Metformin is used with a proper diet and exercise program and possibly with other medications to control high blood sugar. It is used in patients with type 2 diabetes. Controlling high blood sugar helps prevent kidney damage, blindness, nerve problems, loss of limbs, and sexual function problems. Proper control of diabetes may also lessen your risk of a heart attack or stroke. Metformin works by helping to restore your body's proper response to the insulin you naturally produce. It also decreases the amount of sugar that your liver makes and that your stomach/intestines absorb.

This section contains uses of this drug that are not listed in the approved professional labeling for the drug but that may be prescribed by your health care professional. Use this drug for a condition that is listed in this section only if it has been so prescribed by your health care professional.

This drug may also be used with lifestyle changes such as diet and exercise to keep people who are at high risk for diabetes from becoming diabetic. It may also be used by women with a certain disease of the ovaries (polycystic ovarian syndrome). Metformin may make menstrual cycles more regular and increase fertility.

Read the Patient Information Leaflet if available from your pharmacist before you start taking metformin and each time you get a refill. If you have any questions, consult your doctor or pharmacist.

Take this medication by mouth as directed by your doctor, usually once daily with the evening meal. Drink plenty of fluids while taking this medication unless otherwise directed by your doctor.

Do not crush or chew this medication. Doing so can release all of the drug at once, increasing the risk of side effects. Also, do not split the tablets unless they have a score line and your doctor or pharmacist tells you to do so. Swallow the whole or split tablet without crushing or chewing.

The dosage is based on your medical condition, response to treatment, and other medications you may be taking. Be sure to tell your doctor and pharmacist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products). To reduce your risk of side effects (such as upset stomach), your doctor may direct you to start this medication at a low dose and gradually increase your dose. Follow your doctor's instructions carefully.

Take this medication regularly in order to get the most benefit from it. Remember to use it at the same time each day.

If you are already taking another diabetes drug (such as chlorpropamide), follow your doctor's directions carefully for stopping/continuing the old drug and starting metformin.

Check your blood sugar regularly as directed by your doctor. Keep track of the results, and share them with your doctor. Tell your doctor if your blood sugar measurements are too high or too low. Your dosage/treatment may need to be changed.

See also Warning section.

Nausea, vomiting, stomach upset, diarrhea, weakness, or a metallic taste in the mouth may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly. If stomach symptoms return later (after taking the same dose for several days or weeks), tell your doctor right away. Stomach symptoms that occur after the first days of your treatment may be signs of lactic acidosis.

An empty tablet shell may appear in your stool. This effect is harmless because your body has already absorbed the medication.

Remember that this medication has been prescribed because your doctor 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.

Metformin does not usually cause low blood sugar (hypoglycemia). Low blood sugar may occur if this drug is prescribed with other diabetes medications. Talk with your doctor or pharmacist about whether the dose of your other diabetes medication(s) needs to be lowered.

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 right away. 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. Check with your doctor or pharmacist to find out what you should do if you miss a meal.

Symptoms of high blood sugar (hyperglycemia) include increased thirst/urination. If these symptoms occur, tell your doctor right away. Your doctor may need to adjust your diabetes medication, exercise program, or diet.

Stop taking this medication and tell your doctor right away if this very serious side effect occurs:

• lactic acidosis (see Warning section)

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 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

See also Warning section.

Before taking this medication, tell your doctor or pharmacist if you are allergic to metformin; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• severe breathing problems (such as obstructive lung disease, severe asthma)
• blood problems (such as anemia, vitamin B12 deficiency)
• kidney disease
• liver disease

Before having surgery or any X-ray/scanning procedure using iodinated contrast, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products). You may need to stop this medication for a short time for the surgery/procedure. Ask your doctor or dentist for instructions before your surgery/procedure.

You may experience blurred vision, dizziness, or drowsiness due to extremely low or high blood sugar. Do not drive, use machinery, or do anything that needs alertness or clear vision until you are sure you can perform such activities safely.

Limit alcohol while using this medication because it can increase your risk of lactic acidosis and developing low blood sugar.

High fever, "water pills" (diuretics such as hydrochlorothiazide), too much sweating, diarrhea, or vomiting may cause dehydration and increase your risk of lactic acidosis. Stop taking this medication and tell your doctor right away if you have prolonged diarrhea or vomiting. Be sure to drink enough fluids to prevent dehydration unless your doctor directs you otherwise.

It may be harder to control your blood sugar when your body is stressed (such as due to fever, infection, injury, or surgery). Consult your doctor because increased stress may require a change in your treatment plan, medications, or blood sugar testing.

Older adults may be a greater risk for side effects such as low blood sugar or lactic acidosis.

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor. Your doctor may direct you to use insulin instead of this product during your pregnancy. Follow your doctor's instructions carefully.

Metformin can cause changes in the menstrual cycle (promote ovulation) and increase the risk of becoming pregnant. Consult your doctor or pharmacist about the use of reliable birth control while using this medication.

Metformin passes into breast milk in small amounts. Consult your doctor before breastfeeding.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Beta-blocker medications (such as metoprolol, propranolol, glaucoma eye drops such as timolol) may prevent the fast/pounding heartbeat you would usually feel when your blood sugar falls too low (hypoglycemia). Other symptoms of low blood sugar, such as dizziness, hunger, or sweating, are unaffected by these drugs.

Many drugs can affect your blood sugar, making it harder to control. Before you start, stop, or change any medication, talk with your doctor or pharmacist about how the medication may affect your blood sugar. Check your blood sugar regularly as directed and share the results with your doctor. Tell your doctor right away if you have symptoms of high or low blood sugar. (See also Side Effects section.) Your doctor may need to adjust your diabetes medication, exercise program, or diet.

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669. Overdose can cause lactic acidosis. Symptoms of overdose may include: severe drowsiness, severe nausea/vomiting/diarrhea, rapid breathing, slow/irregular heartbeat.

Do not share this medication with others.

Attend a diabetes education program to learn more about how to manage your diabetes with medications, diet, exercise, and regular medical exams.

Learn the symptoms of high and low blood sugar and how to treat low blood sugar. Check your blood sugar regularly as directed and share the results with your doctor.

Lab and/or medical tests (such as kidney function, liver function, blood sugar, hemoglobin A1c, complete blood counts) should be done before you start taking this medication and while you are taking it. Keep all medical and lab appointments. Consult your doctor for more details.

If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.

Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.

Your condition can cause complications in a medical emergency. For information about enrolling in MedicAlert, call 1-888-633-4298 (US) or 1-800-668-1507 (Canada).