In the U.S.—

In Canada—

• Antihyperglycemic agent

Metformin (met-FOR-min) is used to treat a type of diabetes mellitus (sugar diabetes) called type 2 diabetes. With this type of diabetes, insulin produced by the pancreas is not able to get sugar into the cells of the body where it can work properly. Using metformin alone, with a type of oral antidiabetic medicine called a sulfonylurea, or with insulin will help to lower blood sugar when it is too high and help restore the way you use food to make energy.

Many people can control type 2 diabetes with diet alone or diet and exercise. Following a specially planned diet and exercising will always be important when you have diabetes, even when you are taking medicines. To work properly, the amount of metformin you take must be balanced against the amount and type of food you eat and the amount of exercise you do. If you change your diet, your exercise, or both, you will want to test your blood sugar to find out if it is too low. Your health care professional will teach you what to do if this happens.

At some point, this medicine may stop working as well and your blood glucose will increase. You will need to know if this happens and what to do. Instead of taking more of this medicine, your doctor may want you to change to another antidiabetic medicine. If that does not lower your blood sugar, your doctor may have you stop taking the medicine and begin receiving insulin injections instead.

Metformin does not help patients who have insulin-dependent or type 1 diabetes because they cannot produce insulin from their pancreas gland. Their blood glucose is best controlled by insulin injections.

Metformin is available only with your doctor's prescription, in the following dosage form:

Oral
• Tablets (U.S. and Canada)

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For metformin, the following should be considered:

Allergies—Tell your doctor if you have ever had any unusual or allergic reaction to metformin. Also tell your health care professional if you are allergic to any other substances, such as foods, preservatives, or dyes.

Pregnancy—Metformin has not been shown to cause birth defects or other problems in humans. However, metformin is not used during pregnancy. Instead, your doctor may want to control your blood sugar by diet or by a combination of diet and insulin. It is especially important for your health and your baby's health that your blood sugar be closely controlled. Close control of your blood sugar can reduce the chance of your baby gaining too much weight, having birth defects, or having high or low blood sugar. Be sure to tell your doctor if you plan to become pregnant or if you think you are pregnant.

Breast-feeding—It is not known whether metformin passes into human breast milk. Although most medicines pass into breast milk in small amounts, many of them may be used safely while breast-feeding. Mothers who are taking this medicine and who wish to breast-feed should discuss this with their doctor.

Children—Metformin tablets have been tested in children older than 10 years old and, in effective doses, have not been shown to cause different side effects or problems than it does in adults.

Studies with metformin extended-release tablets have been done only in adult patients, and there is no specific information comparing use of this medicine in children with use in other age groups.

Studies with metformin extended-release tablets have not been done in patients younger than 17 years old.

Older adults—Use in older adults is similar to use in adults of younger age. However, if you have blood vessel disorders or kidney problems, your health care professional may adjust your dose or tell you to stop taking this medicine, if necessary.

Other medicines—Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. Do not take any other medicine unless prescribed or approved by your doctor . When you are taking metformin, it is especially important that your health care professional know if you are taking any of the following:

• Alcohol—Small amounts of alcohol taken with meals do not usually cause a problem; however, either larger amounts of alcohol taken for a long time or a large amount of alcohol taken in one sitting without food can increase the effect of metformin. This can keep the blood sugar low for a longer period of time than normal

• Amiloride (e.g., Midamor) or
• Calcium channel blocking agents (amlodipine [e.g., Norvasc], bepridil [e.g., Bepadin], diltiazem [e.g., Cardizem], felodipine [e.g., Plendil], flunarizine [e.g., Sibelium], isradipine [e.g., DynaCirc], nicardipine [e.g., Cardene], nifedipine [e.g., Procardia], nimodipine [e.g., Nimotop], verapamil [e.g., Calan]) or
• Cimetidine (e.g., Tagamet) or
• Digoxin (heart medicine) or
• Furosemide (e.g., Lasix) or
• Morphine (e.g., M S Contin) or
• Procainamide (e.g., Pronestyl) or
• Quinidine (e.g., Quinidex) or
• Quinine (malaria medicine) or
• Ranitidine (e.g., Zantac) or
• Triamterene (e.g., Dyrenium) or
• Trimethoprim (e.g., Proloprim) or
• Vancomycin (e.g., Vancocin)—Use with metformin may cause high blood levels of metformin, which may increase the chance of low blood sugar or side effects

• Acid in the blood (ketoacidosis or lactic acidosis) or
• Burns (severe) or
• Dehydration or
• Diarrhea (severe) or
• Female hormone changes for some women (e.g., during puberty, pregnancy, or menstruation) or
• Fever, high or
• Infection (severe) or
• Injury (severe) or
• Ketones in the urine or
• Mental stress (severe) or
• Overactive adrenal gland (not properly controlled) or
• Problems with intestines (severe) or
• Slow stomach emptying or
• Surgery (major) or
• Vomiting or
• Any other condition that causes problems with eating or absorbing food or
• Any other condition in which blood sugar changes rapidly—Metformin in many cases will be replaced with insulin by your doctor, possibly only for a short time. Use of insulin is best to help control diabetes mellitus in patients with these conditions that without warning cause quick changes in the blood sugar.

