Thanks for the replies. We tested every 15 to 30 minutes, and after getting him up to 158 and then seeing a steady drop, we decided to take him to the Emergency Clinic. The doctor there agrees that this might only be a reaction to the urinary infection, and not a return to diabetes. He'll be in good hands unil he is stabalized, which means 24 hour on-duty doctors and hospital care. If all goes well and he stabilizes, he may get to come home tomorrow. He isn't on Lantus, it's Humalin NPH, which we were told today can take 14 to 16 hours to clear from his system, so we'll see where he is after that. We are away from home and away from our normal vet, and kind of out aways from town, so we didn't dare leave him to shop for the Fancy Feast "Gravy Lovers", or something high carb and similar - but we will buy a few cans just to keep on hand for any future issues.
I started a new SS spreasheet for him, with a new name, and now I can't remember how to shorten it to a link in order to add it to his profile. Now that things are calmer, I'll see if I can figure it out. I did it two years ago, but hey, I was younger and smarter then. LOL