This information is for people who have type 2 diabetes. It tells you about sitagliptin and vildagliptin, treatments used for type 2 diabetes. It is based on the best and most up-to-date research.
Do they work?
Yes, probably. Sitagliptin and vildagliptin are likely to improve your blood glucose control.
What are they?
Sitagliptin and vildagliptin are drugs called DPP-4 inhibitors. They come as tablets that you take once a day, when you are also taking other medicines for diabetes. The brand name for sitagliptin is Januvia. The brand name for vildagliptin is Galvus. You need a prescription from your doctor to get these medicines.
Sitagliptin and vildagliptin are usually used (separately, not together) by people who are already taking either metformin or sulphonylurea tablets, if their diabetes is not under control.  
If you're taking metformin and sulphonylurea tablets together but still have high blood sugar, your doctor might recommend sitagliptin or vildagliptin as a third treatment. 
You may also take sitagliptin in addition to insulin.
Sitagliptin can also be used as the first choice of drug for people who can't take metformin for some reason, perhaps because of side effects.
Doctors sometimes prescribe a similar drug called saxagliptin (brand name Onglyza). However, this is a newer treatment and we haven't yet looked closely at the research on how well it works.
How can they help?
Taking sitagliptin or vildagliptin, either alone or with other medicines, is likely to help reduce your average blood glucose levels ( HbA1c) by about the same amount as most other medicines for diabetes.    However, some research suggests they may not work quite as well as metformin.  
Sitagliptin is also likely to help lower your blood glucose if it's still too high when taking insulin. 
Compared with taking either medicine alone, your haemoglobin A1c level may get better if you take saxagliptin and metformin together . 
How do they work?
These drugs help your body control the level of glucose (sugar) in your blood, by encouraging your body to release more insulin.