I try to keep my glucose levels low but within normal ranges and would most definitely treat a 3mmol/l as a hypo . The definition of a severe hypo varies according to level and symptoms experienced but you are approaching the level that can have serious consequences.(not every time but you might not always be 'lucky')
If you don't treat and you become accustomed to functioning with low glucose levels, the level at which you detect hypos may becomer lower than the level at which brain function becomes impaired. This is dangerous, you may not collapse but you may still injure yourself because you're not thinking straight.
http://www.bbdc.org/diabetesmanagement/chapter12.html
You need to use some fast acting glucose, dextrose, lucozade , glucose gel etc. To me they all taste horrible so I don't want to overdose on them. The 'correct' answer is to use 15g fast acting carbs. Personally I need less and treat to get my levels back to normal range rather than above . The amount I use is appropriate for me,we all vary.
If my levels were betwen 3.6 and 4mmol/l I might be a little less likely to treat it quite in the same way. (I'm not in the UK and my doctors tend to use a slightly lower threshold level than in the UK. )
How I act at that level depends on the reason for being low, how I felt, what I'm about to, the time since my last bolus. I would still normally eat some sort of carbs ,unless I was about to sit down and eat. Instead of the glucose 'treatment' I might just use a non 'official' remedy like a small biscuit (8g carb and relatively fast ) or when I'm in the UK I'm partial to a small piece of peppermint aero (not the healthiest choice but quite fast) . My hospitals preferred alternative would be a small piece of fruit. I definitely wouldn't choose protein.(where did you see that?)