It's an upstream inhibitor of glucagon. Glucagon signals the body that it has low blood sugar. It tells the liver to produce sugars in response, because the body thinks you're in a fasting state. In a normal person glucagon is inhibited when you eat food, because insulin is released. Insulin tells the body - 'It's Dinner Time!!' - and you're liver production of sugar stops as blood sugar is used up. Apparently this system gets screwed up in people with diabetes, as the balancing act between insulin and glucagon doesn't work properly. Therefore this medication will help the body realize, that when blood sugar is high, to stop liver production of sugars (and possibly tell the pancreas to release insulin), which should aid diabetics in controlling blood sugar levels.