There are a number of less common, but more serious, side effects of glyburide and metformin that you should report to your healthcare provider. These include but are not limited to:
Signs of lactic acidosis, including muscle pain; dizziness or lightheadedness; trouble breathing; abdominal pain (or stomach pain); feeling cold, tired, or weak; and a slow or irregular heartbeat (see Metformin and Lactic Acidosis)