Hi Dick,
Yes I agree, this cat needs to be started on insulin. Some cats will regulate on diet alone, but most will need insulin injections. They are easy to give and well tolerated. I would recommend a glucose curve at the hospital to determine the best insulin dose for her as cats can respond differently to insulin. Some will regulate on once daily injections, but more often than not twice daily injections are needed. I'd start with something like Vetsulin and determine dosage based on the curve. Some cats, FYI, will need multiple curves the first couple months as their body begins to adapt to having insulin injections.
Hope that helps, let me know if you have any other questions.
Cat Veterinarian
DVM, Emergency Veterinarian; BS (Physiology) Michigan State Univ
The bread may make the GLU go up a little, but not up to the 400's. I would bet that her GLU will be over 400 the next time you test it, and insulin therapy will be needed. I'd be careful how long you wait to start insulin as well as we don't want her going into DKA- diabetic ketoacidosis. These are very sick cats that need days of hospitalization to get them recovered. If any vomiting or lethargy I'd get her in right away.