According to the American Diabetes Association (ADA) guidelines, patients with diabetes should strive to achieve fasting blood glucose levels below 131 mg/dL, and levels following meals below 180 mg/dL. Ideally, patients with diabetes can bring their blood glucose levels as close to normal as possible with lifestyle changes and medication. ADA guidelines recommend HbA1C levels below 7%, or an average blood glucose level below 154 mg/dL.

Sources:

http://www.mayoclinic.org, https://www.health.harvard.edu