One of these things is not like the other - A discussion of CGM and Meter accuracy

[Eric]

@bkh

My guess is that you had a rising BG, it leveled off a bit and then started running higher, so you took a nice big IV bolus and 5 minutes later your BG was around 103-105 but the CGM hadn’t picked up this sudden change because of the lag in measurements of interstitial fluid, which gave you a good opportunity to take an outrageous photo. The problem, of course, is that folks who don’t know you and don’t know better could draw a wrong conclusion from the photo depending on the true explanation behind what we’re seeing in the photo.

I am not deceiving anyone like you are implying. Why would I do such a thing? I have spent two years here with nothing but the goal of trying to help others, not to deceive them.

@bkh

So, Eric. I just have to ask what’s the full story about the photo of the two BG meters and the CGM.

So you want the context of what happened?

The Dexcom alarm woke me up at around 8am, beeping a high alert. I did not take ANY insulin at any time between when I went to bed and several hours after that picture.

I looked at the Dex when it woke me up, and I knew immediately that it was wrong.

I went downstairs and checked with the meters. First with my Contour, and then just for laughs, I immediately checked with the FreeStyle. The 3 readings being so disparate was comical to me. I took a pic because that is the sort of crap I see all the time, and thought it would be an interesting post.

Not only was there no IV shot involved, there was no insulin of any injection method involved for about 8 hours, other than basal.

@bkh

I find it hard to believe that the CGM shows your BG rising for nearly an hour, from 50 to 167, if you were just hanging out at a nice steady 103. What really happened?

Your accusatory tone was rude AF.

I would never try to deceive people here. I love the people here and only want to help them.

There are at least 3 people on this site who have a somewhat disparaging view of Dexcom. One of the people thinks so poorly of it, they have quit using it all together.

What do the 3 people have in common? They all test at least 20 times per day, and they have A1C’s between 4.7 and 5.3.

So you figure it out. What an amazing coincidence. Those of us who test enough to be unimpressed with the CGM are the ones with the A1C’s in that range.

@bkh

I find it hard to believe that the CGM shows your BG rising for nearly an hour, from 50 to 167, if you were just hanging out at a nice steady 103.

Well there it is. The fact that you find it hard to believe makes it clear where the problem is.