Thank you for the query. I would like to enquire about your age, gender, duration of diabetes and whether there is any impairment of renal parameters as per your blood investigations. I would also like to know your sugar control status (Fasting blood sugar, post prandial blood sugar and HbAic) Both Metformin and Januvia (Sitagliptin) are oral antidiabetics with their own merits and demerits. Metformin belongs to class of drug called Biguanide, and traditionally they have been used as first line oral drugs for diabetes. They have an advantage since they are weight neutral (rather they help to reduce weight) and do not cause hypoglycemia. Metformin is usually not used in the following conditions - Gastrointestinal intolerance (diarrhea, nausea), deranged renal function tests (serum creatinine more than 1.5mg% in male subjects) and lactic acidosis (important for critical care subjects). Metformin is also known to cause Vitamin B12 deficiency and subsequent neuropathy. Some physicians do not prefer giving metformin, in a back ground of cardiac disease (like acute myocardial infarction i.e. heart attack) Sitagliptin belongs to a class of drugs called DPPIV inhibitors. Like metformin, they too don t cause hypoglycemia and are weight neutral. They usually do not have the gastro-intolerance side effects like metformin, but in renal impairment some dose reduction is advised (though not totally eliminated like metformin). The main drawback of these drugs are that they are expensive. In case one experiences upper abdominal pain while on these drugs, consulting the physician is needed, since it has been reported to cause pancreatitis. Since, you have not provided enough details, it is difficult to say, why exactly your physician chose Sitagliptin over Metformin. You can check the parameters mentioned above and compare with yours. I would recommend you to consult your physician, and put forth your query. I am sure you shall get an explanation. Hope this helps you out. Regards Dr. Ayusmati Thakur