To determine if Kraft Mac and Cheese has gone bad, start by looking for signs of spoilage. Look for changes in texture, color, or smell of the mac and cheese. If it has a slimy texture, discoloration, or an off smell, it is likely bad and should not be eaten. Additionally, check for any signs of mold. If you see any mold, the mac and cheese should be discarded. Finally, if the expiration date has passed, it is best to discard the mac and cheese.