Dear Medtronic…

. . . you’d best be getting your shit together and releasing a CGM sensor that I can believe in. You have between now and when that new Animas/Dexcom pump+CGM combo comes to market in the US. I like your pump offerings — even if they have tried to kill me — but the CGM accuracy is just a joke.

Sincerely yours,

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6 Responses to Dear Medtronic…

  1. Scott S says:

    LOL! Too bad this offering is still pending Fatal (er … Food) and Drug Ass(d)ministration approval … maybe in 10 years or more, we can have this piece of crap, too.

  2. Marcus says:

    While I agree that the Medtronic sensor is inferior to the Dex, I’ve been tweaking how I use it lately and have gotten better results.

    Simply put, I’ve gotten religious about never never never calibrating unless I’m 100% sure I’m flat lined stable. Granted, that’s not often, and it’s also more of a pain than the Dex. But when I do that, the reliability is comparable to the Dex.

    I just like carrying 1 device so I’ve worked hard to get the Medtronic to be better.

    This means that I often will have the sensor stop pulling readings for a while as I wait to be stable, but more importantly, I can trust the readings when it is working.


  3. Cosigned! I know I’ll be looking into what sort of trade-in is possible once approval comes through in the U.S. If nothing else, I’m disappointed in Medtronic’s seeming inability to make the innovative leaps Dexcom and Animas strive for.

    And hot damn, I can’t wait to see gen-4 Dexcom in action!

  4. Jeff Mather says:

    Marcus: I too have tweaked how I use the MM Sof-Sensor, and often I get very good results that I can believe. Then there are other times when I follow the same procedure that you describe of only calibrating during stable periods, but the results are beyond messed up. (I’ve even restarted sensors that were giving bad results, hoping it was just the curve-fitting/calibration that was messed up . . . all to no avail.)

    I’d say about 70-80% of the time I get “acceptable” results – though I still don’t believe it during exercise – but that other 20% of the time makes me want to throw it away.

  5. Nancy says:

    Not having diabetes…..does the sensor give more accurate readings when you aren’t anaerobic rather than sedentary? Just a question. Does build up of lactic acid affect your readings and the reliability of the CGM?

  6. Jeff Mather says:

    Mom: I’m not 100% certain under which conditions the sensors are most accurate, but I suspect the inaccuracy have more to do with the rate of change in the blood sugar than anything that’s going on in the muscles themselves. The sensors measure “interstitial glucose,” which tracks blood glucose but is detected between the cells in the fat layer just below the skin. Because of this, there’s a delay between changes in blood glucose and changes in “ISIG.” Usually BG changes are slow, but when it’s really moving, the ISIG lags a bit. And because of the curve-fitting algorithms and the built-in delay in reporting ISIG changes, the Medtronic CGM can be really inaccurate during exercise (at least for me).

    I hope they work on that. At the very least, I hope they provide an option to plot the raw ISIG values instead of the interpolated BG values. I would rather see a much noisier graph when I know that my BG is changing a lot than wonder what’s actually happening as it tries to fit those spikes and dips to a smooth, continuous curve.

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