Doctors refer to some people as having prediabetes or borderline diabetes when blood sugar is usually in the range of 100 to 125 milligrams per deciliter (mg/dL).

Normal blood sugar levels sit between 70 and 99 mg/dL, whereas a person with diabetes will have a fasting blood sugar higher than 126 mg/dL.

The prediabetes level means that blood glucose is higher than usual but not so high as to constitute diabetes.

People with prediabetes are, however, at risk of developing type 2 diabetes, although they do not usually experience the symptoms of full diabetes.