Oldest G6 trans to start new sensor?

Does anyone know the age of a G6 transmitter on the last day it will start a new sensor? I think it is around 100 or so days, but does anyone know the exact last day?

I’m changing to a new insurance provider, and my current G6 transmitter is almost expired. I would prefer to wait to replace transmitter when I am on new plan (Sept 1) but want to figure out whether I will be without cgm if I do that. Thanks!

@Jag1, the app displays 2 kinds of warnings. I think one is 2 sessions out and says “time to order”. The other says “this will be your last session”. I didn’t pay attention to the exact number of days.

Yes, that’s correct, it’s the last day when that second warning is given that I need to know. Embarrassing to admit, but I haven’t paid attention either, though I’ve been using a G6 almost since they were first on the market. Hopefully someone else has paid closer attention.

You cannot start a new sensor after day 99 is done. If you are just 1 minute into day 100 you cannot start a new sensor.

It may make economic sense to “stop” the old sensor on day 99 (giving up a day early) just so you can get 109 days on your current transmitter.


There is not a specific day because it depends on the schedule of your sensor changes. That can be affected by sensor failures or changing sensors early. For sure the hard shutoff is 110 days.

Supposedly the G6 phone app will not start a new sensor if you are unable to get 10 days. But I use a Tandem pump and have occasionally started a sensor on the pump and then immediately get a transmitter failure alarm.

I am lucky to have some extra transmitters so I usually do one more sensor session after my 90 days and that gets me to 100 days. But chances are I could get one more session.


What @Tim12 said…if you have spare sensors but are trying to get every last day out of the transmitter. It might make sense to plan ahead so you are starting a new sensor on day 99. Then you can have some confidence that the sensor and transmitter will make it 10 more days to day 109.


I change my sensors every 10 days but really it’s just a smidgen over 10 days (it takes 10 minutes or more to peel off the old sensor, clean up the transmitter, and put it in the new sensor.)

As a result it is say 10.01 days per sensor, or 10 sensors gets me to day 100.1, and I don’t usually get the 11th sensor.

One exception… I had a sensor tear (the cloth adhesive part was still mostly attached but the sensor plastic/rubber part had ripped off and the wire was pulling out) and fail at day 8 or so. As a result I got about 108 days (11 sensors) on that transmitter.

If you do the CSV spreadsheet export from Clarity, one of the columns is “Transmitter Time (Long Integer)” which is number of seconds since the transmitter started. 100 days = 8640000 seconds, 110 days = 9504000 seconds. I always get above 8640000 seconds before I have to switch to new transmitter.

I have good insurance coverage and get a new set of 9 sensors and 1 transmitter every 85 days or so. Because I usually get 10 sensors per transmitter I actually have a couple extra transmitters at this point. At this point on I’ve been on the G6 for 3 years so over 100 sensors. I’ve been really lucky with sensors - I had two that never worked (real bleeders) and that one that ripped. I had one transmitter fail about day 60 during a change, when the plastic of the transmitter actually broke as I was removing it. Dexcom sent me replacements for all the above so I have a couple months stockpile of sensors and at least two extra transmitters at this point.

By the way I use the Dexcom receiver, not my cellphone or a pump. The logic on transmitter change may be different with the cellphone app or pump logic from the way folks describe it.


Thanks, great info, that’s just what I need to know. Ironically, my 99th day with my transmitter is Aug 31, the day before I start on my new health plan. I’ll be on Medicare for the first time on Sept. 1, but think I’ve gotten everything lined up. A&B, B-Medigap, D, and dental all starting on the same day.

Only possible issue is that being on Medicare, I need to get my Dexcom stuff shipped from a DME, which is a change since I’ve always gotten from a local pharmacy prior to this. I’ve lined up a DME also, went with Edwards, and given them all my info. So I guess this will be a good test of whether Edwards is up to the challenge - they’ll have 9 days from Sept 1 to deliver my starter kit. (BTW, I told them I already had a receiver so please don’t send one, but they told me they need to send me a receiver in order for Medicare to pay. So I guess I’ll have two receivers that I never use instead of just one).

I use xdrip with my Android phone and watch, so Clarity is not possible for me - I use tidepool instead and don’t think there is any transmitter start info on there. Not really sure what time I will cross over from 99 to 100 days, but I’ll watch it for the next couple days.

Of course, I could just pay the extra $150 to get a transmitter on my current plan and have an extra transmitter for the future, but this sounds like more fun.

I’ve learned from the school of hard knocks the very very worst day to start a new health plan is Jan 1 because that’s when everyone else in the world is switching over AND it’s also when the paperwork folks at insurance, pharmacy, and docs offices are on vacation, and (repeat) preapproval for CGM and other tech is sure to stall out. I’m hoping a September 1 switchover will be much smoother for you!

I’m very impressed that your folks at Edwards already seem to be lining many paperwork details up in advance.

It wouldn’t surprise me if the “transmitter time” column was somewhere in the Tidepool export but I’ve never found it yet.

Other than the disadvantage of possible higher costs due to having to meet deductible again.

When I switch to Medicare, will have similar situation, and will try to postpone some costs to first Medicare month when possible.

110 days is the max, but the battery does lose charge over time. I ordered one transmitter too far ahead of time. As a result it only lasted 90-100 days.

