Not sure what you mean with
furry tongue, so do forgive me if I botch this, being Dutch and all, and a T2. If it was diagnosed as
hair tongue, it'd usually be brown or black... When you say it was cream coloured and there was a clear connection to high blood sugars, I'm thinking more along the lines of thrush... And that is a known, regular occurrence with high blood sugars, (in the mouth and private parts, usually).
Just a T2 though, but my oral thrush was, when it occurred, cream/yellowy, and this rang a bell. There's a gooey gel for that that might help too, should blood sugars be unmanageable for a bit due to a virus or something.
Dunno if this helps any, but just thought my 2 cents might be of use. And if not, no harm done.
Jo