• Heart or blood vessel disorders or
• Kidney disease or kidney problems or
• Liver disease (or history of)—Lactic acidosis can occur in these conditions and chances of it occurring are even greater with use of metformin

• Kidney, heart, or other problems that require medical tests or examinations that use certain medicines called contrast agents, with x-rays—Metformin should be stopped before medical exams or diagnostic tests that might cause less urine output than usual. Passing unusually low amounts of urine may increase the chance of a build-up of metformin and unwanted effects. Metformin may be restarted 48 hours after the exams or tests if kidney function is tested and found to be normal

• Overactive thyroid (not properly controlled) or
• Underactive thyroid (not properly controlled)—Until the thyroid condition is controlled, it may change the amount or type of antidiabetic medicine you need

• Underactive adrenal gland (not properly controlled) or
• Underactive pituitary gland (not properly controlled) or
• Undernourished condition or
• Weakened physical condition or
• Any other condition that causes low blood sugar—Patients who have any of these conditions may be more likely to develop low blood sugar, which can affect the dose of metformin you need and increase the need for blood sugar testing

Use this medicine as directed even if you feel well and do not notice any signs of high blood sugar. Do not take more of this medicine and do not take it more often than your doctor ordered. To do so may increase the chance of serious side effects. Remember that this medicine will not cure your diabetes, but it does help control it. Therefore, you must continue to take it as directed if you expect to lower your blood sugar and keep it low. You may have to take an antidiabetic medicine for the rest of your life. If high blood sugar is not treated, it can cause serious problems, such as heart failure, blood vessel disease, eye disease, or kidney disease.

Your doctor will give you instructions about diet, exercise, how to test your blood sugar, and how to adjust your dose when you are sick.

• Blood sugar tests: Testing for blood sugar is the best way to tell whether your diabetes is being controlled properly. Blood sugar testing helps you and your health care team adjust your antidiabetic medicine dose, meal plan, and exercise schedule.
• Diet: The daily number of calories in your meal plan should be adjusted by your doctor or a registered dietitian to help you reach and maintain a healthy body weight. In addition, regular meals and snacks are arranged to meet the energy needs of your body at different times of the day. It is very important that you carefully follow your meal plan.
• Exercise: Ask your doctor what kind of exercise to do, the best time to do it, and how much you should do each day.
• Fluid (water) replacement: It is important to replace the water or fluid that your body uses. Tell your doctor if you have less urine output than usual or severe diarrhea that lasts for more than 1 day.
• On sick days:
  • When you become sick with a cold, fever, or the flu, you need to take your usual dose of metformin, even if you feel too ill to eat. This is especially true if you have nausea, vomiting, or diarrhea. Infection usually increases your need to produce more insulin. Sometimes you may need to be switched from metformin to insulin for a short period of time while you are sick to properly control blood sugar. Call your doctor for specific instructions, especially if severe or prolonged vomiting occurs .
  • Continue taking your metformin and try to stay on your regular meal plan. If you have trouble eating solid food, drink fruit juices, nondiet soft drinks, or clear soups, or eat small amounts of bland foods. A dietitian or your health care professional can give you a list of foods and the amounts to use for sick days.
  • Test your blood sugar and check your urine for ketones. If ketones are present, call your doctor at once. Even when you start feeling better, let your doctor know how you are doing.

Dosing—

The dose of metformin will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of metformin. If your dose is different, do not change it unless your doctor tells you to do so.

The number of tablets that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the amount of sugar in your blood or urine.

• For oral dosage form (tablets):
  • For type 2 diabetes:
    • For patients taking metformin tablets
    • Adults:
      • Metformin alone: At first, 500 milligrams (mg) two times a day taken with the morning and evening meals. Or, 850 mg a day taken with the morning meal. Then, your doctor may increase your dose a little at a time every week or every other week if needed. Later, your doctor may want you to take 500 or 850 mg two to three times a day with meals.
      • Metformin with a sulfonylurea: Your doctor will determine the dose of each medicine.
      • Metformin with insulin: At first, 500 mg a day. Then, your doctor may increase your dose by 500 mg every week if needed.
    • Children up to 10 years of age—Use and dose must be determined by your doctor.
    • Children 10 years of age and over—At first, 500 milligrams (mg) with your morning meal and 500 mg with your evening meal. Then, your doctor may increase your dose a little at a time every week if needed.
    • For patients taking metformin extended-release tablets
    • Adults and teenagers:
      • Metformin alone: At first, 500 milligrams (mg) once daily with the evening meal. Then, your doctor may increase your dose a little at a time every week if needed. If you need more medicine, your doctor may tell you to take more than one dose a day.
      • Metformin with a sulfonylurea: Your doctor will determine the dose of each medicine.
      • Metformin with insulin: At first, 500 mg a day. Then, your doctor may increase your dose by 500 mg every week if needed.
    • Children up to 17 years of age—Use and dose must be determined by your doctor.

