Low Blood Sugar

My question is, at what level are you likely to go into hypoglycemic
shock. I am hypoglycemic unaware. I do not have any symtoms of low
blood sugar until it gets very low. Confusion is the first thing i
can detect as a sign of low blood sugar. Last sunday I eat breakfast
and took my medication, 5/500 glucovance. I normally eat three meals
and three snacks with 20 to 30 grams carbs each time. I got busy on
the computer and missed my mid-morning snack. Around 1:00 pm i
started to fix lunch and could not remember what I was doing.
Checked my sugar and it was 30 mg/dl. I ate some candy and ate
lunch. It went back to normal. I have seen it between 40-60 mg/dl 4
or 5 times.