New Normal - Higher TDD = Shorter CGM Sensor Lifespan?


For the past month or two, Liam’s TDD has gone up from between 5 - 7 to between 10 - 14 TDD. I’m also noticing that, coincidentally perhaps?, we are not getting as long of a lifespan from each of his sensors. Now, logic tells me that these two things shouldn’t be related, but it’s just strangely coincidental that when he was doing 5 - 7 TDD / day we could get 2 weeks out of each sensor, but since his needs have gone up, he’s suddenly only getting between 7 and 9 days out of each sensor.

Does anyone have an explanation for why this could be? Or are these two things somehow possibly related?


Seems to me they couldn’t be related, but you may already have answered your own question. Did you start using a newer supply of sensors?

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Well, that was in November so it would make perfect sense that we’re now moving into the bad batches discussed here! Thanks for refreshing my memory on this!


You have some time yet, but my son is now using between 65-100 TDD. So it keeps getting worse. Hopefully my wife is able to work it out with the endo, whose current prescription keeps getting interpreted to = one box of pen vials or one vial per month. Really getting frustrated with the effort to get the correct amount of insulin prescribed.


I’m also one who uses 60-100 units a day lately, but I get a month out of each sensor (mind you putting up with a lot of jittery readings and lots of restarts and a couple days without data).

One thing I do notice is that the more up-and-down movement my BG has, especially rapid up-and-down movement (single or double arrows), the sooner my sensor dies. It was when I switched to eating low-carb that I was able to make the leap from sensors lasting 14-21 days on average to a month on average,a nd I think it was largely because of the more stable blood sugar. I’m eating more carbohydrates now, but I’ve continued to largely avoid foods I know make me spike (such as cereal) in an attempt to maintain as steady BG as possible, and I’ve managed to keep up the month per sensor for the most part, except for a couple that only last for 14 days.

So not entirely sure they are related, but for me, BG stability and sensor longetiity do seem to have a positive correlation.


the only way I would see them being related is tangentially – if simultaneously his blood sugar numbers became much higher and/or erratic. I’ve read that running higher and having more swings can sort of exhaust the sensor. But that’s the only way I could see them being related.


He has been eratic more over the past month or two as we try to figure out the new insulin requirements. It seems to be a constantly changing target for us right now.

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I can absolutely relate. Takes me probably 10 calls/emails and a couple trips to the pharmacy in person.

It’s got to be SO specifically written. And of course those words are an opaque mystery to the user/helper. Sigh.

And as far as the TDD goes, it’s very curious. EH isn’t willing to track sensor use stats as much as you guys are, but these new G6 sensors don’t last as long as prior sensors. @Jen are you getting the long wear out of the G6?

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My endo asks me how much I want her to prescribe Liam…I tell her as much as I can get. She currently prescribes him for 4x his required TDD amount. She’s never argued at all about his requirements or what she should prescribe for him. I tell her what I want, and she writes prescriptions.


Do you see a pediatric endocrinologist @ClaudnDaye ?


Ah, bummer. I was hoping I could switch. 4x the amount is awesome.

Sensors have an expiration date but not manufacture date. So, I use the expiration date to identify “batches” and timeframes. But more in terms of thoughts about when/how they were manufactured and nothing to do with a sensor actually “expiring”.

I found the sensors which had expiration date prior to April 2019 (or so) to be substantially better than the sensors which had expiration dates later than August 2019 (or so).

This is across multiple lots.

For us, it was a very noticeable change.

I don’t think it was an intentional and malicious change on the part of Dexcom, but regardless, I do firmly believe it WAS a change on the part of Dexcom in terms of the sensor. My opinion is it was an unintentional change. Still I have no doubt it WAS a change.


That is very interesting. For sure, as we have progressed into the world of puberty we have gone further into more peaks. Definitely worth considering further imho.

Here’s the stock I just started…I didn’t look at the previous box, but I think it was the same date since we usually get 3 boxes at a time, we have 2 with that date on them left, and they usually have the same date on them in the same box/package.

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I just happened to search to see if I had made any past posts on TDD (which I thought I had). Looks like, since 2019 when I made the original post, his TDD has gone up two-fold. He’s now averaging about 40 units per day. He isn’t listening to me!!! I’m asking him to STOP GROWING!! :smiley:

I started noticing because when I filled a POD with only 100u, his POD was running out of insulin before expiring. I have to fill with 150u now.


@ClaudnDaye Funny how kids tend to ignore that plea!! T1 or otherwise, the words go right over their heads!


He might be using close to what I am using now! :open_mouth:

I am not totally sure where to see it though. Like in Loop, if I touch the “Pod” icon, it shows a line that says “Insulin Delivered”, but I am not sure if that is a daily average or if that is a total for that pod or what that is. Not sure where TDD is.

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I pull the report from NS.