Failed Sensor Characteristics
I have been using Dexcom G7 10 day sensors for a little over 8 months and while many sensors have been solid, there are some sensors that just aren't that great or tend to fail early. I am a scientific person so I have taken notes and noticed a trend with sensors that tend to fail. For the sensors that fail I notice the following characteristics:
- Brief Sensor Issues - For sensors that tend to fail Brief Sensor Issues tend to crop up relatively early in the sensor life, like day 1 or 2. These initial Brief Sensor Issues tend to be brief and may only show up once or twice. However, they will become more frequent and last longer. By day 8 they may last a few hours with more and longer drop outs. So you may see a graph like this with a lot of dropouts:
When this happens it is a good idea to get your replacement ready as the sensor tends to fail at night with unusually low readings and complete drop outs. Later that night this is what happened:
- “Drifting” time - When inserting a sensor I take note of how many seconds past the minute that readings tend to come in. For sensors that fail this time tends to drift 20 to 30 seconds or more past this initial time when the first readings come in. When a sensor is solid for all 10 days this drift is only 5 or 10 seconds at most. I admit this is a bit in the weeds, but for the sensors that fail they almost always drift away from the initial reading time a noticeable period of time.
- “Drifting” readings - For sensors that tend to fail the sensor tends to drift from calibration easier and tend to drift farther away from a finger stick. I also note that for a failing sensor this drift tends to be down from a finger stick, while a good sensor will stay close to or drift a few points higher from a finger stick. Calibration seems to do no good, even if you notice the drift.
- Connectivity Issues - Sensors that tend to fail will tend to not be able to send their signal very far. For example, if you walk out of the room without your phone or receiver you can go farther and still get a reading from a good sensor, while a sensor that will fail early will have a shorter range where this connectivity fails.
Overall I notice that bad sensors will tend to have more than one of these issues and the more of these issues I experience, the higher likelihood that the sensor doesn’t make it all 10 days. I haven't had the opportunity to break into my 15 day sensors yet, so I don't have notes on those sensors yet. I also know that each person is different, so you may or may not have these same experiences.