I recently was asked if a blood glucose level of 1300 mg/dl was possible.
Yes, it is! In fact, it’s nowhere near the record; there's a Letter to the Editor of Diabetes Care in the February, 1990 issue (1) that seems to set the record:
The authors describe a 29 year old man, who did not have a diagnosis of diabetes, and who had been previously healthy. The day before admission to the hospital, he was thirsty (attributed to hot weather) and drank 12 liters of Coca-Cola, six cans of pineapple juice with sugar, several liters of orange juice, and sugared water.
On the day of admission, he was found unconscious in his apartment. "Paramedics infused 50 ml of 50% dextrose" (apparently concerned that he might have hypoglycemia). At the Emergency Room, he was "deeply comatose" and severely dehydrated. After lab tests were drawn, he got another 50 ml of 50% dextrose! After getting back the lab results, he was started on more appropriate therapy (insulin and fluids), and gradually improved, and was discharged with "no neurologic deficits."
The authors comment that "given the ease and rapidity of glucose estimation by reagent strips, the practice of indiscriminate administration of dextrose to comatose patients should, in our opinion, be discouraged." I agree.
(1) A Soni, SV Rao, R Bajaj, and G Treser