Welcome back, Crispie. The prednisone raises blood sugar by itself so while you are on it, you do have to cut out carbs and your doctor might even raise the dosage of the metformin if you're on it for a long time. If it's just a short time, the doctor might not change your dosage but in order to help keep your blood sugar lower, cut out all carbs like bread, rice and potatoes.
Sorry you have to deal with that. I'm sure it's miserable in this hot weather!
diabetes type 2 controlled by diet and exercise and
very low carb way of eating