# Dexcom out-of-range calibration?

**URL:** <https://forum.fudiabetes.org/t/dexcom-out-of-range-calibration/3452>\
**Category:** C/GM\
**Tags:** dexcom\
**Created:** [February 8, 2018, 12:59am UTC](https://forum.fudiabetes.org/t/dexcom-out-of-range-calibration/3452 "2018-02-08T00:59:50Z")\
**Posts on this page:** 3\
**Page:** 2

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**Author:** ![Chris](https://yyz2.discourse-cdn.com/flex030/user_avatar/forum.fudiabetes.org/chris/32/382_2.png) [@Chris](https://forum.fudiabetes.org/u/Chris)\
**Post date:** [February 8, 2018, 8:51pm UTC](https://forum.fudiabetes.org/t/dexcom-out-of-range-calibration/3452/21 "2018-02-08T20:51:17Z")

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> [@Katers87](#):
>
> This would indicate that, for whatever reason, the relationship may be less linear for these people.

The unfortunate answer is that it depends heavily on the coatings that they use and the maximum current capacity of their system, so it is likely that with each generation the resulting linearity is getting better as they learn more and improve their system. Generally speaking, sensor systems that measure hydrogen peroxide on an electrode will be linear until about 200 mg/dl. Then they lose their linear relationship. With that said, with the right coatings you can improve this dramatically.

The Abbott product is linear through the whole physiologic range which is why they say you don’t need to calibrate it.

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**Author:** ![Katers87](https://avatars.discourse-cdn.com/v4/letter/k/a9adbd/32.png) [@Katers87](https://forum.fudiabetes.org/u/Katers87)\
**Post date:** [February 8, 2018, 8:57pm UTC](https://forum.fudiabetes.org/t/dexcom-out-of-range-calibration/3452/22 "2018-02-08T20:57:57Z")

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Do they change the coatings for the same product? Meaning, did my box of G5 sensors from 2 years ago use the same coating as the sensors in a box I just got? Or is it possible they could have changed the coating since then?

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**Author:** ![Chris](https://yyz2.discourse-cdn.com/flex030/user_avatar/forum.fudiabetes.org/chris/32/382_2.png) [@Chris](https://forum.fudiabetes.org/u/Chris)\
**Post date:** [February 8, 2018, 9:37pm UTC](https://forum.fudiabetes.org/t/dexcom-out-of-range-calibration/3452/23 "2018-02-08T21:37:45Z")

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They absolutely could change. And when I say coatings, I mean more than one, we often used 3 or more coatings applied in sequence to get the best performance depending on what we were tuning for. However, due to manufacturing concerns, they probably are only likely to change when they come out with a new product. That is unless the engineering team could make the case that the disruption to manufacturing would be offset by the product gains.

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