A couple of years before being diagnosed, I felt thirsty quite a lot, for no logical reason. I worried that I was perhaps diabetic but did nothing about it. I had a medical, as I was going to become a teacher, and was surprised and delighted that my urine test was normal.
18 months to 2 years later, the thirst had become unquenchable and I was diagnosed Type 1. Years later I asked my consultant if it was possible that I had been in the process of becoming diabetic, even though my urine had tested negative for sugar. He said it was possible. I can't remember his explanation but it was something about the way the pancreas can recover for varying periods of time, before it gives up altogether.