JANUVIA (Sitagliptin phosphate) is amedication used to treat type 2 diabetesmellitus. It should be as an adjunct to diet and exercise. JANUVIA should not be prescribed for type 1 diabetes mellitus or the treatment or diabetic ketoacidosis. JANUVIA works by inhibiting the enzyme DPP-4 in the gastrointestinal tract. DPP-4 normally shuts off incretin hormones, and incretin hormones are responsible for promoting the digestion process and increasing the release of insulin. By blocking DPP-4, JANUVIA increases the activity of incretin hormones, causing a downstream increase in insulin. The net effect is to lower blood sugar. Combined with diet and exercise, JANUVIA has been shown to decrease hemoglobin A1C, fasting plasma glucose (FPG), and 2-hour postprandial glucose (PPG).