Still on Humulin N has been on three units for years and had this hypo 12 hours after a shot. I home test and will try tonight but vet said to give tonight as now she has been without for 24 hours.
Did you change anything recently? Food? She could be going into remission. Give her half the dose of normal and get a test in a few hours. Better too high for a while than a hypo again next time she might not survive it.