Prediabetes: Pre- Does Not Mean Preordained.

Although the number of U.S. adults diagnosed with diabetes has decreased in recent years, about 1.4 million new cases of diabetes were diagnosed in Americans aged 18 to 79 in 2014, and that number remains near historic highs. But the prevalence of diagnosed diabetes in the United States is dwarfed by the prevalence of undiagnosed diabetes and prediabetes (Figure 1). As of 2012, about 21 million Americans had diagnosed diabetes. More than 4 times as many—86 million—had prediabetes and an additional 8 million had diabetes that hadn’t been diagnosed (CDC 2014). Prediabetes is an intermediate stage between normal, healthy glucose tolerance and the more severe glucose intolerance that characterizes type 2 diabetes. Without appropriate lifestyle interventions, about 15% to 30% of U.S. adults with prediabetes will go on to develop full-fledged type 2 diabetes within 5 years; on an annual basis, 11% of prediabetic adults who fail to improve their diet and increase their physical activity will develop type 2 diabetes (CDC 2013). Prediabetes encompasses impaired fasting glucose (IFG), impaired glucose tolerance (IGT), or both. It can also be defined with the results from a glycated hemoglobin (HbA1c) test: prediabetes is 5.7% to 6.4% and diabetes is 6.5% or higher (Table 1). Prediabetes does not always lead to type 2 diabetes, although a majority of people with prediabetes—up to 70%—eventually progress to type 2 diabetes. Over the short term (3 to 5 years), about 25% of people with Review