I don't think I could operate a blood glusose meter if I was at the point where I would pass out. I've been concious and thinking maybe three or four times but at a point where I couldn't operate my body.
The only time I remember clearly I sincerely believed I would die if I couldn't make my body get up off the ground (I'd been unable to navigate a fallen tree in the forest.) After some undeterminable time in this state I managed to regain control of my body and walk back to my house; my glucagon response kicked in.
Everything has been much more manageable since we moved to human insulin (ooh, terrible genetic engineering ;-). I don't think I would have survived the forest experience on porcine insulin, but these days things happen in a much more measured fashion and, given that I have a functioning glucagon response, I feel fairly safe.
BTW, I don't think people *without* a glucagon response are that common, if, indeed, there are any. A much more interesting question is when people with experience of lows feel the glucagon kicks in. For me it is about 40 on the BG meter.
John Bowler firstname.lastname@example.org