Metformin is used with a proper diet and exercise program to control high blood sugar. It is used in patients with type 2 diabetes. Controlling high blood sugar helps prevent kidney damage, blindness, nerve problems, loss of limbs, and sexual function problems. Metformin works by helping to restore the body’s proper response to the insulin the body naturally produce. It also decreases the amount of sugar that the liver makes and that the stomach/intestines absorb.