End of G6 transmitter question / starting sensors from T:slim

So, I just wasted a sensor because my tandem pump let me start a new sensor but then almost immediately cancelled the session because my transmitter battery was too low.

I always used to start my G6 sessions from my iPhone and, if my transmitter was near the end of its life, the Dexcom app wouldn’t let me start the process of starting a new sensor without pairing the new transmitter first. I stopped using my iPhone to start sensor sessions because more than half my sessions turned “manual” (i.e. calibration-required) even though I had entered the code using the “take photo” function.

Since switching to starting my sessions from my Tandem pump, I haven’t had any “manual” sessions, but today I had this new problem.

What happened was my sensor session ended so I started a new session by manually entering the code for a new sensor on my pump. Then I inserted the sensor, snapped in the transmitter and pressed start sensor and the pump showed the little green warm up pie. A couple minutes later, it said I had to replace the transmitter…effectively ruining that sensor.

I know that it’s possible to get a transmitter out using a blood glucose strip without pulling the sensor out but I didn’t manage it so I just pulled out the sensor and started with a whole new sensor and the new transmitter.

My questions are:

  1. Is this a difference between the Dexcom iPhone app and the Tandem pump interface? I.e. does the Tandem pump interface not have the feature that stops you from initiating a new sensor until you’ve replaced the transmitter when it needs replacing?

  2. Is it the iPhone “take a photo” feature that messes things up in terms of manual sessions and I wouldn’t have had this problem if I’d continued to use my iPhone but just entered codes manually? That is, was I throwing out the baby with the bathwater by not just stopping using the “take photo” feature but switching away from starting sessions from the phone entirely?

There are some more details to this story which I could add if this all seems inexplicable to people, but I feel like this post is already pretty long…

I always start my sessions on my pump. It just works better. No need for that photo code. It’s only 4 digits.
The phone takes over normally without any setting up.
You can start your dexcom sensor anytime before day 110.
You can start it from your phone but only before day 100.

However you have a second issue of battery low. Which both will reject, it doesn’t matter how many days, but if it’s less than 90 days, dexcom will replace it free.

I had this exact thing happen to me on day 104 however I already had my new one. And I was able to get out the old one and snap in a new one.

There is a method of filing off some of the transmitter to make it easier to get out, but I’ve never tried that.

My sensors are sent in groups. I get 9 sensors and a transmitter.
So i get about 1 extra session per transmitter. That way if there is a shipping delay, I can be ok for a while.

If your transmitter is passed 110, then forget it. Nothing you can do with it till someone figures out a new hack for the new transmitters.

Unfortunately the X2 pump does not track transmitter days. AND IT SHOULD.
I use xDrip to see day count, or Dexcom app should show days or start date of transmitter.
I also update it on calendar, and mark day 90 to make sure I know when close to end. XDrip is also helpful with day count of current sensor or when it ends (currently mine says ends in 4.5 days). I think closer to end will give date+ specific time.

I have a (Google sheets) spreadsheet where I track my sensor & transmitter usage. :man_shrugging:

Do the same thing for my infusion sets because I long ago reached that “certain age” where I soon forget how long I have been using a set or what sites on my body I recently used.

Thank you all for the feedback.

I’ve learned my lesson and have marked day 90 on my calendar.

Would it be fair to say that whenever the next sensor start AFTER day 90 is, I should use a new transmitter to be safe? That is, if I changed my sensor on day 89, I’d be OK waiting until day 99 to use a new transmitter, but that it would be unwise to start another sensor session with the old transmitter on day 90 or after?

The Dexcom app does tell me when the transmitter was started so it’s not hard to figure out what day I’m on. I’d just gotten used to the “idiot proof” feature of the Dexcom app telling me to use a new transmitter.

I’m pretty happy starting sessions on my pump and the phone app does indeed catch up. I’m still wondering, though, if it’s the photo aspect of the app that’s wonky or is it more the fact that when you have the pump and the app going together and you start from the app sometimes it just “loses” the code and turns manual?

BTW, I used the “take photo” function because I had no idea it would mess things up and it seemed kind of cool to me. But, obviously, it’s only a four digit code so there’s no actual convenience there. At this point it’s mostly a matter of curiosity to me since I know that starting from the pump works and I’ll stick with what works.

Did you call Tandem? They’ll replace the sensor for you. It’s a known issue and they don’t question it. Because they’ll replace the sensor, there’s little value in discarding it before you get the failure message… Unless you’re watching the days.

I have started on day 105 from my pump and it worked all the way through however the dexcom ap stopped collecting data at day110.
I don’t really use that much. I use my pump and the tandem ap to collect data for my doctor to see.
They are going to release a new version of that ap that will control your pump and sensors so maybe we can drop the dexcom ap.
At least they say this. However I also read that this will only be available to the newer pumps.

I actually called Dexcom and they’re sending me a replacement sensor so I’m not out of pocket. I just didn’t like tossing a perfectly good sensor because of the transmitter thing.

Technically, I think you could have removed the old transmitter and put new one on already inserted sensor. Then update transmitter id, and start new sensor.

Removing transmitter, while attached on body to sensor, can be done using bg strip or hair clip or guitar pick and many discussions here if you search for restart G6.
Its good to know how to do it, in case you get stuck short on sensors.

I restart sensors that remain accurate at end of 10 days, or do new sensor if its been “jumpy”.

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Correct. Its fine to have existing sensor start before day transmitter 90, and it should complete 10 days.
(Some say start ON day 90 is also ok.).

In the early versions of G6 transmitters, you could literally go until transmitter low battery. But current transmitters have updated logic to check day count.