Metformin oral tablet comes in two forms: immediate-release and extended-release. The immediate-release tablet is available as the brand-name drug Glucophage . The extended-release tablet is available as the brand-name drugs Glucophage XR, Fortamet, and Glumetza . Both tablet forms are also available as generic drugs. Generics usually cost less than brand-name versions. In some cases, they may not be available in all strengths or forms as brand-name drugs. Why it’s used Metformin oral tablets are used to treat high blood sugar levels caused by type 2 diabetes. They’re used in combination with diet and exercise. This drug may be used as part of a combination therapy. That means you may need to take it with other drugs. How it works Metformin belongs to a class of drugs called biguanides. A class of drugs is a group of medications that work in a similar way. These drugs are often used to treat similar conditions. Metformin works by: reducing the amount of glucose (sugar) made by your liver decreasing the amount of glucose your body absorbs increasing the effect of insulin on your body Insulin is a hormone that helps your body remove extra sugar from your blood. This lowers your blood sugar levels.