My c peptide wasn't that far out of normal range when I was diagnosed t1. First clues for my case being t1 were a combination of all of this:
- Stupid high blood sugars (like up around 43)
- diet/weight history
- metformin + gliclazide did nothing for me.
That was all just speculation until the antibody test came back positive, which took over a week (was in hospital already when it all happened, so they had plenty of chance to test different things and get daily blood tests while waiting).
If you're antibody negative - it might be that you won't know for certain any time soon - unfortunately. In the mean time, best to act like you have type 2 just in case there's a chance of avoiding insulin etc.