Januvia (sitagliptin) is a type 2 diabetes oral medication in the DPP-4 inhibitor class of drugs. It lowers blood glucose by slowing the inactivation of GLP-1, a compound in the body that lowers blood glucose levels. Because type 2 diabetes medications act in different ways to lower blood glucose levels, providers will often prescribe multiple drugs to a patient. Several of the more popular combinations of oral drugs can be prescribed together in a single pill. Each medication has its own side effects. Read labels carefully to be sure you know what they are.