Highest was 40-something when diagnosed 23 years ago, felt awful for weeks and the final straw for my mum was when I lost over a stone in weight in a week. In hosp that night they told my parents if I hadn’t been admitted I’d have died in the next 48 hours…. nice!
I had plenty of HI readings on my meter when I actually bothered to test at uni (thought if I ignored diabetes it would go away… it didn’t!) and recently had a 34, 3 days after going on the pump when the cannula didn’t insert properly.
Scarily only the diagnosis one gave me any real symtoms other than just being ‘a bit thirsty’. 
Lowest and still concious, was 1.2, sat at my desk in work, things looked a bit blurry on my screen and I felt a bit tired! Not good. Other times I can be 3.9 and have a full on cold sweat, blurred vision and the shakes.
I’ve been unconcious and low but never known how low – just woken up (only ever happened at night/early morning) to find 2 blokes in green jumpsuits standing over the bed with a flashing blue-lighted van outside, a very concerned looking boyfriend and a glucose drip in my arm Last one of those was about 4 years ago and I don’t fancy another one thanks.