Restarting Dexcom G6 sensors – Updated

Awhile ago, I posted a page about how to restart your Dexcom sensors to last beyond 10 days. There’s need for some updated discussion on the topic.

For clarity- let’s take one quick aside to make sure we are clear on TERMINOLOGY before going in deeper.

  • Reset = resetting the clock on the transmitters so that you can use them beyond 110 days that Dexcom officially ends them at. If you reset a transmitter, you get another 110 days to run that battery down to nothing. When the battery dies, no amount of resetting will help. It’s dead.
  • Restart = term for restarting a sensor session to last beyond the 10 days that Dexcom officially ends them at.

So to be clear…sensors can be restarted, transmitters can be reset. BUT…if you say “restarting a transmitter” or “resetting a sensor”…I may think that you are confused about what you are actually trying to accomplish. I will try to be careful to always use reset and restart to help you follow along exactly which parts I’m referring to.

Ok, now that we have that out of the way, let’s talk about some recent developments on the G6 system. First, a quick description of the products available as there are a few new ones out there.

G6 transmitter

Most G6 transmitters, that we are all familiar with from the start of distribution in June 2018, are fairly flat on top, with a small round indent on the fat end of the transmitter. The transmitter IDs start with 80xxxx.

(Quick note about transmitter IDs: the transmitter IDs could be different in different markets/times…it’s not like Dexcom is sending me a pamphlet to let me know their whole scheme. So…if in doubt, go with the visual indicators of how the transmitter looks and is shaped.)

Those transmitters can be reset using the Reset Transmitter app (instructions here), or Spike/X-drip+ apps.

Those transmitters work offline with all versions of Loop app.

G6 “81” transmitters

Dexcom started sending out transmitters with IDs starting with 81xxxx. At first they seemed mostly Outside US, but now they are in US market too. They look very similar to the transmitters described above. The 81xxxx transmitters will not usually restart sensors using the 15 min, no code method. These transmitters have the more aggressive trauma check discussed below.

Those transmitters can be reset using the Reset Transmitter app (instructions here), or Spike/X-drip+ apps.

Those transmitters work offline with all versions of Loop app.

G6 Firefly transmitter

The G6 firefly transmitter is a “new” transmitter that Dexcom has quietly started to ship out in the US. There’s no formal announcement from Dexcom about this new transmitter. The transmitter ID for G6 firefly starts with 8Gxxxx and the transmitter is visually different than the old ones. There is (1) a kind of bump/hump running along the top of the transmitter’s length where the word “DexcomG6” is printed, (2) bigger, bolder writing for the transmitter ID on the underside, (3) lack of “FCC ID” printed on the transmitter’s underside, (4) a little oval indent surrounding the metal contact points on the underside of the transmitter, and (5) a little groove surrounding the perimeter of the transmitter (like where top-half and bottom-half join). There’s a photo below of the G6+ transmitter which looks very similar to the G6 firefly. The good news is that the new transmitter does seem to have a longer range and pretty strong connection. The changes to the design also probably mean quicker manufacturing for Dexcom…so maybe Canada might finally be able to get the G6 system, too?

The bad news? This is not yet direct-to-watch.

These transmitters cannot currently be reset.

These transmitters cannot currently work with Spike or Xdrip+ apps (to my knowledge…and I will update this when someone does make them compatible).

These transmitters can be used with Loop offline, so long as you built/updated your Loop app after July 18, 2019.

G6+ transmitter

In South Africa, Dexcom is rolling out a new G6+ system…as part of that system, there’s the G6+ transmitter. It has all the same features of the G6 firefly transmitter described above but says “DexcomG6+” on the top. The transmitter IDs for the G6+ start with 22xxxx.

(side note about the G6+ system overall: 14 day sensor sessions and one hour warmup are also part of the new system they are getting in South Africa)

These transmitters cannot currently be reset.

These transmitters cannot currently work with Spike or Xdrip+ apps (to my knowledge…and I will update this when someone does make them compatible).

These transmitters can be used with Loop offline, so long as you built/updated your Loop app after July 18, 2019.

Restarting Sensors: that 15-min, no code thing

So all that talk about transmitters is to let you know that some of the restarting options may need to change for you. The G6 firefly, the 81xxxx, and G6+ seem to have new more aggressive check(s) for “insertion trauma” signs of a new sensor to prevent restarts.

