Nonfasting blood sugar should be less than 140 milligrams per deciliter two hours after a meal, according to Virginia Mason Medical Center. The blood sugar test is used to diagnose diabetes or determine if a person has an increased risk of developing diabetes.
Blood sugar levels vary depending on when a person eats, what foods are eaten, portion sizes and the amount of exercise a person gets, states Virginia Mason Medical Center. Diabetes is diagnosed when a person has a random nonfasting glucose level greater than 200 milligrams per deciliter. Although diabetes causes symptoms such as excessive thirst, fatigue and frequent urination, some people have elevated blood sugar levels without displaying any symptoms.