Dexcom G6 transmitter messages

I started the Dexcom G6 earlier this year and I’m nearing the end of my second transmitter, but I’m not sure what messages I should expect telling me when the transmitter will actually end.

For my first transmitter, I only had the CGM linked to my Tandem t:slim x2 pump. It seemed like the ‘transmitter ending’ messages were inaccurate - the transmitter ended 10 days before the pump said it would then and they don’t line up with the pump’s messages now.

For this transmitter, I’ve still got it linked to my pump, but I now also have the G6 app. I got messages in the app saying the transmitter had three weeks left, then two weeks left, but no message at one week. I’m ignoring the messages from the pump since they don’t line up with the app.

The official 3-month date for this transmitter finishing was 5 days ago, so it’s obviously lasted longer than expected. It sounds like transmitters can last 100-110 days.

Do you usually get a ‘this is your last session’ message in the app if you start the transmitter and sensors with a pump? I’m not sure if this transmitter still has another go in it for my next sensor in 5 days time or if I should start a new transmitter with the new sensor.

I’ve got another transmitter on hand, I’d just like to squeeze as much time out of this one as I can.


I may get that message, but I use xDrip on android, which shows current days. I think I get a warning when close, but I also mark my calendar on the day I start, and calculate 90 from that to mark when I should keep track each day. Sometimes get 95-105 days per xDrip stats.

Not sure about Tandem. But eventually you’ll get a this is the last transmitter session message when applying a new sensor. Then on the next sensor start it will prompt you to pair a new transmitter.

I find they last at least a couple of weeks longer than 90 days which is why after a couple of years I’m ahead one whole transmitter.


Hi, I don’t get those on my Dexcom?? I personally just try to get as much time out of everything I use. Can you plz tell me which

Hi how are you? I don’t get those messages from my Dexcom?? I try to get as much time I can out of everything as I can. I’m confused about your messages your getting.? Which set up do you use on your Tandem Tslim? My reason for asking is, I have a lot of extra Tslim devices that I’d like to donate to someone? Can you please let me know? If it’s what I have, I’ll give them to you. They are new and I’d love to help with them. Email me and we can discuss this?? Thx

The official Dexcom site gives “three months” as their transmitter life, but reddit, etc concurs that G6 transmitters have a 110 day life. G5 transmitters had 112 day life. A new sensor won’t let you start with a transmitter older than 100 days (you’ll have to pair a new one). (This is all automated into the system – if it lets you start a new session, it should work the full 10 days.)

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I just change mine when it shuts down. I don’t try to start it back up again, take it off and dispose of it properly. I can’t risk a sensor if it doesn’t connect to it

Thanks all.

I changed my sensor this morning and used the same transmitter. The transmitter hit 90 days on 9 Sept, so today is day 100.

A few minutes after activating the new sensor (at the start of the warm up period) I got a message on my pump saying ‘Low transmitter battery; Please replace your transmitter soon’. I left it as is to see what happened.

It went through the warm up period and the old transmitter with new sensor have been running for 7 hours now with no problems.

I’m curious if the transmitter will last the whole 10 days and if I’ll get a message in the app telling me anything about the battery.

So far, there haven’t been any messages about the transmitter’s battery in the app since the ‘your transmitter will expire in about 2 weeks’ warning. That was on 6 September, so it might end tomorrow, but I didn’t get a 1 week warning message, or a ‘this is your last session’ message in the app when I started this sensor.

It seems like the app messages might differ if you start sensors and transmitters with a Tandem pump instead of in the app. Or it’s possible they’re different because I’m in Germany.

If the transmitter ends in less than 10 days, I’ll end the sensor, pop out the transmitter, wait 20 minutes and start up the same sensor with a new transmitter.


The transmitters are authoritarian about this; they won’t start a new sensor if they have passed the Dexcom limit. IRC the Dexcom app (and BYODA) enforce this. You started the new sensor 99 days into the transmitter, though remember the transmitter counts seconds, not days, so the time depends on exactly when you started the original sensor.

It’s possible to reverse engineer the Dexcom calculation but the standard rule of thumb is that you can activate a new sensor up to (but therefore not including) 100 days.

The low battery is a warning you should consider. My own experience is that old transmitters are unreliable. Apps like xDrip+ will tell you the battery voltage (apparently in cV!) The “battery” is a single cell, its functional lifetime depends on manufacture date (before the transmitter manufacture :slight_smile: storage conditions, usage and the gods of chemistry. 10 days shouldn’t matter much if the previous 10 days, the previous sensor, were fine.

In fact the transmitters keep on going pretty much forever so long as they don’t have to do anything. I’m on the G7, 100 days in, and my old G6 transmitter is still registering on my 'phone bluetooth any time I get too close to it, like all those nine plaintive G7 transmitters.

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My understanding is Dexcom will not not let you start a new sensor if there is not at least 10 days left on the transmitter. I’ve never had a transmitter expire in the middle of a sensor session.


I get the same message @Josie gets, I recall getting one saying my transmitter would last one more session, but then that next session ended and it didn’t require a change until the the end of that session. Effectively it lasted one cycle longer than a precise 90 day period. Eventually I had an extra transmitter, just as @josie says…

Thank all.

This transmitter is currently on day 105 and I haven’t received any more messages about the transmitter on the app or in my pump.


The connection is cutting out a lot between my Tandem t:slim x2 (a few times a day for 20-30 minutes each time), but it still gives readings on my phone. I guess the pump receiver isn’t as strong as my phone’s receiver.

Even though I haven’t gotten any ‘last transmitter session’ or ‘lot transmitter battery’ messages, I’ll be changing my transmitter next session. The signal cutting out isn’t helping with looping and I’ve got a spare transmitter anyway, so I don’t need to push my luck.

A transmitter won’t think it has “expired” in the middle of a sensor session based on the date. But it can stop working in the middle of a sensor session, based on the fact that it was too old and actually did expire. :joy:

I’ve experienced that a few times where it says “this will be the last session for this transmitter”, but it doesn’t actually make it the entire 10 days. It just flakes out.

If you are getting flaky readings or connections, and you have a bit of spare time, it’s worth it to call Dexcom customer service. They can do a remote diagnostic run on your transmitter and if it is failing within your warrantied battery life, they will replace it. This has happened to me a couple of times (granted, when I had a run of a few mysterious sensor failures), but I believe it’s fair to keep Dexcom aware and accountable to its transmitter issues, even toward the end of their life.

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Thanks. This transmitter is past its 90-day lifespan already (today is day 105), but I called them about an issue with my previous transmitter, so I’ve already got a spare.

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To update: My sensor expired today. I was planning to swap the transmitter out today anyway since the signal has better cutting out often.

I ended the session (both sensor and transmitter) on my pump and shortly after, the app prompted me to pair a new transmitter.

There were no time-specific messages like a ‘this is your last session’ message in the app, or any other warning since the ‘2 weeks left’ message I got last month. Just ‘low transmitter battery’ 20 days ago, and then the ‘pair a new transmitter’ message after ending the session today.

The transmitter lasted 20 days over the expected lifespan, so 110 days in total.