Study visit: Non-diabetic subjects will be requested to fast overnight and to avoid changes in non-steroidal anti-inflammatory agents or medications that block the renin-angiotension system. Subjects with diabetes will be asked to eat a light breakfast the morning of the study visit. Subjects will be asked to maintain adequate oral hydration and to ingest two to three glasses of non-caffeinated beverages prior to arrival on the morning of the study visit to facilitate a timed urine collection during the study visit. If the subject feels that he/she is unable to void upon arrival, he/she will be given 2 to 3 additional non-caffeinated beverages and will be given approximately 1 beverage every hour for the remainder of the study visit.