Get emergency medical help if you have signs of an allergic reaction to Glucophage: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Some people using metformin develop lactic acidosis, which can be fatal. Get emergency medical help if you have even mild symptoms such as:
unusual muscle pain;
feeling cold;
trouble breathing;
feeling dizzy, light-headed, tired, or very weak;
stomach pain, vomiting; or
slow or irregular heart rate.
Common Glucophage side effects may include:
low blood sugar;
nausea, upset stomach; or
diarrhea.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
 Glucophage side effects (more detail)