Ordering a transmitter a week and half ahead of time seems a bit risky.

Yes, since I need to meet deductible anyway, and since I am paying more on the current health plan than I will be after deductible met, made sense to move as much as possible into the short year from Sept-Dec.

I started new sensor on Aug 31, on 99th day. Started correctly, and running fine. Actually running better than my last sensor so I wasn’t sorry to see that one go a day early. (My experience - some sensors just more accurate than others - this one hasn’t required any calibrations and numbers are right on.)

I am VERY impressed by Edwards so far. Would recommend them to anyone starting with a DME. So far no complaints at all. I have a direct contact there who got the info from doctor and new insurance before it was even active yet, and let me know when anything was needed. Talked to her today (Sep 1) and all she needed before shipping was for me to pay the deductible, and she sent me receipt with shipment today. So hopefully it looks like I will be in my 10 day window with time to spare (fingers crossed).

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So my new transmitter, 10 sensors, and (unneeded) receiver arrived today, on transmitter day 103, six days left on my sensor. Worked out great! Thanks for the help, and further kudos to Edwards for DME support.

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Just for future reference.

I prefer easy. And since I restart my sensors, I am always using my transmitter past 100 days. I don’t pay attention to what date it will end, I just keep using it until it won’t let me use it anymore. That’s somewhere between the 100-110 days. But to get the full benefits of it you’d have to keep track of how many days you are into it so you can start or restart a sensor in time.

But there is an expiration date on the transmitter box. It is usually many months out when you get it, 5-12 months away. The battery is only good for so long. They work past that expiration date and depending on each transmitter it will vary…but it’s around about 1-2 months past it.

I know because at the beginning I secured an extra transmitter as a back up. Then I had a couple of failures before 90 days, and when I switched to Medicare I got sent one earlier than I needed. Eventually I ended up with 4 extra transmitters sitting there and 3 of them ending within a few months of each other. So I used them until they failed. They worked, but somewhere at the end of their life they start losing their signal. So it worked to use them past their expiration dates, although not to the full 90 days. I ended up with 2 back ups with better dates now. Although right now I am using one that expired 2 months ago and it’s going strong. But you do want to keep track if you have a backup or two of the expiration dates on the box. They don’t always send them to you with dates that far away. If you get one with a 5-6 month expiration date away, it’s fine if you are using it right away, but if not… they do have a lifespan.

I don’t pay for my transmitters or sensors. I love restarted sensors the best, they are less work on accuracy. And I just really like easy.

I have always done the same, re-using transmitters until they won’t start, and never paid attention either. But if I had done that this time, I would have run out and had no transmitter and no CGM for several days. Which is why I was glad that @Tim12 HAS kept track of it and let me know the last day I could start my transmitter (99 days). If I had had a spare transmitter then I would have used it, but I do NOT have a spare transmitter so my transmitters are always new with brand new batteries.

I used to re-start sensors also, but they are never as accurate in my experience. They ALWAYS start off about 40 points too high, and REQUIRE calibration to get even close to correct value. And a single calibration is not adequate, they need calibration with a high and low number as well. And finally, even once you do get them properly calibrated, the response curve does not match that of a new sensor, so they go out of calibration in several days and need to be re-calibrated before the 10 day restart is up.

A new sensor will sometimes start reporting a bit lower than actual BG, but never off as far as a restarted sensor. And more importantly, I have found that if you give it some time it will usually close in on a value that is close to accurate - if not I will sometimes calibrate, but I prefer to wait it out for a day or so to see if it corrects itself. If you have no choice you can get extra time out of a restarted sensor - but it is not as good as a new sensor in my experience.

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@Jag1 Yes, it’s good he had the dates for you. I can never remember if it’s at 99 or 100 days. I’ve not had to worry about it since I always have a backup supplies.

How different we all can be. Brand new sensors for me end up being off by a lot. On me they can go off by 80 points within the first 1-12 hours. Usually I am calibrating it either right when it starts or a couple of hours later. If I am starting it before bedtime I shut off my receiver and phone and don’t calibrate it until the next morning. But I woke up once and forgot it was a new sensor and it said I was at 185, 12 hours after it was started, So I dosed, and then remembered it was a brand new sensor, so I did a finger stick and I was at 105. Then I had to eat.

I really like mine to be within 5 points of my meter. A new sensor takes quite a few calibrations the first couple of days to refine it. A restarted sensor is just 1-3 calibrations the first 24 hours.

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Marie, your experience matches my experience with sensors too. Since I started using the front or sides of my arms, my sensors have been spot on. I still check them with a finger stick and am amazed that the result is always within 5 points. Even the first day with a new sensor is spot on. I never use the code since I finger stick anyway at least morning and night. I also soak the new sensor about 10-12 hrs. I use to always used my abdomen. I feel like a new woman!


I’m so happy to read this, seeing how much you’ve struggled with Dex in the past!


Thanks Robyn! I might have to try the back of my arms and see if I can still sleep with sensors there. Like you, I am 5ft tall and I am running out of space on the front of my arms. I put on a new sensor this morning and it started working perfectly from the start. I am amazed!


When you say the front of your arms, do you mean your bicep. I’m afraid of hitting muscle because there is no fat there.

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