I just started a week long dexcom trial yesterday. I was immediately impressed with its accuracy (within 10 points from finger stick). However, as today progressed it got further and further away from my finger sticks and is now about 30 points off! It just alerted that i was low, 69, and when i did the finger stick i was 101. Is this typical? Any way I can get it back to its initial degree of accuracy? Even if I cant, I still love this thing!!
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It really depends on many things. Generally your dexcom (I call mine dexi) will lag about 10- 15 minutes behind. So if you are rising or falling quickly it will take a bit for it to catch up. A 30 point spread is not unusual in these situations.
Second, the longer you keep the dexi in the more accurate it will be up to a point.
third, overnight mine will usually run a little lower. It makes sense since my heart is not beating as fast, the fluid being measured is running a little slower and the glucose concentration can be a little slow to catch up. especially where i wear mine (arm).
Remember the finger stick is the current gold standard for in-home treatment. But even it is subject to a range. all automatic measurements tend to be more accurate within standard range. highs and lows will make the device be less accurate.
Good luck I love mine.
I usually find my Dexcom to be more accurate as the days go by. If you are on day two, just give it some time. You will get used to the pluses and minuses. I don’t want to be without mine.
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Becca8122, are you calibrating your Dexcom correctly:
- Only when your BG is level (horizontal arrow)?
- No more often than twice daily?
Calibrating when your BG is not steady can lead to inaccuracy.
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@rgcainmd thank you for this bit of info. I calibrated 4 times AND disregarding the arrow!! I probably confused the heck out of it! I wasn’t sure if I was supposed to put my finger stick reading in the dexcom every time or just the two times that the dr. specified. I’m on the right track now. It hasn’t been off more than 12 points since I’ve started following directions! Ha!
I love this thing!!
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Directly from Dexcom’s site -
"You should calibrate when the system requires it or if the CGM reading is inaccurate. You can calibrate when you are asked for the two start-up blood sugars, and whenever the sensor is inaccurate. Inaccuracy is defined as when the difference between your sensor glucose reading and blood glucose value is greater than 20% of the blood glucose reading and blood glucose value is greater than 20% of the blood glucose value for sensor readings > 80mg/dL or greater than 20 points for sensor readings < 80 mg/dL.
Beyond the recommendation above, I find it best to only calibrate when your blood sugar is steady (i.e. Not after meals or exercise). Often, I wait sometimes hours to put in my calibration reading.
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Dexcom staff have said it’s OK to calibrate when the arrow is trending up or down (in addition to the horizontal arrow), but I NEVER have my daughter do that. I’d rather wait until the arrow is horizontal which means she is “feeding” her Dexcom the most accurate information possible (considering how inaccurate BG meters are allowed to be, that is!) Just because a slow trend either up or down is better than a straight arrow up or down doesn’t mean that you shouldn’t hold out for the very best: a horizontal arrow.
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I’ll generally wait for stable conditions, though I do get tired of the persistent blood drop icon on the receiver, and have found these two things to be useful:
- Since I can spare the extra strips, I’ll do 2 or 3 measurements and compare and maybe average them before entering the number for the Dex calibration. I do this especially at initial calibration of a new sensor and after getting the strip data will figure out what the most likely “real” bg value is, and enter that twice.
- If you can’t wait for stable conditions, or the sensor is starting to act up (like toward the end of week 2 for me), you can take 3 measurements at 15-20 minute intervals and enter those. This was explained to me by a Dex rep and has worked reasonably well in such situations. (Though when your sensor is giving out there’s only so much coaxing along that you can do.)
I always hold out. Partially because I don’t trust any meter. The variance from test to test is just way too wild, but that’s another discussion for another day.
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We also always hold out for the horizontal arrow. Like I said in a different thread, the Dexcom will not spontaneously combust or cease functioning if you don’t enter a result from a meter right away after the red drop appears. Much better to wait than to enter a value that is going to screw up the accuracy of the Dexcom reading!
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Coincidentally just got back from Endo. a1c on my Clarity report was 6.0. Blood test a1c was 6.1. In Dexcom I trust!!!
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I’ve also stopped stressing over when I calibrate the first readings, as in trying to space the second one exactly 12 hours apart. The sensor I have on now I started at about 2 pm and I wasn’t about to get up at 2 am to enter the second calibration. Did it when I got up the next morning and it’s been extremely accurate. I agree, best to calibrate when you have a straight arrow and not after eating potato chips!