Yes, this is a very appropriate and logical treatment change. Since Losartan was not successfully controlling your blood pressure, your doctor switched you to Olstan 40 mg (Olmesartan). Olmesartan is a stronger, longer-acting medication in the same class that provides superior 24-hour blood pressure control and protects your kidneys, which is vital for diabetic patients. To manage your poorly controlled diabetes, your doctor added Sitagliptin 100 mg, a medication that effectively helps lower blood sugar levels. Together, these medications target both conditions much more aggressively. Please monitor your blood pressure and blood sugar regularly as you transition.