You should not use metformin if you have severe kidney disease, metabolic acidosis, or diabetic ketoacidosis (call your doctor for treatment).
If you need to have any type of x-ray or CT scan using a dye that is injected into your veins, you may need to temporarily stop taking metformin.
Though extremely rare, you may develop lactic acidosis, a dangerous build-up of lactic acid in your blood. Call your doctor or get emergency medical help if you have unusual muscle pain, trouble breathing, stomach pain, dizziness, feeling cold, or feeling very weak or tired.
Before taking this medicine
You should not use metformin if you are allergic to it, or if you have:
severe kidney disease; or
metabolic acidosis or diabetic ketoacidosis (call your doctor for treatment).
If you need to have surgery or any type of x-ray or CT scan using a dye that is injected into your veins, you may need to temporarily stop taking metformin. Be sure your caregivers know ahead of time that you are using this medication.
Tell your doctor if you have ever had:
kidney disease (your kidney function may need to be checked before you take this medicine);
high ketone levels in your blood or urine;
heart disease, congestive heart failure;
liver disease; or
if you also use insulin, or other oral diabetes medications.
You may develop lactic acidosis, a dangerous build-up of lactic acid in your blood. This may be more likely if you have other medical conditions, a severe infection, chronic alcoholism, or if you are 65 or older. Ask your doctor about your risk.
Follow your doctor's instructions about using metformin if you are pregnant or you become pregnant. Controlling diabetes is very important during pregnancy, and having high blood sugar may cause complications in both the mother and the baby. Tell your doctor if you become pregnant while taking metformin.
Metformin may stimulate ovulation in a premenopausal woman and may increase the risk of unintended pregnancy. Talk to your doctor about your risk.
You should not breastfeed while using this medicine.
Metformin should not be given to a child younger than 10 years old. Some forms of metformin are not approved for use by anyone younger than 18 years old.
