FUDiabetes

Dexcom G6 repeated sensor error

Hi! My mom is type 1 and has been experiencing repeated sensor errors. Today the sensor kept losing signal and we changed it tonight and then it came up as “no restart allowed”. It’s a brand new sensor! So frustrating. Dexcom will replace it but it seems like lately every sensor is bad. Can the summer heat affect how well it works?

She does not have a phone so she uses the receiver and I’m not sure how long those are meant to last. She’s had the cgm since last November.

Any thoughts or help is appreciated!

Thank you!

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One way to get around this error, after you see it, is to start a new sensor with no code, stop it after 15 minutes, and then start a new sensor again (with or without code, whichever you were planning to do). This is the technique I use to restart my sensors, but of course it also works for ones the G6 is falsely accusing you of restarting.

These false accusations can be frustrating, I think it throws the error if you start a new sensor quickly after stopping the last one but I’m not sure why they didn’t account for the fact that people want the data continuously!

I do know that the G6 user manual wants the sensors stored within a specific range of temperatures: “You can store your sensors at room temperature or in your refrigerator – as long as it’s between 36°F and 86°F”

So if the temps in where the sensors are being stored is exceeding 86 frequently it may be affecting them. I wouldn’t rule out summer heat affecting how the one currently applied fares either

I would expect it to last longer than that, though I haven’t used the G6 receiver personally (I use the app and the t:slim as receivers). If the majority of the errors are specifically due to lost signal I would be more skeptical of the transmitter personally but I wouldn’t rule out the receiver

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Agreed.
We set a 10 minute timer on our phone when hitting stopping the sensor and will not start the new session until the 10 minute timer expires.

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Ah thank you! We did do it quick! I’ll make sure to wait longer next time!

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Thank you! Yeah maybe working in the yard in the heat is throwing it off. Perhaps we’ll have to put an ice pack or something on it if she’s out there longer just keep it cooler.

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Normally signal loss will recover fine, but if it keeps happening there is probably some factor causing it. I’ve seen two main possibilities:

  1. Obstructions. The signal doesn’t travel very well through our bodies so if the receiver doesn’t have a clear line of sight to the sensor (clothes are ok) it’s more likely to drop the connection. I’ve seen this issue reported and experienced it myself at night; my receiver (it is a phone) is on the nightstand and the sensor seems to be prone to drop out if if I face away from it.

  2. Interference. The signal uses the same radio frequencies as everyone else’s bluetooth stuff, so if there are a lot of dudes around with bluetooth headsets etc the G6 signal tends to drop. I’ve experienced this in air travel; I couldn’t get a reading until the flight landed, and on ski slopes (seriously!) Other people have hypothesized about interference from WiFi systems in the home.

  3. Batteries. When the batteries get low the signal gets weaker. I suspect the main draw on the sensor (technically transmitter) battery is generating the signal. The DexCOM receiver doesn’t tell you the battery voltage (though it knows it) so diagnosing this is difficult. Check the expiration date on the transmitter (assuming you still have the package; not the date on the sensor box, the smaller transmitter box), if it is close I believe that makes it more likely that there is a depleted battery. It is possible that a receiver with a low battery might have the same problem, that seems less likely to me, but see below.

It can probably make the transmitter/sensor battery lose capacity more rapidly. Lithium ion batteries, the sort used in phones, are apparently fairly heat sensitive but the transmitter battery is a different sort of lithium battery. Round here summer peaks at about 115F outside but our house is typically under 86F (not always). I haven’t observed any battery, or other, problems from exposing a sensor I’m wearing to full sun and air temperatures over 100F (103F max in the last 30 days).

Electronic systems are normally OK up to around 80C (176F); my computer temperature limits at 84C and cellphones are typically running well over 100F so I wouldn’t expect a problem. However there was a report, recently, of a potentially faulty transmitter; changing the sensor didn’t help. If the transmitter starts failing within its 90 day life then that’s pretty much indistinguishable from a sensor failure (at least with the DexCOM receiver.)

They are mean to last “for ever”; well, as long as a cellphone lasts since they are broadly the same piece of electronics. The most likely thing to fail is the battery (just like a cellphone), but I would expect a battery problem just to mean that the receiver won’t show anything. You could try charging the battery just to make sure; it’s said to be better to let the battery discharge mostly (Microsoft says to something like 33% of capacity) before a recharge but if you are having problems it is probably better to put the receiver on charge just to make sure.

Same as me (well, October.)

So she should be on her third transmitter and it is just about to expire, or she has just swapped to a new transmitter and there is something suspicious about it. There was one other report here, recently, about an apparently flaky transmitter so if it is a new transmitter I would go back and check the box for the expiration date and/or see if DexCOM will send you a new one. (I believe the are pretty cheap for DexCOM so in principle that shouldn’t be a problem.)

Since you are using the DexCOM receiver the transmitters are the weak link; they tune out after 90 days, insurance companies typically resist giving you one more than every 90 days and DexCOM doesn’t seem to be set up to just replace them in the hope that this will fix the problem.

The problem is that unless you are seeing consistent identical sensor issues it is still more likely to be a combination of things; signal dropouts, environmental conditions (sensor site, temperature, activity level), failure to recharge the receiver in time… I suspect most DexCOM users just end up with an approach that “just works”; I couldn’t get the G4 to work but the G6 works and I’ve seen this with computers enough before to know that it works because the user adapts to it rather than the computer getting better.

John Bowler

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@jbowler that is an amazing write up. Thank you so much for your logical and clearly described experiences. I know that will help a lot of Dexcom users sort things out.

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Dehydration can also contribute to issues with sensors and BG readings. She should stay hydrated.

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