Should he have a blood reading of 3.6 an hour after a balanced meal? Nothing diagnosed, just borrowed my grans blood monitor after a hunch.
Brief history - he's 32. Always reacted very strongly to food. Hyperactive child, so excessive sugar and additives were removed from diet. He now has huge peaks and troughs in energy levels. When it dips he literally cannot keep awake. He physically can't - it's like watching the curtains close on his brain. He's moody and angry when he wakes. Occasionally wakes disorientated or confused. 
He's fine at work (teacher) or when driving but I think its the adrenaline keeping him going. He has trouble concentrating sometimes - It bothers him too.
I used to be upset or angry but I've been watching him closely and he cannot help or fight the tiredness.
He plays competitive sport and does some form or exercise at least 5 days a week. (again I think the adrenaline keeps him going there).
He follows a good diet - good protein and fats, complex carbs. Plenty of fruit and veg. Natural sugar.
I've worked out he needs approx 4,000 calories a day to keep his weight up 
. Which is a huge amount, especially when done healthily.
Up until the point I checked yesterday he'd eaten:
Bowl of porridge, banana, almonds, white coffee.
Tray of sushi, couple of daughters sweets.
Chicken, beef, salad & brown bread.
He then conked out on the floor for half an hour....
As he simply not eating enough, or could it be that his body is not processing sugar as it should be?