I know the internet had a lot of users that used the “stop sensor, do 15 minutes of no-code, stop sensor, do old code for 2 hours” method of warmup. That 15-min, no code method is prone to failure, and will have even more failures with the new transmitters especially.

Why? Dexcom is looking for signs during warm-up that show that your sensor is new. With new sensors, you’d expect to see some jumpiness in the BG data as the new sensor wire gets acclimated to the new in-body environment. The data during warmup is not the quiet, calm BGs that a settled-in sensor has. Occasionally, an insertion can go so smoothly and BGs happen to also super stable for 2 hours…that Dexcom’s algorithm perceives that the user was restarting because the trauma signals aren’t strong enough. We’ve all probably had that happen once or so…”But wait…I wasn’t restarting”. Congrats, you had a smooth insertion, with stable BGs. Your potential reward? Get another new sensor and show some real trauma this time.

The sure way around “no restarts”: Bluetooth Unpaired method

The only way for sure around this trauma check that I have found on both new and old transmitters alike is to use the old Option 2 method from my original post. Let’s call it the “Bluetooth Unpaired” method from now on.

HUGE IMPORTANT POINT: You must start and finish this process before your current sensor session is scheduled to end. In other words, if you see you have 2 hours left on your session, you’re too late.

The detailed procedure for the “Bluetooth Unpaired” method:

(Start AND finish the whole process before your existing session was due to end!)

1. Wait for new BG to come in and then wait about one minute. Doesn’t have to be exactly one minute…just enough of a little pause to make sure the transmitter is done talking to the app. If you session already expired, just start with step 2…no big deal.

2. Forget/delete Dexcom from Bluetooth list in phone’s settings. iPhone users, tap the little “i” next to every Dexcom ID in your bluetooth list and forget the pairing(s).

3. “Stop Sensor”, “New Sensor”, enter code, “Start Sensor”

(If you are a Loop user, delete your CGM in Loop settings here…we will add it back at the end of this process. If you forget to delete your CGM in Loop settings, you won’t see a pairing request in Steps 5-6.)

4. Wait 2 hours and 5 min for the warmup to finish. Do not accept any pairing requests during that time. You’ll probably see “transmitter not found” display on the Dexcom app during this time. You can use your phone as normal during this time, but I advise turning off Dexcom app in the Notifications section of your phone settings so that you don’t keep getting pinged every 5 minutes.

5. After the warmup wait, open Dexcom app and wait for pairing request.

6. Accept pairing request. You may see “signal loss” message for up to 5 min after this setup.

7. BGs and fresh 10-day session should appear after that signal loss clears in five minutes.

(If you are a Loop user, add your transmitter ID back into Loop settings here.)

Microwave/Receiver Method still work?

So far in my experiments, I have not been able to use the old “Option 1” method (the microwave or receiver method) on the newer G6 firefly, 81xxxx, and G6+ transmitters (*UNLESS I FIRST did a restart using the Bluetooth Unpaired method…see SUPER INTERESTING LOOPHOLE SIDE EFFECT paragraph below). I also could not get the 15-min, no code method to work with the new style G6+ or G6 firefly transmitters.

So, if you want to use your receiver restarts again with new transmitter styles…make sure to read below.

Why would you want to do the receiver restarts? Seems like hassle to you? Most people choose this method because you continue to get CGM data during the restart wait.

If you don’t own a receiver or don’t care about the 2 hours without CGM data, then go ahead and stick to the Bluetooth Unpaired method described above.


Once I did that Bluetooth Unpaired method for a restart though, oddly that seemed to disable the trauma checks in the system/app long term. I have been able to use the receiver restarts just fine again, so long as I had already done one restart using the Bluetooth Unpaired method. I can now even simply stop a session and restart it directly…without any deleting of transmitters from BT or 15 min, no code…basically stop/start works just fine on its own.  The app becomes pretty much like the G5 app in terms of simplicity of restarts. <—- that’s a really big deal if you value simple restarts. I’ve had one other person confirm their app behaves the same as I’ve just described using an G6 firefly after she did a Bluetooth Unpaired reset once. SOOOO one confirmed with G6+, and one confirmed with G6 firefly…I am testing this method on the old style G6 transmitters now to see if the same loophole can be created with those…I’ll let you know in a day or so. For some reason, I’d never found this loophole before. Maybe it wasn’t there on the old transmitters, or maybe I never looked hard enough.

