Dexcom: another DOA transmitter

It is the third time in a year and a half that our second transmitter in a 2-transmitter shipment fails, leaving us without a working one.

Dexcom tells me that transmitter failures are rare.

I would willingly order an extra transmitter to always have a spare. But their shelf life is VERY short. We received the DOA one in mid April and its best date of first use is in October. I called Dexcom about it, and they confirmed to me that this is a normal interval. Short shelf life.

I’m troubled about that shelf life info, as I’m holding an unused one in reserve now that I’ve switched over to Guardian 3s for the 670G. I assumed it was ok indefinitely. Really curious what could be driving the limitation since you’re not running the battery until you initialize the thing.

Speaking of battery: I installed the xDrip app in order to keep my last Dexcom transmitter running well past the “dead battery” shut down, because I was about to start the 670 in a couple of weeks and didn’t want to be CGM-deprived OR have to use my held-in-reserve G5 transmitter. Have you looked into that? There’s an IOS version now as well as Android.

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If you use for more than the prescribed 7 days won’t your supply quickly outpace your demand?— oh, no that’s the transmitter not the sensor, nm

With the G4, there was supposedly a little magnet in the packaging which would trigger a micro-switch in the G4 to power it up when the transmitter was removed from the packaging. Hence the warning to not remove the G4 just to look at it but rather wait until you are really ready to use it.

This is apparently different for the G5. The G5 transmitter would appear to be already powered on when it leaves the factory although in very low power mode and waiting for a BLE pairing request.

Between the G4 and G5, it would appear the G5 has a larger power drain then the G4 while sitting on the shelf. Still a small power drain but likely enough to make a difference in G4 vs G5 shelf life.

BTW - @Michel - What do you mean by “best date of first use”. Are you referring to the “SB” date on the G5 packaging or is this a different date you mention?

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Well damn. I never encountered this info; I just assumed it was like the G4: not turned on until you pull it from the box. Grr. BUT it remains true that that hard “Out of power” hard line is not in fact a hard line. The Dexcom software won’t let you around it, but xDrip doesn’t have that limit coded in and lets you keep on receiving as long as the transmitter actually has power. The developer told me he’s gotten as much as six months out of a single G5 transmitter. We leave it to others to speculate as to why the limit is hardwired in then…

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Interesting, we have not had this problem, although we are only on our third transmitter. Interestingly, a friend who was mistakenly shipped a G5 transmitter gave us a very expired one and it worked perfectly.

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How does the box prevent the xmitter from being activated? I noticed a message in my xmitter box that said not to remove it until I’m ready to use it. I see no magnet or other obvious item inside the box.

Don’t have one in front of me but I recall noticing that the bottom of the recess in the plastic tray that the transmitter is nestled in was thicker, as if there were some kind of passive de-activator embedded there. Must be something like that. ¯_(ツ)_/¯

@Dave - Per my understanding the box no longer keeps the transmitter in a powered off state and the notice you refer to is is just a holder over (for whatever reason) from the G4 transmitters but actually no longer relevant from a functional point of view.

@drbbennett - Try ripping apart the G5 box where you see the thicker area and suspect something might be in there. Certainly if you find any device (or magnet) in the G5 box, that would entirely change my thinking.

I know some people are still on the G4. Perhaps one of them could rip apart the box and confirm that the G4 packaging does indeed contain a small magnet (or similar device)?

I have looked in my G5 boxes and found nothing. I no longer have any G4 boxes to look at.

Seeing is believing.

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I still have the box. The xmitter sits in an extruded plastic tray that when examined with a light shining through it, shows nothing inside of it. Also, I shined a light through the thick foam top piece, and it too, reveals nothing upon visual inspection. Maybe something presses against a tiny switch??? I can’t check the underside of the xmitter now, as it’s attached to me.

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Definitely not. I have seen the inside of the G5 via Dremel. It would be hard to imagine a pressure switch in there somewhere. The G4 was reported to have a magnetically operated micro-switch and presumable it would be possible for the G5 to have this also. Although my understanding is this is not the case any longer.

Note that with the G5 vs Dremel - the Dremel definitely won. The G5 was in very sad shape afterwards. But certainly interesting.


Quite the puzzler–I just took a small magnet and slowly and repeatedly passed it all around both the tray and the foam cover piece. No reaction whatsoever. It must be voodoo.

My wife said maybe they just don’t want patients to lose the thing. It’s so small, it would be so easy to misplace, if removed from the package.


As you said, then: must be that it’s just using a minimal amount of power while the BlueTooth set-up process hasn’t yet been initiated. Could be a software switch, or it could be that it just doesn’t draw that much power until it’s actually paired and sending data. Wonder how they account for the fact that these things could be sitting on the shelf in the warehouse for an indeterminate period before they’re shipped. Miracle of just-in-time manufacturing maybe…?

If it was broadcasting at all wouldn’t your iPhone detect them automatically? I too have scoured the packaging to look for any sort of switch mechanism after tech support told me they turn on when removed from the packaging (I have a G5-- I suppose that phrase could have been left over from G4).

The G5 transmitter box has an SB date. This is the “Ship by Date”. It is never a problem when shipped direct from Dexcom. But when buying through a distributor, you should always check this date when you receive the transmitter. If you get one that is past this date particular if more than 30 days past this date, I would absolutely call and request one not so old.

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I had one transmitter give a low battery warning and then died abruptly leaving us without a backup. After some consideration, we pulled out our year old G4 transmitter and worked perfectly. It is unfortunate that the battery is so much worse in the G5…

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My SB date is 2018-02-19, so guess that’s pretty fresh (glad I kept the packaging).

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How the G5 activates its battery:

  • the battery of the G5 activates when you bed the G5 transmitter into a sensor pod. There is no magnet in the packaging.

How the G4 activates its battery:

  • The G4 transmitter battery activates when you remove the transmitter from the packaging, because of the magnet/microswitch.

On the G5, the Dexcom warranty is good for 3 months after you activate the transmitter, even if it is activated way past the SB date. On the other hand, once you activate it (i.e. once you have embedded it into a sensor, even if you did not pair it), it is only good for 3 months from that date.

I should probably make a wiki out of that.


@Thomas, yes: I meant the SB date.

SB Date = Sell By Date.

Underneath the SB date, you can see another date preceded by a little factory icon: it is the manufactured date of the transmitter. Between the two, right now Dexcom lists 8 months, because, even in inactive state, the battery is losing some charge.

Dexcom considers that the “good” shelf life of a G5 transmitter is 5 months after it has been SHIPPED. They appear to keep track of the ship date on their database, even if a transmitter was sold by a vendor (but I am not 100% certain of that, I am inferring from what I was told). However, they will still warranty it for 3 months after it has been activated (i.e. bed it into a sensor), even if the activation date is past the SB date.

Dexcom specs the transmitters so that, if you activate the transmitters on the SB date, or 5 months after the shipped date, it still is good (per the spec) for at least 3 months of use.