A 50-year-old man with diabetes has an altered mental status and is unable to tell you when he last ate or took his insulin. Your glucometer keeps malfunctioning and you are unable to determine his blood glucose level. Which of the following clinical signs would most likely lead you to the correct diagnosis:
A. Rapid and weak pulse
B. Deep and rapid breathing
C. Restlessness and irritability
D. Hypotension and tachycardia