I started my day at noon (well it is Sunday and didnt go to bed until about 3.30am not partying just like to be up late on the computer) anyway - this was the day
I'll get shot for answering in this forum, but I really don't think this a low carb issue.
A few observations
its a good idea to compare your carb intake (whatever it is) and amount of insulin. Eventually you be able to work out reasonably accurate carb/insulin ratios and avoid too many mistakes with too much or too little insulin.
breakfast weetabix 27.4g carbs + orange juice , low sugar .. who knows? 8g carb
Total 35.4g for which you took 18u from a low normal blood glucose level
Lunchtime you were at a higher level ( at the other end of a normal pre meal target)
20 units for lets say 15g carbs (1 slice toast)
You took 2 more units of insulin than at breakfast for less than half the carb intake .(though for many of us protein also counts a bit)
An hour and a half later you have a hypo.... too much insulin and your insulin may not have peaked by then.
Novorapid peaks at about 2hrs dropping to nothing at 51/2 to 6 hrs. (thats one of the reasons for checking levels at 2 hours when you take insulin)
see profile novorapid (URL below)
The normal treatment for a hypo is 10-15g very fast carbs dextrose , glucozade, coke(not normally chocolate..too slow) wait 15 min then recheck blood glucose. If it hasn't risen then you need to treat again. If it's a while to your next meal then eat a small low gi snack ie 1/2 a small sandwich or a piece of fruit. (to be honest I very rarely need to but your insulin was still at peak action )
Sorry, if this isn't new and you've been doing this for years (I haven't read your profile)
http://www.novonordisk.com/diabetes/hcp/pharmaceuticals/novorapid/actionprofile.asp