If a diabetic's blood glucose ("sugar") gets too high (Hyperglycemia), or too low (Hypoglycemia), they can go into diabetic shock and coma. 

Diabetic coma is an extremely dangerous medical condition.  When a diabetes patient is in a coma they appear to be sleeping, but are unconscious and unresponsive to stimulation, including pain stimulation.  A diabetes patient should be rushed to to an emergency room or dial 911 for an ambulance if the diabetic shows  any of these symptoms of coma. 

If the coma is due to Hyperglycemia, doctors will administer intravenous fluids, insulin, sodium and potassium to lower the diabetes patient's blood glucose level.  

If the coma is due to Hypoglycemia, doctors will administer glucagon hormone to raise the diabetes patient's blood glucose level.