"Ketones are high when availability of glucose is low" - it seems the body calculates this based on the amount of insulin available, which is why you can eat nothing (and have no basal) and have a BG spike.
Right -- because you have insufficient insulin available, cells cannot utilize the glucose. So your blood glucose rises. If BG is too high for too long, ketones build up, leading to diabetic ketoacidosis (bad), which is different than the ketosis (good) sought by a ketogenic dieter.
People with T1D are taught to check keytones if BG is very high (CDC says > 240 mg/dL; we were taught > 300) for an extended period of time, or also when sick.
