Ten days in… Two sensors end

Ten days come to an end, and the first and most obvious, difference between the Dexcom devices and the rest is immediately obvious.

The Dexcom sensors have come to an end, while the rest keep going until 14 days.

This might not seem like a big issue, but for quite a few people, the ability to know that on the same day of the week, at more or less the same time, they will change their sensor, provides one less thing to worry about.

Sadly this isn’t the case with Dexcom.

And what of the other sensors?

The Aidex and Medtrum remain well attached, and continue to give readings.

The Libre2 fell off within 3 hours, and while I was able to report the issue within 15 hours, the replacement was only sent from the warehouse 9 days later, so there’s no Libre2 data in the final reckoning.

The Glucomen Day also gave up the ghost after 3 days, with the app stopping the sensor session. Glucomen believe it was due to the sensor movement and have issued a replacement, and as I had a spare, I have added that and will at least have some data, if not all, consistent with the same fingerpricks.

Any preliminary view on the Dexcom data?

There’s a fair bit of analysis to do, but we do have some preliminary MARD-F (MARD from Fingerpricks) data.

  • Dexcom ONE: 9.7%
  • Dexcom G6: 12.1%

There’s also the Mean Relative Difference, which gives a rough indication of bias.

  • Dexcom ONE: -2.3%
  • Dexcom G6: 8%

In this n=1 experiment, the Dexcom ONE has performed slightly more closely to fingerpricks, whilst showing a tendency to produce values slightly below them. The G6 was further away and tended to produce higher values.

Error grids and 20/20 data will be produced in the final summing up at the end of the experiment.

So can the ONE be restarted?

As the ONE is available on the prescription tariff, there should no longer be a need to restart, however, if you were to find yourself not having a sensor and needing to get readings, then the answer is “Yes, it can be restarted with the Dexcom ONE app”. And it still takes 2 hours to warm up.

And there we have it. The mid-experiment update. Keep watching for further information.


  1. Thanks for doing this for the community.

    Please note that for the majority of T1Ds, who all live outside the USA, issues around funding of sensors are entirely different.

    For us the major benefit of longer sensor life, or being able to restart, is cost.

    It’s a real shame that the Libre 2 won’t be included in the results, as it’s the main contender for being a viable (acceptably accurate) alternative to the price-leading Dexcoms. Interesting that the One reads lower. I guess it is trying a bit harder to predict based on slope (to offset delay).

    • No, I don’t think the One algorithm is any different to the G6. They’ve just removed the calibration ability from the software. If you look back, it almost never went in to the G6 in the first place and was added as a sop to users.

      I understand your point about outside of the UK. The driver for this experiment was UK health care provider availability, hence the comments associated with it.

  2. Many thanks for doing this research for us all – particularly timely as the UK national press is publishing more articles on Dexcom being “available to all T1s” over the last few weeks.

    From a personal point – would be interesting to see the Dexcom One matched against the Libre 2 data if you finally get that back on and running as L2 is my current ‘known’ sensor with its pros and cons, the Dexcom one being the probably next option if and when it gets added to the Nottingham Formulary.

    Thanks again for all your work and info

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