Coincidence, but I had a bad night too last night, woke up with heart racing, felt a bit rough. This morning my vision was quite blurry, sugars at 6.4 at 1:18am and also at 5:17 when I woke with the racing heart (tachycardia). I don't know if I dipped between those times. I have experienced the tach before, but it was many months, even over a hear ago when I was doing nothing about my diabetes.
It is continually amazing me what this body of mine is doing. - unfortunately without being attached to a plethora of machines I'll probably never know.
I'm starting to get quite deep into my studies of the endocrine system and it is totally astonishing how it all works (or not!).
Please let us know if you get any insights and I hope you are feeling a bit better now.