(*By the way, once I deleted the Dexcom G6 app and reinstalled it, the trauma checks came back to life, and I had to do the Bluetooth Unpaired method once again to get rid of “no restarts” messages.)

Safety Precautions

As with all things DIY…use COMMON SENSE and SAFETY FIRST. The accuracy of Dexcom sensors will decrease over time and the more you restart, the more this could be a concern.

After you see your CGM readings start again on a restart, make sure to do a several finger checks regularly with your glucometer to check for accuracy.

Don’t extend a sensor session beyond its accuracy…ESPECIALLY IF YOU ARE USING AN AUTOMATED INSULIN DELIVERY SYSTEM. No amount of money savings is worth automated insulin delivery on a sketchy sensor.


Final note, good thing I’m not charged per sensor session by Dexcom. I think I did about 50 sessions on these tests just to make sure of everything.




10 thoughts on “Restarting Dexcom G6 sensors – Updated”

  1. Hi
    Thank you sooo much with all these methods- it helps us cash paying Dexcom users such a great deal!

    I am from South Africa, and currently using the 14day sensor. I’ve tried every restart option available but nothing worked- not even the ‘forget Bluetooth’
    All three 14 day sensors have the same code- which is interesting.

    Will be so grateful if there is a restart option on this on. The warm up is only one hour- which is great

    1. I did all my testing on the G6+ South African app and transmitter…and redid all the tests four times to make sure. And had three other people test it on their systems…so far all successful. If you got a failure, please check the procedures exactly and note where you did something different. Android phone? Different timing? Didn’t start with active session?

  2. Katie;
    I can’t thank you enough for your super wonderful instructions – all across the board, from Loop Docs to tidbits here and there. I began coming across your name (not that it didn’t exist previously, but I had just come across it then, at the time two years ago). On you tube on how to replace transmitter batteries; resets and restarts; Looping; Nightscout to Tidepool and more in between! It is so nice to have “options”. I hadn’t really put the information to use, but was “curious” and was learning more about other opportunities that existed. Early Fall of 2018 I was doing research on Looping but ended up putting it aside because I had an “older” Medtronic 623 but it had the “new” version or software security update and I wasn’t interested in spending any extra amount of money trying to chase an older “usable” Medtronic pump down and take any chances if it would work or how long it would work – how much life was left in it. I would have taken a chance on the Medtronic pump I had (that sadly wouldn’t work) but wasn’t willing to go beyond that.
    Most of the year of 2019 I was in Clinical Trials for the Tandem TSlimX2 insulin pump with InControl software working with the Dexcom G6 but in June 2019 I happened to search online again and then found a YouTube video (another OmniPod Looper had done) and that Loop was now compatible with OmniPod (which I had been using the previous four years) so while the Trial was still active; my wife and I decided to take the plunge and purchase a MacBook in order to build the Loop app; get the Apple programmers license; etc. you know, the steps that were listed and many thousands of people have done before I did and of course I still had “older” OmniPods yet to use and was very happy to use them with Loop.
    The Clinical Trial was completed around December 13, 2019 but I ended my Trial early on October 28, 2019 because I was able to get Loop together and working for the OmniPod and couldn’t wait to use it! And had it running when I turned in my remaining Clinical Trial supplies on October 28, 2019.
    Thanks for taking charge and sharing your experience and expertise with so many (and taking such great care of Anna) and the rest of your family too!
    Again, I can’t thank you enough!
    Blessings to you and your family!
    PS-I also recently stopped and thanked Pete Schwamb – my kids go to college in the town he lives!

  3. So I am using what I believe to be the Firefly transmitter with the dexcom app on a Samsung Galaxy S10+. Whenever I impair my transmitter in BT settings, it repairs in less than a minute. I’m assuming this is a something in the dexcom app that automatically pairs tbe 2. I can’t find a way to stop it. Any ideas?

    1. Android phones behave a little differently than iPhones, and unfortunately not all android phones behave the same. Some will automatically re-pair bt connections without asking for confirmation (like happens in iPhone). You might be able to find a setting in the phone to keep the bt off…but it’s hit and miss with androids unfortunately

  4. Hello, my transmitter is G6 with serial number 8J****. I’m using it with xDrip. I’m confused if this is firefly or not, and will I be able to reset it after 3 months?

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