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