For these without diabetes, it's less than 140 mg/dL, in response to Virginia Mason Diabetes Care. You probably have diabetes, your physician will assist you determine how steadily you might want to test your sugar degree. For individuals who haven't got diabetes, maintaining a food log and noting ranges of fatigue or different symptoms may help determine spikes in blood sugar and the cause of fatigue. Glycemic Index: The speed at which completely different carbohydrates elevate blood sugar varies