People with high fasting glucose can develop type 2 diabetes with the passage of time. This study is being done to determine the effect of a novel medication in people with this elevated fasting glucose. Sitagliptin is a substance that raises levels of a hormone normally found in the blood. This hormone, called glucagon-like peptide-1 (GLP-1), is normally released by the intestine in response to the presence of food. This hormone acts like a messenger between the intestine and the pancreas to raise insulin levels, and therefore, lower blood sugars. Sitagliptin is effective in people with diabetes, however, this study is being done to determine if Sitagliptin is effective in people with high fasting glucose who do not yet have diabetes.