CGM fails prime directive

[Spiker]

... due to user error

My Dexcom G4 with the Animas Vibe as receiver failed to alarm. Accuchek Mobile fingerprick reading, 2.8. Dexcom reading, 4.7. Or maybe 5.7. I can't remember and there is no way to recall the previous values after you calibrate (I used the 2.8 reading to calibrate).

However, it's my own fault. I have been terrible on testing and terrible on calibrating. Which is to say I have calibrated twice a day. So, here's the thing. In practice, I find, the Dexcom is very accurate, well within 1.0mmol/L of fingerprick readings, but only if do the standard 5-8 fingerpricks tests a day, and calibrate with each fingerprick reading. If I only calibrate twice a day, which is the minimum requirement, the readings on the Dexcom don't track closely enough to fingerprick readings.

So, user error. Not in the sense that the user didn't follow the manual. But in the sense that the user knew better than to follow the manual, but didn't apply this experience.

Hypo is fine, I am now waiting to see what the 100gCH is going to do to the rest of my evening. A very very very very mild preventive correction dose may be called for.

 

[DunePlodder]

It was a big discrepancy (especially if it was 5.7). I usually find that the lower the number the better the agreement. Once I get into double figures I treat my OneTouch Ultra readings with caution, often doing a second test after another hand wash.

Often just 2 calibrations seems fine, sometimes extra ones just seem to contradict each other - e.g. at lunch the Dexcom reads low then by evening it's high by a similar amount. I look at the graph & think if I hadn't calibrated at lunch it would be spot on now...

I think there is an element of "gut feeling" in this.

Do the results of calibrations always make sense to you? For example the Dexcom reading might be 6.0 with a steady horizontal arrow. A blood test shows say 6.8 but after calibration the Dexcom might show 6.3. Why not 6.8? Probably not a good example but I imagine you've seen similar situations.

Hope you've recovered from your hypo, and haven't "bounced" too high!

 

[Chas C]

I calibrate with every meal and before bed, so four times a day.

If I go high or low then I test again and if needed recalibrate, but this is not too often.

This seems to work for me, only on very very few occasions have readings been way out (often this is in the first day of a new sensor - or after reseting one).

 

[novorapidboi26]

this calibration sound like a real pain in the backside........

I suppose its worth it if you can prevent dangerous hypos.....

 

[Engineer88]

I must be lucky getting the accuracy on normal calibrations then...

@novorapidboi26 its only a BG check twice a day (can be before food or whatever)

 

[PaulinaB]

After the first 2-3 days when I calibrate more often than 2 times per day, my dex seems to be fairly stable with just 2 calibrations. Especially after the first 7 days, I can go through the whole day with just those 2 calibrations and no further testing. Whenever it asks for calibration I take a mental note "oh, I haven't calibrated it in 12h, it must be accurate"

I'd say it's all down to how your body breaks down the enzyme on the sensor. For me it seems to be very fast at the beginning, but the it slows down considerably, so the variations are much smaller.

Truth be told, I did had a similar situation, Spiker, where I felt very low (and was around 2.5) and dex kept saying I'm all good at 5-6. But a calibration usually solves the issue.

 

[Chas C]

I recalibrate because I test at every meal, after about 4-5 hrs mine always asks me to do a blood test anyway but its not always needed (i.e readings are close enough).