Prediabetes is a term used to describe blood glucose levels that are higher than normal, but not high enough for a diagnosis of diabetes. It was earlier called Impaired Glucose Tolerance (IGT), and the current term prediabetes is in use since 2003. General criteria for diagnosing prediabetes and diabetes If a person knows that they have prediabetes, they can take preventative steps to keep type 2 diabetes from developing.