Hello
@digihat,
When I used Libre 2 it took me a long time to conclude that my body and Libre 2 were incompatible. Sometimes my sensor could start high and stay high all 14 days, or start low and stay low. But sometimes the sensor could start high and end up low, or vice versa. If the actual to interstitial difference was within 2 mmol/L, I 'd tolerate that because my trend arrows and trend interpretation from the graphs was for me the most important thing I needed to know - ONCE I knew I was somewhere in range (4-10). So I used my Libre most of the time, but took fps at least 5x daily, sometimes 7 or 8. More when I was on a long drive or I had no sensors left and was waiting for replacements.
When the differential got above 3 mmol/L, I routinely asked Abbott for replacements. I had over 50% failure rate, either from a sensor just literally stopping before the 14 days or becoming unworkable with the differential. Abbott replaced every failed sensor. I frequently ended up telling the Abbott representative that in the final analysis the failed or failing sensor was blatantly "not fit for purpose" which always brought the correct outcome.
In spring 2022 the NICE Guidelines for T1 and CGM were softened to improve availability for all T1s AND to increase the range of the lower cost CGMs that were to become available. I moved to Dexcom One and my failure rate reduced; but this was still not perfect or even very close.
Earlier last year ('23) I self-funded Dexcom G7 which has proved to be invaluable: excellent sensor reliability and sensor readings are very close to actual. This proved to me that there was a CGM that could work well on my body and I asked my Consultant to upgrade me to G7. This, most thankfully, was aporoved later in '23 and G7 hardware has continued to serve me well; the app on my android 14 phone has crashed 5 times which is a bore since it freezes you out completely and only a factory reset can unfreeze my phone. After the 1st crash Dexcom provided me with a Receiver (the equivalent of a Libre Reader).
My conclusions from this are that:
There is a CGM that is compatible with me. I accept that many others get a decent level of compatibility with Libre 2, but I didn't.
The reduction in stress in having that reliable compatibility can not be overemphasised. Knowing that the screen is displaying data very close to actual is extraordinarily reassuring. Not having to fp before every bolus circumstance, because the reading is right, is a big part of that stress reduction. The stress from the hassle of having to seek replacements for 50% of all sensors was in itself a burden.
This long answer to your question "how long before changing a sensor" is still muddy. I sometimes stuck with quite large disparities because I'd got used to those, could work around those with mental adjustments AND because at that time there was only one low-cost option: Libre 2. The 3 higher cost alternatives of Libre 3, Dexcom G6 and G7 were simply not in the vocabulary for my support. Now there are better lower cost options. Also I demonstrated that:
I'd really tried to make L2 work.
I had the evidence (Abbott invoices) proving how frequently Abbott had replaced sensors.
I'd found and self-funded an option that did work and shared that proof with my Consultant.
I now am genuinely making a big saving on greatly reduced fps and thus reduced test strips. These come from my GP's prescription allocations; my G7 comes from the Hospital's budget allocations - but no-one seems to make that an issue (so far).
My Consultant was wholly on-side with the principle that my stress reduction was a great improvement for me.
Hope that is if some help.
