That is only 12.5 mmol
I wouldn't go to the ER with a sugar like that. I only go to the ER if I have an insanely high sugar AND find ketones by testing my urine at home.
It is a waste of money. For me, I get to take an insulin shot and sit out for awhile, testing every hour until I'm back to a decent range.
I had a low (2.8 mmol or 50 usa) and had an eating fit. I couldn't stop stuffing my face with anything I could get my hands on. Gummy bears.
I woke up this morning feeling higher than a kite at around 3.30am. I tested for ketones, negative and when I woke up at 7:45am, I tested at 16.3, which is just under 300.
If I had a number like that WITH ketones, I would've had DH drive me to the ER. Otherwise, I just take these times as a blip in my control. Blips will happen, it is our job to make sure they don't happen often!
Good luck, I hope you don't have an infection!