See also Warning section.
Nausea, vomiting, stomach upset, diarrhea, bloating/gas, or weakness may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly. If stomach symptoms return later (after taking the same dose for several days or weeks), tell your doctor immediately. Stomach symptoms that occur after the first days of your treatment may be signs of lactic acidosis.
Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
Tell your doctor right away if you have any serious side effects, including: change in the amount of urine.
Stop taking this medication and tell your doctor right away if any of these very serious side effects occur: signs of pancreatitis (such as persistent nausea/vomiting, loss of appetite, severe stomach/abdominal/back pain), dark urine, yellowing eyes/skin.
Although this medication by itself usually does not cause low blood sugar (hypoglycemia), low blood sugar may occur if this drug is prescribed with other anti-diabetic medications. Talk with your doctor or pharmacist about all your diabetic medication(s).
Symptoms of low blood sugar include sudden sweating, shaking, fast heartbeat, hunger, blurred vision, dizziness, or tingling hands/feet. It is a good habit to carry glucose tablets or gel to treat low blood sugar. If you don't have these reliable forms of glucose, rapidly raise your blood sugar by eating a quick source of sugar such as table sugar, honey, or candy, or drink fruit juice or non-diet soda. Tell your doctor about the reaction immediately. Low blood sugar is more likely if you drink large amounts of alcohol, do unusually heavy exercise, or do not consume enough calories from food. To help prevent low blood sugar, eat meals on a regular schedule, and do not skip meals. Talk with your doctor or pharmacist about what to do if you miss a meal.
Symptoms of high blood sugar (hyperglycemia) include thirst, increased urination, confusion, drowsiness, flushing, rapid breathing, and fruity breath odor. If these symptoms occur, tell your doctor immediately. Your doctor may need to adjust your diabetes medication(s).
A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.
This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.
In the US -
Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.