Before you begin taking a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should take this medication.
Alcohol intake: Anyone taking metformin should avoid excessive alcohol intake.
Blood sugar control: If you have fever, trauma, infection, or surgery, you may have a temporary loss of blood sugar control. At such times, your doctor may think it is necessary to stop metformin and temporarily inject insulin. Metformin may be started again after the problem is resolved.
Blood sugar monitoring: Monitor your blood sugar regularly at intervals as discussed with your doctor or diabetes educator.
Diabetes complications: The use of metformin (or any other medication used for diabetes) will not prevent the development of complications particular to diabetes mellitus (e.g., kidney disease, nerve disease, eye disease).
Diet: Metformin is a treatment to be taken in combination with a proper diet. Metformin is not a substitute for proper diet.
Dye or contrast agents: If you are going to have an X-ray procedure that uses dye or a contrast agent, you may need to stop taking this medication for a short time. Contact your doctor for instructions.
Kidney problems: If you have kidney problems, your doctor should closely monitor your condition while you are taking metformin, as it may affect kidney function.
Lactic acidosis: Lactic acidosis is a rare but serious problem that occurs due to metformin accumulation (i.e., the body doesn't get rid of it fast enough) during treatment. If you have severe kidney disease you are at higher risk of developing lactic acidosis. Since alcohol may increase the risk of lactic acidosis, do not drink a lot of alcohol over the short- or long-term while taking this medication. When it does occur (very rarely), it is fatal in 50% of cases. There have been no reports of lactic acidosis in Canada when metformin was used as directed. If you experience symptoms of lactic acidosis (e.g., weakness, tiredness, drowsiness, unusual muscle pain, trouble breathing, stomach pain with nausea, vomiting or diarrhea, feeling cold, dizziness, light-headedness, or slow or irregular heartbeat), stop taking this medication and get immediate medical attention.
Liver function: Decreased liver function has been linked to lactic acidosis. This medication is not recommended for people with severely reduced liver function. If you have moderately reduced liver function, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.
Low blood sugar: Under usual circumstances, low blood sugar does not occur for people who take only metformin. Low blood sugar could occur when not enough food is eaten, especially when strenuous exercise is undertaken at the same time or when large amounts of alcohol have been consumed.
Reduced response: Over a period of time, you may become progressively less responsive to a particular treatment for diabetes because your diabetes worsens. If metformin fails to lower blood sugar to target levels, talk to your doctor. Your doctor may want to stop metformin or recommend another medication.
Surgery: This medication should be stopped temporarily for surgery (except for minor surgery where food and fluid intake is not restricted). You will be restarted on this medication once you are eating and drinking and your kidney function has been tested and is normal. Talk to your doctor for specific instructions.
Vitamin B12 levels: This medication may decrease vitamin B12 levels. Your doctor will monitor your B12 levels with blood tests while you are taking this medication.
Pregnancy: This medication should not be used during pregnancy. If you become pregnant while taking this medication, contact your doctor immediately.
Breast-feeding: Metformin is believed to pass into breast milk. This medication should not be used if you are breast-feeding.
Children: The safety and effectiveness of this medication have not been established for children.
Seniors: Kidney function often decreases with age. As a result, seniors may be more likely to experience side effects of this medication.