The vet told you not to test? I do not understand that. If you had diabetes, or your child had diabetes and you were injecting insulin, you would test the blood to be sure the blood sugar was high enough to give the injection and prevent a life threatening hypoglycemic event. You would not put your life or the life of your child in jeopardy. The same holds true for our furry family members. I have read of other vets telling clients not to test, and find it difficult to understand. If you are injecting insulin, you need to test.
My vet told me to test only midday a few times a week and Idjit did throw us a low blood sugar and started a hypo event. Thank goodness for this board that taught me differently, advised me on how to intervene and the hypo was not critical. Others have not bee so lucky, unfortunately.
It is going to be your decision, but you could be saving your cat's life by testing.