Non-fasting blood sugar levels are considered random readings where a person's levels should be no higher than 200 mg/dl, or it indicates type 2 diabetes. A fasting glucose level, on the other hand, should be no higher than 126. Further tests provide insight into how long it takes a person's blood sugar to spike and drop after eating.
Risk factors for type 2 diabetes include having close relatives with the condition, being over 45 years of age, being overweight, not exercising on a regular basis, and having gestational diabetes during pregnancy. Because symptoms can be mild for months or even years, type 2 often is initially indicated during a routine non-fasting blood test.
Diabetes cannot be confirmed by non-fasting blood sugar levels, so physicians require fasting tests as well. Diabetes is suspected if the non-fasting level is higher than 200 mg/dl, especially if the patient also has symptoms of increased thirst and urination, along with fatigue. Even soon after eating, such high blood sugar numbers are considered unhealthy. The physician will advise the person to return for a fasting blood sugar test, which is performed after at least eight hours with no food.
A fasting blood sugar level indicates type 2 diabetes if the reading is higher than 126 on two separate days. Numbers between 100 and 126 are considered impaired, or pre-diabetes, where a person can more easily return to normal levels through diet changes and exercise.
A glucose tolerance test is another type of non-fasting blood sugar diagnostic procedure. The patient typically drinks water with a specific amount of glucose added, and then a health care professional determines how long it takes the blood sugar level to peak and return to normal. Levels should drop back to 100 within 2 to 4 hours. A reading after two hours of 139 or below is considered normal, 140 to 199 pre-diabetic, and 200 and higher indicate type 2 diabetes. The test must be performed on a second day to confirm the diagnosis.
A person with blood sugar over 240 during a non-fasting reading may be asked for a urine sample for a ketone test, particularly if the person is feeling ill. This test checks for a serious condition called ketoacidosis, where a high concentration of acids have built up in the blood due to high sugar levels. In addition, whenever blood sugar reaches this level, the physician likely will immediately prescribe medication to bring the number down.