eek lost my post
glucose spills into the urine when bgs go above renal threshold, approximately 250ish. THe kidneys will filter glucose from the blood and 'spill' it into the urine. There is nothing specific 'to do' at this point. Monitoring blood glucose levels will tell you how your cat is responding to insulin and you base dose on that. Glucose spilling into the urine is but one sign that bgs are too high at least at some point.
Hope this helps