A normal blood sugar range is less than 100 milligrams per deciliter following an overnight fast and less than 140 two hours after eating. Throughout the day, sugar levels vary from 70 to 80, although levels within 10 milligrams per deciliter on either side are also normal, explains WebMD.
In general terms, any reading below 100 milligrams per deciliter after fasting is considered in the typical blood sugar range. Blood glucose levels seldom fall below 60 because the liver turns fat and muscle into sugar for fuel. However, WebMD advises that if the level drops below 40, behavior may be affected and symptoms include concentration difficulties, unexplained irritability or anger, confusion, muscles that twitch or feeling unsteady on the feet.