Sunday, May 20, 2012

Meter madness, jumping to conclusions...

I'm a little excited about the new meter because it came with a lancing device that has been highly reviewed by other glucose checking enthusiasts.

The Fast-clix* lancing device is pretty different. It has a rotating drum of lancets that allow you to change lancets with the flick of a switch, and unload your lancets without exposure to the sharp points. And, you can prick your finger in one easy motion, without "cocking" the device. It is so fancy that I couldn't get it set-up and use it without reading the directions... that's pretty special. After doing this finger poking thing for 25 years or so, you'd think that any device that came your way would be super simple to figure out. Well, this one required just a tiny bit of study.

So here's the creepy bit... (what does this number mean?)

My sensor was reading 170 (post french fry experiment). I Accu-cheked with the new meter and it said I was 240. I was pretty surprised to see such a difference (and, of course my mind went wild wondering if my meter that I use for calibration has been wrong all along, and I've been running 70 points higher for the past couple years).

I tested again, 204. Not good, that's still a decent difference from the CGM and the previous test. I tested again, 213. I took that one as my correction number and delivered a correction.

So, maybe an hour later, after dinner, I test again, 129. That was a fast drop, eh? I still have 2.5 units on board. Did I overdo my correction? I haven't even bolused for dinner yet, maybe I won't. Oh, that's right, when I was over 150 in the late afternoon I turned my basal up, and that's probably what's causing the faster drop. All this with a new meter in my life. 

With this new paradigm, I realized that my CGMS sensor is only as good as the meter that calibrates it. I sometimes wonder if my meter is entirely accurate (which we all know, they don't really have to be), and what impact it would have on my overall control to have a legitimately accurate calibration a couple times a day. Just something to think about. It's probably even worth letting integrated devices slip away, if they aren't accurate enough.

Recently, my sister (hi Ariana!) was trying to sort out some glucose mysteries and discovered that her meter was totally erratic and inaccurate. Well, that is not helpful when you are trying to respond to immediate problems... She got a new meter, and I hope that it offers a fresh compass in her quest for good glucose control.

This whole thing brings up a new question... I had been finding that I wasn't feeling any signs of hypo when I got down to 70s and sometimes 60s, when I was using my integrated One-Link meter. Today, I've been at 70-80 (according to my new meter) and I've been noticing my regular symptoms for hypos. It makes me wonder if I've been running higher than I think, all the time... if I calibrate my sensor off of a meter that runs high... and my data is all skewed downward. You wonder more...

My last at-home A1C was 6.7, but, my average blood sugar, according to my sensor had been 133 mg/dl. So, I would expect a 6.3 or so. Maybe my A1C is really telling me that my meter and sensor readings have been bogus to some degree. Maybe I really was averaging 15-20 points higher and never really getting close to hypos, ever. Always something to think about...

7 comments:

  1. My meter is definitely not accurate for me, even when it's very consistent; when I have blood draws in doctors' offices I check with the meter in the minute before or after the blood draw so I can see how far off it is. On a number of occasions, my meter has given a reading more than 30% off. Twice, the real blood draw showed I was hypoglycemic and my meter said I wasn't; that's why I treat when my meter says 90.

    Two things to note: various meters' accuracy is affected by different ranges of things that may be consistent. These things include things you'd never think about, like your vitamin C levels. I wonder sometimes if they also include medications people think are helping with their blood sugars.

    And, when you have a bad reading, it's not the meter that's responsible, it's the test strip.

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    1. Yeah, I like what you said about medications affecting readings. I've noticed something strange. In the AM, shortly after I take my handful of vitamins I have noticed that my BG goes up on my glucose sensor by 20-30 points, but on my meter it stays consistently the same all AM. I think there is a chemical change that shows in my sensor as higher BG, but isn't.

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    2. That's really interesting!

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  2. That's crazy that you could have been calibrating incorrectly all this time! At least there are some things like the A1C that can give a better idea of where you've been, but even those aren't as accurate as we'd like to think. Maybe it's a good idea to keep a few inds of glucometers and strips around, for a consensus every now and then...

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    1. Yes, I agree. I have been an exclusively One-touch meter user for as long as I can remember. It was almost spooky to fire up a different model and see what it said. That's why I tested 3 times in a row, lack of trust. Well, now I have 2 types of meters...

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  3. wow...I use the accucheck aviva and I notice how it's off, the higher I am. So I try to stay below 200 because I find that over 200, my meter can be off by 50+ points. I've heard that's more or less how they all are which totally...sucks. I always test twice in a row when I'm over 250 to give myself an idea of how much insulin to give. I have given too much insulin because of the meter displaying a 300 when subsequent checks showed 240, 250, 245. They really should work on this. We need better accuracy for meters and I think it's rather doable?

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    1. Sysy,
      When I got new strips for my OneTouch meter I compared them with the same sample and they were 6-10 points apart at both low and moderately high BGs. That was pretty reassuring. I have tried your 3 test trick and found that the variation did, indeed, vary about 20-30 points. So the meters where more similar to each other than they probably were to themselves? Interesting...

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