Stop using this medication and call your doctor at once if you have any of these signs of an allergic reaction: fever; rash; nausea, vomiting, diarrhea, stomach pain; general tiredness, body aches; shortness of breath, cough, sore throat.
Once you have had an allergic reaction to this medication, you must never use it again.
Do not allow this medicine to run out completely before you get your prescription refilled. If you miss several doses, you could have a dangerous or even fatal allergic reaction when you start taking the medicine again. If you stop taking this medication for any reason, talk to your doctor before you start taking the medication again.
Some people have developed a life-threatening condition called lactic acidosis while taking this medicine. Early signs of lactic acidosis generally get worse over time and this condition can be fatal. Get emergency medical help if you have even mild symptoms of lactic acidosis, such as: muscle pain or weakness, numb or cold feeling in your arms and legs, trouble breathing, stomach pain, nausea with vomiting, slow or uneven heart rate, dizziness, or feeling very weak or tired.