Study participants, who were all aged between 20 and 70, were recruited from health checkup center at Ilsan hospital (Gyeonggi-do, Korea) and the advertisements in local newspaper. After the glucose screening test, subjects with IFG (100 mg/dL ≤ fasting blood glucose ≤ 125mg/dL), IGT (140mg/dL ≤ 2-h OGTT), or newly-diagnosed T2DM (fasting glucose ≥ 126 mg/dL) were enrolled in this study. Exclusion criteria that all selected patients met were: 1) Taking glucose-lowering medications or having insulin injections. 2) Chronic alcoholism or having an evidence or alcoholism. 3) Pregnant or in breast feeding. 4) Having chronic gastrointestinal disorders. 5) Showing signs of nutrient deficiency of malnutrition. 6) Patients with serious kidney problems. 7) Patients with serious liver problems. 8) Patients whose job could be a threat when hypoglycemia occurs. 9) Patients who have experienced the complications such as headache, insomnia, heart palpitations and raised blood pressure after eating red ginseng. 10) Other patients who were considered unsuitable for this study by the researchers