Extending the Dexcom ONE. Yes, you can.

• One of the first questions people in the WeAreNotWaiting community ask about new glucose sensors is “Can they be extended?”

In the case of the Dexcom ONE, the answer is “Yes” and you can do so within the official app.

Restarting is done exactly the same way as the G6. Pop out the transmitter using a blood test strip, leave it out for 20 mins, then reattach it and do the sensor start routine.

But it comes with an important caveat, and one that has significant consequences.

The Dexcom ONE is Calibration free, so where you might start a G6 in the official app and choose to either do it code free, or with a code, and then apply calibrations, this is not possible with the Dexcom ONE.

Why does this matter?

It matters for two reasons.

The first of these is that you need to retain the code you used to start it originally, which is a more trivial matter.

The second is that you have no choice but to have the system use the same initial insertion trauma calibration, which produces significant errors in the output compared to fingerpricks, as shown in the image below. The graph plots the same data points on the restart compared to the original start of the sensor, and it’s very obvious that the relative difference from fingerpricking in this case is much wider for the first three days after the restart, which makes it almost unusable. If you’re wondering why I’ve only got about 5 days of data on here, it’s because the sensors tend to become very unreliable for me on day 6 after restart, and that’s exactly what happened with the ONE.

What do we take from this?

At the very least, if you’re using the calibration code in an official app, be aware that the numbers the ONE puts out will not be very good.

And, if you want to extend the sensor by restarting, then use one of the flavours of xDrip. The firmware in the ONE is identical to that in the G6, and it will accept calibration in native mode, as shown in the images below. You just can’t do it from the hobbled app.

You can also run a no code start by entering the 0000 code and then calibrating daily from within xDrip.

Of course, if the firmware is identical, then in theory, at least the second Bluetooth connection must still remain, and the good people of the #WeAreNotWaiting community have already confirmed that the firmwares are the same and that the 2nd Bluetooth connection still exists and can be used. So you could, for example, use a ONE with an OpenAPS rig on the alternate Bluetooth connection.

Any blockers are purely down to allowed serial numbers in connecting devices. 

So, if you’re going to use ONE with the official app, you know what the constraints are. On the other hand, if you plan to use it with #WeAreNotWaiting tools, well, it might as well be a G6.