Prediabetes is a condition where blood sugar levels are higher than normal but not high enough to be diagnosed as diabetes. The American Diabetes Association (ADA) diagnoses diabetes based on certain blood sugar thresholds including a hemoglobin A1c level of 6.5% or higher, a fasting blood glucose of 126 mg/dL or higher, or a 2-hour plasma glucose of 200 mg/dL or higher during an oral glucose tolerance test. Left untreated, prediabetes can lead to a diagnosis of type 2 diabetes.