Changing a G6 transmitter

So its almost 3 months since starting on the G6, my transmitter is almost due to expire. I’m trying to work out how to best use the transmitter on the last few days so I don’t waste a sensor.

The dexcom site says the transmitter lasts 90 days. What happens if the sensor is not 10 days when the transmitter expires? Does it just shut off? Can i restart the sensor with a new transmitter?

I’m pretty sure it requires a new sensor. It won’t restart your current sensor session.

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The system will not let you start a new sensor unless it thinks there is 10 days of battery left.

All of my transmitter batteries have lasted more than 100 days. So changing sensor on day 90 has never been a problem for me, and I have been getting 10 sensors equals 100 days per transmitter.

The receiver will let you know by multiple notifications, in advance of the time it is time to put in a new transmitter. Battery “low” is not a sign (in and of itself) you need a new transmitter, there are other notifications that pop up too.


When exactly does the transmitter stop allowing you to start a new sensor? Does that mean as long as I am able to start the sensor, it will last the full 10 days regardless of where the transmitter is at. But that sensor will not be restartable?

You can’t start a new session after day 100. It gives you a hard stop after 110 days, the max transmitter life. Most of mine have died on their own before I got to 110, though.

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I use the G6 with the T-Slim and didn’t get a notice that I needed a new transmitter until the old transmitter was inserted into the sensor. I couldn’t figure out how to remove the transmitter without wrecking the sensor. Is there a way to do it?


Check your history for alerts. Should alert about a week or so before 90 transmitter days.
If you have xDrip or dexcom app, you should see transmitter start date or days used.
I hope Tandem will add feature to see days used in T:Connect nstead of just status of “battery ok”. I mentioned this on last call.

Search for restart sensor, and you will find instructions on removing transmitter.
Here’s one example.

So the best case scenario is to restart the sensor on day 99. I don’t know whether it’s worth inserting a new sensor on day 99 since (as @Jim26 mentioned above)you cannot restart it with a new transmitter. I wonder how the sensor knows it’s a new transmitter.

You can restart your sensor with a new transmitter. Same exact way you’ve been doing it, except this time you you need to change the transmitter ID on the pump and your phone. It’s just not in any of the official protocols since according to Dexcom, you can’t restart. Normally you would have to call Tandem for a replacement sensor, because theoretically, that sensor can’t be used once you get the “cannot start new session” error, because it’s full of a dead transmitter with no way to remove it.

Of course, we know better. So when you get the error, just pop the old transmitter out, change the ID in your settings, and insert the new transmitter into your existing sensor.

That’s my tendancy, just in case. You should be able to get away with doing it on day 100, though. I tend to do day 99 just to be safe.

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There are videos on Youtube showing how to remove a transmitter without breaking the sensor. Here’s two; the second is shorter but the first is better focused. The only tools you need are two used test strips.

When the transmitter is nearly done for, a sensor change will elicit a warning “this is the last session with this transmitter, make sure you have another on hand”. I think that it then will not allow you to start another new session with the same transmitter, EVEN IF that sensor fails early.

That’s how it’s supposed to work. It appears to be purely based on time since activating the transmitter, not on measurement of the battery condition. Sometimes the transmitter battery dies early. In this case you get a “transmitter battery critically low” alert. When this happened to me a few months ago, it only lasted a couple more hours.

If this happens, Dexcom will replace the sensor, since you cannot [are not supposed to be able to] put in a new transmitter with the same sensor.

However, the transmitter is guaranteed for only 90 days despite normally lasting for 110 days. A few months ago, my transmitter failed at 91 days. Dexcom replaced the sensor but not the transmitter. (I already had a new transmitter and sensors on hand, so it was an annoyance but no gap in coverage.)

Just a few days ago, my transmitter failed (“battery critically low”) at 58 days during a sensor swap. I explained that I didn’t lose a sensor, but they are shipping replacements for both sensor and transmitter anyway. I guess they just assume that “battery critically low” means a lost sensor.

Just recently – past couple of months I think – I no longer have to wait on the phone to report early sensor or transmitter failure. The last two cases, I just filled out the support form online. With the simple sensor failure, I also had to respond to an email with a couple of other questions – just the basic questions they ask on the phone. With the transmitter failure, I did not even have to do that.

I’m not sure how the above needs to be adjusted if you have restarted a sensor. I gave up on restarting because I seldom get good results after a restart. For me, sensors fail at 8 or 9 days about as often as they go a full ten days. I have built up a few to experiment with as a result …


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I just got a message to say my transmitter battery is going to expire in 2 weeks. I’ve still got 2 weeks until day 99. If I start a new sensor on day 99 (which is when the transmitter battery is going to go dead according to the message), will it last the full 10 days? Or is this message just a generic warning to prevent you from using it past day 100.

I’m pretty sure they’re generic. I haven’t yet found the notifications to be accurate. Unfortunately, you never actually know when it’s going to die until it does.

You’ll probably see an error code that says something “transmitter error: replace now”. You might not get another full ten days, but possibly so. It’s definitely worth possibly wasting the 2 hour warmup if it doesn’t last long, just in case it does last… At least in my opinion it does.

Unless you’re running Xdrip and can see the exact battery voltages, it’s all a crapshoot. Even if you can see the voltages, it only gives you a more educated guess.

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The hard stop is the day count, or sooner if actual battery goes too low. There is slow drain on transmitter battery from ime of manufacture, more drain once in use.

My last transmitter was DOA on first use, and had to wait for replacement.

Maximum days seems to be 90-112 days, if you start last sensor on day 90-102.
Warranty is for 90 days.

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If you start it from your pump you can go past the day 110 if you start it before day110.
But only if you initiate it from your pump, however that will be the last start you will get on it.
However your dexcom ap will not collect data after day110 and you will need to rely on your pump for the data during that session.
I did this a few times to build in a buffer for my new transmitter.
I get one every 90 days and I don’t want to be without one.