Just my experience, but: I wear Freestyle Libre (only sensor supported by my insurance). The sensors are almost always off or pretty off - but I believe my body is at least partly to blame. Ever since I caught on to this, I always test with both sensor and one or both meter(s) (Freestyle Light and Contour Next). The meters always agree. The sensor can be way off, might be higher than the others at in the first 24 hours or so, but always is lower than the others within 3-5 days, and if I leave it on (because insurance won’t pay for extra) it’ll usually be testing at about 40-64 on the 14th day regardless of my actually bloodsugar. The farthest off I ever saw it, a sensor said 64 and my BG was over 200. I mean, DREADFULLY off. Rarely, I get a sensor that might be sort of somewhat close to normal for the duration, but that’s not as common.
The sensor, though, gives me what the meters don’t: a knowledge of whether my BG is going up or down, and how fast. I find that invaluable.
However. Like my mother, I have a tendency to form excessive scar tissue. A lot of it. (Her appendectomy scar started at I think she said about 4" long when she was 10, and was a good 15" long by the time she died at 80 - and she claimed it was still growing.) Unlike her, I figured out that for me eating dairy and gluten was exacerbating it. I scar a lot less excessively now than I used to. But I think my body is still trying to gather plug up canulas at a stupidly fast pace. Mom was a lifelong dairy addict, and had trouble with all of her surgeries late in life because of crazy scarring (augh, the colostomy bag); I want to avoid that. It’s also not uncommon for my Omnipod pods to not last 3 days before it seems like I’m not getting all the insulin they’re trying to deliver, although I can’t figure out where the insulin would be going instead. I should draw out what insulin is left in such a pod, one of these days, to see how different the amount is from what the PDM said before I stopped it.
This current sensor is unusual even for me. Usually the first 24-36 hours, a sensor can read a little higher than the meters. This one was about 25% low from the outset. The meters agree with each other (I actually also have 2 old Freestyle meters that I thought I lost, so there are 4 meters), it’s clearly the sensor that is in the minority.
Anyway. Just a data point. My joints and tendons and at least one organ are all full of cysts and scar tissue, it’s not like canulas and syringes are the only problems.
So if you’re diagnosing a meter-sensor discrepancy, think outside the box.