He imagines himself to have most likely inadvertently injected too much fast-acting insulin that day.  He was in a hurry, besides which his regimen of constantly checking his blood sugars and injecting insulin in response multiple times daily is so routine, he barely gives it a thought, other than for the purely mechanical equations that ensue. 

When he was younger he had experienced on a few occasions such severely violent hypoglycemic reactions.  He hardly anticipated one would occur when he was on a Toronto transit bus heading toward a destination that would allow him to pick up an important item he had ordered, before then heading downtown to his various appointments.

But occur it did, and he was helpless to forestall it.  As luck had it, the TTC driver, an alert woman who immediately called for help ensured a response that was swift and useful.  The response came from a nearby ambulance service because of their then-close proximity to Humber College's Osler Medical Centre.  The paramedics who knew their stuff were highly organized, professional and administered glucagon.

Then he was ambulanced directly to the William Osler Health Centre.  In retrospect, he felt he should have insisted he was well enough to return home, but he hadn't.  Once at the hospital a doctor examined him and recommended that he agree to remain there overnight for observation, and he agreed.  In his hearing, the doctor instructed the attending nurse, as he wrote those same instructions on the board at the foot of his bed, that his blood sugar levels were to be checked repeatedly throughout the night.

He was hooked up to an IV that dripped glucose steadily intravenously.  It soon became apparent that the nurses on duty had no intention whatever of checking his blood sugar, for none did.  He brought this oversight to their attention and they ignored him.  He asked a new nurse to just check the doctor's instructions and she ignored him, unconcernedly walking out of the room. 

So he kept waking himself up through the night to use his own meter and strips to check his blood sugar.  And the last reading was so high he carefully pulled the IV drip out of his wrist.

When the doctor returned the following morning he relayed to him what had occurred.  And he also had the opportunity to speak with the head nurse to inform her of his experience and his concerns and his impression of the professionalism of the nurses on staff. 

Then he returned home, cancelled a few appointments for the following days, and soon felt his normal self.