It doesn't hurt to apply the sensor, or remove it. The 'needle' is a flexible filament which I don't have to have anything to do with, as it's contained inside a big plastic applicator. Once applied, I cover it with a 'cuff' which I bought online. The cuff isn't waterproof, but it holds the sensor in place a bit more securely, which means that the sensor is less likely to be knocked off my arm. This has happened a few times, in fact it happened just now! Luckily, I am about one and a half days away from its finishing anyway, so no big deal: I just applied a new one. I am grateful to be eligible for Libre on prescription. It is helping me to better manage my blood sugar, though, personally, I was not great at interpreting the patterns and adjusting doses as there are so many variables. However, by dint of constant practice, I am improving my blood sugar profile. It's true that you don't get much time to input data to the Libre reader so I keep a paper record as well, (Shock horror! - but I just paddle my own canoe), on a Desang blood sugar diary.