my experience. It could be before meals, between meals, before bedtime, whenever. I calibrate, and make sure the Dexcom has a chance to take at least one reading before I do anything that might lead to a change in my BG.
The trick is timing your new sensors and calibrations so that they occur during times when you’ll most likely have stable BGs.
I am having the same problem. When I get my morning fasting reading, it is usually fairly accurate. by mid-morning, it is off 30-50 points. when I enter 2 readings within 15 min ( as suggested by DEX) it gives a “near” BG reading, then turns around, and “misses” the other way. I feal it is almost a random number generator, but have nothing else to hope for as a back-up for the Navigator unit that was ALWAYS within 10 points!!! I know the technology with the DEX is electrical, and I know I have a pretty high electomagnetic “force” from my body. Could this be interfering? All Dex can do is tell me to replace pods… I have also told the sensor to deactivate, then reactivate, and it still does the same thing.
New users of DexCom equipment need to adjust their expectations and learn the ins and outs of the system. It takes a while for a newly inserted sensor to “settle in” and provide useful information. There is a biological process that occurs between your body and the sensor probe. That process is very variable. DexCom schedules two hours for this process to stabilize and then asks for the calibration. This is the normal expectation. However, experienced users recoginze the “settling in” period is variable and many times the sensor just does not take ever. You will learn the ropes. When a sensor does not take, I have been advised to allow 24 hours. Then I enter 3 calibrations each 15 minutes apart. If the sensor does not “settle in” and provide useful readings after entering the three readings, I report this fact to DexCom support and request a replacement sensor. The DexCom software has a feature that will allow data to be uploaded from the receiver directly to DexCom computers where they will be able to evaluate the sensor performance. So far I have never had any trouble with DexCom replacing sensors that are not working. I urge you to keep an open mind about the system. Please relax and allow the DexCom support people to guide you through the learning curve.
Here are some tips that I have learned here, some that were stated above. Only calibrate when your BS has been stable for 15 minutes. Someone here said that it is better to go off of a calibration that is 18 hours old than put in a bad calibration. It is quality, not quantity that counts.
If you have bad calibrations in, restart your sensor to clear them out.
Like Aaron said, Dexcom suggests doing 3 calibrations 15 minutes apart to help get the sensor back in line. I have done that a couple times and my BS will start to move rapidly so I will try again when it is stable. If you call with a problem, that is one of the things they will have you try to do.
Make sure that you are well hydrated - since it is summer, you can be a little dehydrated and the Dex won’t read as well.
Even though Dexcom recommends using the abdomen, some people find they get better readings on other areas. Try different spots to see what works better for you - some people use arms or love handles. I pretty much only use my abdomen because of not having anyone to help me get it on other spots, but a friend suggested using lower abs. Even though I was getting decent readings before, they are really good now. When I was using the upper part of my abdomen, I would always get bad readings on the right side for some reason.
Peruvianpasohi, I am not sure if this was a typo, “when I enter 2 readings within 15 min ( as suggested by DEX),” but Dexcom actually recommends 3 readings 15 minutes apart. If you really are doing 2 within 15 minutes, that could be part of your problem.
I had the same problem for the longest time…and was being awakedned in the middle of the night to alarms of a bg of 50 and when I tested it was 150, which was way too far off for my comfort. Oftentimes, it was off by as much as 200 pts! When I called Dex, they suggested when I first put in a new sensor, to wait 2 hours before the initial calibration which is my standard mode of operation since, and also, (I believe FHS has pointed out) I find the accuracy is better the longer the sensor is in…sometimes if I go past 7 days the accuracy improves tenfold! Stick with it…you’ll get there!
This happens to me as well, stable and accurate fasting BG followed by erratic and inaccurate mid-morning readings.
What I personally found is that my early morning to fasting BG is very stable. If it does change, it’s a slow, steady change that the Dexcom can easily track with good accuracy.
After breakfast, my BG go through rapid and variable changes as my food, insulin, and exercise are all affecting my BG in various ways. This creates havoc for the Dexcom since there is always going to be lag between your whole blood changes and the changes in the interstitial readings. The trend data are still good though, even if it does lags behind by 15 to 20 minutes.
After lunch, when I start to settle in to my day, my Dexcom hasa chance to settle in and track my BG with accuracy again.
Regarding the 24-hour stabilization period - I have noticed this as well. I now insert a sensor but don’t “start” it on the Dexcom for about a day. Then I start the 2-hour wait period at dawn and calibrate in the early AM when my BG is pretty stable.
I haven’t tried overlapping the timing of the sensors, but it would be tough to do with one transmitter, anyway. I figure that since the accuracy in the first 24 hours of a sensor life are bad anyway, I’m not going to bother with it. Back to frequent fingersticks.
That’s a great idea. It would save a couple of meaningless fingersticks at the start and any meaningless calibration fingersticks in the first 24 hours.
I think I would really miss the cheap entertainment I get from watching my Dexcom walk into walls, figuratively speaking that is. I’m easily amused.
You are! but that’s cool, especially for all of us T1’s, to be easily amused, that is! Gotta have a good sense of humore about it! I laugh at everything and anything having to do with the hardware that I wear on my bod!
I have never heard that restarting the sensor clears out bad calibrations. I know it doesn’t clear out good calibrations!
Restarting the sensor clears out all past calibrations, good or bad. Resetting the receiver allows data from the existing sensor to be processed as a newly inserted sensor. Although the transmitter sends signals as before, the sensor does not have the ability to identify itself and therefore the receiver cannot tell the difference between a new or an old sensor. The purpose of restarting the sensor is to clear any past information to give the system another chance to start fresh. This makes sense because the sensor having had time for the body to establish the conditions for accurate readings can process the incoming data without considering past out of spec information. If the sensor continues to send inaccurate information then, it becomes very clear that the sensor needs to be replaced.
Joyce,
Everyone is giving you great advice. Let me share my two cents worth, please.
- Follow the book - insert, wait the two hours, then one poke with two strips. (keep in mind two strips can be up to 20-30% apart themselves depending on the meter manufacturer, etc)
- Stick with every insulin dose and enter the finger stick in the Dexcom receiver. This actually improves the accuracy.
- Keep in mind, both FS and CGMs are tools. Only our bodies know for sure how sweet we really are. Patience and call Dexcom if you have questions. At the price we are paying, they need to help us all.
Jay
Thank you all! I feel like I’m wired for sound, having the OmniPod plugged in, and now this. My sensor was delivered yesterday, and yesterday my readings were pretty darn close for a change! All of your advice has helped me out, mainly to be PATIENT! Which is NOT my strong suit, but with this disease, are any of us really all that patient?? I’ve noticed alot of you go past the 7 days, don’t you worry about the risk of infection?
NOt necessarily patient, but unfortunately, frequently Patients! Infection…nooooo, bring it on!
I would add to all the good advice above that you should remember that One Touch and other readings are not infallible. I’ve done over 100,000 tests in my lifetime and I now view blood sugar readings as an indication and not an absolute. If my One Touch gives me a reading that looks odd, I make sure I’ve washed my hands and do it again. Chances are, the second test will be different.
I’ve been using the Dex now since December 2008 and I have had my share of bad sensors (always replaced by the company), but on the whole I view devices like the Dex as a godsend for people like me with an active lifestyle.