Mr Orange was tested last year, during a fairly severe cold he had (did you know cat colds can last 4 weeks?).
Was negative at that time.
He had a brother (Nougat) that died of diabetes about 2.5 years ago, so there is a family history.
Knowing what I know now, we'd have simply brought him home rather than putting him down or having him put in an oxygen tent and rushed to an emergency vet (from the emergency overnight vet we took him to), which were the only two options we were given.
Cats can actually be in remission from diabetes. Buff (Nougat's nickname) was quite a punk, though and my have been difficult to medicate.
Mr Orange is almost the exact opposite "personality"-wise.