There are several different tests that can be used to determine the average blood sugar level. Tests are often performed to determine whether a patient has Diabetes, hypoglycemia or to monitor treatment for diabetes. Blood samples can be analyzed to determine blood sugar levels. Factors including diet, physical activity, hormones, stress and medications can affect the results of blood sugar levels.FastingThe tests performed to determine blood sugar levels are given differently to determine how the patient's ability to process sugar or glucose. The blood plasma value is analyzed through vein blood or through a finger-prick test. A fasting blood test is given after the patient has not eaten for at least eight hours. The average blood sugar level for this type of test is 70 to 99 mg of glucose per deciliter of blood.RandomThe random test is given at any time no matter what the patient has eaten. Average blood sugar levels for this test are between 70 to 125 mg per deciliter. Anything over 140 mg is indication for borderline diabetes also referred to as Impaired Glucose Tolerance (IGT). According to the American Diabetes Association, approximately 11 percent of people with prediabetes develop Type 2 Diabetes. If results are over 200 mg, Type 1 or Type 2 diabetes may be suspected and need further testing.Oral GlucoseA common test for blood sugar is the oral glucose tolerance test. This is often given during pregnancy to determine whether a patient has gestational diabetes. Two blood tests determine how the body responds to glucose. The first is taken after hours of fasting. The second round of blood is taken an hour or more after a sugar solution is consumed. The average blood sugar levels should remain under 140 mg/dL after the second test. Anything over 140 mg/dL is considered possibly prediabetic.Alternatively, blood glucose below 40 mg/dL in women and 50 mg/dL in men could indicate hypoglycemia or low blood sugar. Causes for hypoglycemia include a tumor, malnutrition, thyroid conditions, Addison's disease or certain medications.The average blood sugar level can be monitored from home with a finger-prick analysis to check postprandial blood sugar levels. Keeping the blood sugar levels consistent is important to protect the liver, cholesterol levels and heart healthy.