The service I just completed my internship at had glucometers that tap out around 600 before reading only, "HI," however I treated a late 20s male pt with such a reading who was complaining of nausea/vomiting with pretty substantial abdominal pain, to the point we had to pick him up and move him and he fiercely guarded his abdomen after initial palpation. He had about 4-6 episodes of emesis just in the time I saw him and had been like that for a few days so I loaded him up with fluid. Good call, had never seen a really symptomatic DKAer before that.