Visit 1: You will come to the Diabetes and Metabolic Research Center having refrained from taking your routine medications and having not eaten in the last 8 hours, avoided using caffeine-containing beverages and tobacco products in the last 10 hours, and having had no alcoholic beverages in the last 24 hours. In addition, you should refrain from taking any nonprescription drugs and avoid engaging in any vigorous exercise for 48 hours before testing.