Pre-diabetes includes impaired fasting glucose (IFG) and impaired glucose tolerance (IGT).
IFG is defined as a glucose level of 100 to 125 mg per dL after an overnight 8 to 12 hour fast.
IGT is defined as a two-hour glucose level of 140 to 199 mg per dL after a person drinks a 75-gram glucose solution following an overnight 8 to 12 hour fast.
Prior to developing type 2 diabetes, people almost always have pre-diabetes.
Studies indicate that most people with pre-diabetes develop type 2 diabetes within 10 years.
It is important to note that progression to type 2 diabetes among people with pre-diabetes is not inevitable – as was found in the Diabetes Prevention Program.
Reference
National Institute of Diabetes and Digestive and Kidney Diseases. National Diabetes Statistics fact sheet: General information and national estimates on diabetes in the United States, 2007. Bethesda, MD: U.S. Department of Health and Human Services, National Institutes of Health, 2008.