The official website of the American Heart Association features charts containing fasting plasma glucose and oral glucose tolerance test blood glucose ranges for prediabetes and diabetes. Prediabetes increases the risk of developing type 2 diabetes, stroke and heart disease, states the American Heart Association.
In patients with prediabetes, blood glucose levels are above normal, but lower than the threshold for a diabetes diagnosis. A fasting plasma glucose range between 100 and 125 milligrams per deciliter indicates prediabetes, and an oral glucose tolerance range of 140 to 199 milligrams per deciliter indicates prediabetes, according to the American Heart Association. Prediabetes causes no symptoms.