I have found that the sensors work fine as far as firing up (there is some controversy over the accuracy). I am currently 12 days into my "spike" test to see how much foods and exercise impact my sugars. The biggest issue I have had with Libres is knocking the sensors off. Here's a rather scummy looking concoction using my wifes physio tape:
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Although this looks terrible it is working for me on this occasion.
I tried waterproof island dressing. These look smart but when I sweated on workouts curled up
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It would be great if the Libre came with 2 options, the first would be a wider adhesive than the few millimetres at present (G6 like), maybe 1.5 centimetres, then a sports version perhaps 2 centimetres, being both waterproof and as sticky as the adhesive that hospitals use (I know it takes ages to get rid of the adhesive after use, but this is better than the frustration of loosing sensors a few days in, as I have done on many occasions with sports).