A high blood sugar number is anything above 100 milligrams per deciliter of blood if a person has not eaten for eight hours, according to WebMD. A number of 126 milligrams or higher per deciliter of blood during fasting means that a person has diabetes.
Any number higher than 100 milligrams per deciliter during fasting warrants a close look because it likely indicates prediabetes, says WebMD. Modifying diet and exercise habits may slow or stop the progression from prediabetes to diabetes. Complications of diabetes include kidney failure, vision impairment, nerve damage in various limbs and decreased blood circulation.
A normal blood sugar number is less than 100 milligrams per deciliter of blood when a person fasts and less than 140 milligrams per deciliter two hours after a person eats, explains WebMD.