Hi, I am diabetic, and when I had my children, they were born with low blood sugar (despite my hardest efforts!!) the magic number for them not to be considered "low" was 2.6.
I realise that newborns are diffierent from adults, and teh fact that you feel light headed is worth a trip to the drs, but if you had Just eaten...it could be that the food hadn't started to be digested yet?