Normal blood sugar levels are under 100 milligrams per deciliter after not eating for eight hours and under 140 milligrams per deciliter two hours after eating, reports WebMD. Before meals, most nondiabetics have blood sugar levels between 70 to 80 milligrams per deciliter.
Fasting blood sugar test levels higher than 125 milligrams per deciliter indicate diabetes, and fasting levels between 100 to 125 milligrams per deciliter indicate prediabetes, explains Mayo Clinic. Random blood sugar test levels higher than 200 milligrams per deciliter suggest diabetes, especially when other symptoms of the disease are present.
Elevated blood sugar levels can damage blood vessels and result in complications such as kidney disease, heart attacks, strokes, nerve damage and vision loss, according to WebMD.