Do G6 firefly transmitters expire in exactly 90 days?

I am a CGM newbie - still on my first transmitter - and have a techie question about the G6 transmitter which is supposed to be replaced at 90 days.

If I start a new sensor at day 88 on the transmitter, will everything shut down exactly at day 90? And thus I only got 2 days on that otherwise new sensor? Or can I likely get 98 days on that transmitter?

If it matters this is the new “G6 Firefly” 8Gxxxx transmitter.

Official dexcom answer

https://provider.dexcom.com/education-research/cgm-education-use/videos/how-replace-your-dexcom-g6-transmitter

Dexcom says this
The transmitter battery is good for up to 3 months.

But what it means is that days are counted from when you start transmitter, and force end at 90 days, even if battery still has power.

If you use dexcom phone app or dexcom receiver, answer is up to 90 days. App or receiver shows day count.

But transmitter is slowly draining power before use, either before shipment, or by user still using prior transmitter. So may not get full 90 days if battery/signal is too low before 90 days of use.

“If I start a new sensor at day 88 on the transmitter, will everything shut down exactly at day 90? And thus I only got 2 days on that otherwise new sensor? Or can I likely get 98 days on that transmitter?”
Would likely get error message and would prevent start of new sensor when less than 10 days left on transmitter day count.

Whole different story if using xDrip or Spike. But with firefly, I think still unknown if dexcom has hard stop when transmitter days get to 90. With older 80 transmitter + xDrip, definitely get more.

I thought the transmitter’s programmed death date is 110 days after activation?

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Oops, I agree, not 90. I have seen 112 reported.

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The transmitter prevents you from starting a new session with a new sensor if the death date is within a week

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I don’t have any Dexcom documentation to show it, but the 110 day ballpark makes more sense. That way it’ll be good for at least 9 10-day sensors plus a little margin. I did appreciate that video you linked to where it says there is a days remaining countdown at the end of the transmitters life, and it won’t let me start a new sensor if less than 10 days was left on the transmitter.

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I also was afraid that the transmitter could expire before the sensor reached day 10. This fear seems to be unwarranted. Dexcom only lets you start a sensor if the transmitter has at least 10 days left. No need to count days.

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Has anyone thought about restarting the new sensor only 2 days in? Instead of waiting until day 9/10? Maybe this would get around some of the built in logic?

The latest transmitter (serial 8Gxxxxx, Firefly) has new logic to expect sensor differences during first day or so after insertion. Folks are still trying to figure out how/if restarts or extended use can be done, and if accuracy is impacted.

That is really awful because I soak my G5’s for a day to get excellent results on the first day that I run a sensor live. I’d want to do the same thing with a G6 but it sounds like Dexcom is going to force me to have a lousy first-day experience with them. Why do they have to ruin things?

The answer to that is pretty short: Money

It was a rhetorical question, but you are correct. :slight_smile: