Everyone has a different threshold of how low they can go before they run into serious problems. My daughter has been down to 1.8mmol/l at the lowest and she was very drowsy just wanting to fall asleep. She was still able to drink lucozade through a straw which thankfully raised her blood sugars quickly. I'm not sure she would have been able to correct the hypo without help i.e. going to the kitchen to fetch a sugary drink etc. The important thing to do is try not to miscalculate insulin dose (but it does happen, we are only human and make mistakes) and always keep hypo treatments in easy reach if you take insulin. Never leave home without a hypo treatment with you and make sure people around you know how to treat a hypo if you need help. I believe anything under 2.0 mmol/l can result in unconsciousness so you were possibly very close to running into serious problems. I'm glad you are okay and didn't suffer any serious problems.
Due to a serious error in calculating my insulin dose (type2 diabetic) I got a bad hypo of 1.9mmo/L. Although I suffered minor problems (fortunately) it prompts me to ask how low would it have to be to cause serious problems, and why was I so lucky? 