Missed dose—

If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

Storage—

To store this medicine:

• Keep out of the reach of children.
• Store away from heat and direct light.
• Keep the medicine from freezing. Do not refrigerate.
• Do not keep outdated medicine or medicine no longer needed. Be sure that any discarded medicine is out of the reach of children.

Your doctor will want to check your progress at regular visits , especially during the first few weeks that you take this medicine.

It is very important to follow carefully any instructions from your health care team about:

• Alcohol—Drinking alcohol may cause very low blood sugar. Discuss this with your health care team.
• Other medicines—Do not take other medicines unless they have been discussed with your doctor. This especially includes nonprescription medicines such as aspirin, and medicines for appetite control, asthma, colds, cough, hay fever, or sinus problems.
• Counseling—Other family members need to learn how to prevent side effects or help with side effects if they occur. Counseling on birth control and pregnancy may be needed because of the problems that can occur in pregnancy for patients with diabetes.
• Travel—Carry a recent prescription and your medical history. Be prepared for an emergency as you would normally. Make allowances for changing time zones, but keep your meal times as close as possible to your usual meal times.

In case of emergency—There may be a time when you need emergency help for a problem caused by your diabetes. You need to be prepared for these emergencies. It is a good idea to:

• Wear a medical identification (I.D.) bracelet or neck chain at all times. Also, carry an I.D. card in your wallet or purse that says that you have diabetes and a list of all of your medicines.
• Have a glucagon kit available in case severe low blood sugar occurs. Check and replace any expired kits regularly.
• Keep some kind of quick-acting sugar handy to treat low blood sugar.

If you are scheduled to have surgery or medical tests that involve x-rays, you should tell your doctor that you are taking metformin . Your doctor will instruct you to stop taking metformin until at least 2 days after the surgery or medical tests. During this time, if your blood sugar cannot be controlled by diet and exercise, you may be advised to take insulin.

Too much metformin, under certain conditions, can cause lactic acidosis. Symptoms of lactic acidosis are severe and quick to appear and usually occur when other health problems not related to the medicine are present and are very severe, such as a heart attack or kidney failure. Symptoms include diarrhea, fast and shallow breathing, severe muscle pain or cramping, unusual sleepiness, and unusual tiredness or weakness.

If symptoms of lactic acidosis occur, you should check your blood sugar and get immediate emergency medical help. Also, tell your doctor if severe vomiting occurs.

Too much metformin also can cause low blood sugar (hypoglycemia) when it is used under certain conditions. Symptoms of low blood sugar must be treated before they lead to unconsciousness (passing out). Different people may feel different symptoms of low blood sugar. It is important that you learn which symptoms of low blood sugar you usually have so that you can treat it quickly and call someone on your health care team right away when you need advice.

• Symptoms of low blood sugar can include: anxious feeling, behavior change similar to being drunk, blurred vision, cold sweats, confusion, cool pale skin, difficulty in concentrating, drowsiness, excessive hunger, fast heartbeat, headache, nausea, nervousness, nightmares, restless sleep, shakiness, slurred speech, and unusual tiredness or weakness.
• The symptoms of low blood sugar may develop quickly and may result from:
  • delaying or missing a scheduled meal or snack.
  • exercising more than usual.
  • drinking a large amount of alcohol.
  • taking certain medicines.
  • if also using insulin or a sulfonylurea, using too much of these medicines.
  • sickness (especially with vomiting or diarrhea).
• Know what to do if symptoms of low blood sugar occur. Eating some form of quick-acting sugar when symptoms of low blood sugar first appear will usually prevent them from getting worse.
• Good ways to increase your blood sugar include:
  • Using glucagon injections in emergency situations such as unconsciousness. Have a glucagon kit available and know how to prepare and use it. Members of your household also should know how and when to use it.
  • Eating glucose tablets or gel or sugar cubes (6 one-half–inch size). Or drinking fruit juice or nondiet soft drink (4 to 6 ounces [one-half cup]), corn syrup or honey (1 tablespoon), or table sugar (dissolved in water).
    • Do not use chocolate. The sugar in chocolate may not enter into your blood stream fast enough. This is because the fat in chocolate slows down the sugar entering into the blood stream.
    • If a meal is not scheduled for an hour or more, you should also eat a light snack, such as crackers or half a sandwich.

High blood sugar (hyperglycemia) is another problem related to uncontrolled diabetes. Symptoms of mild high blood sugar appear more slowly than those of low blood sugar.

• Check with your health care team as soon as possible if you notice any of the following symptoms: Blurred vision, drowsiness, dry mouth, increased frequency and volume of urination, loss of appetite, nausea or vomiting, stomachache, tiredness, or unusual thirst.
• Get emergency help right away if you notice any of the following symptoms: Flushed dry skin, fruit-like breath odor, ketones in urine, passing out, or troubled breathing (rapid and deep). If high blood sugar is not treated, severe hyperglycemia can occur, leading to ketoacidosis (diabetic coma) and death.
• It is important to recognize what can cause the loss of blood glucose control. Calling your doctor early may be important to prevent problems from developing when the following occur. High blood sugar symptoms may occur if you:
  • have a fever or an infection.
  • are using insulin, sulfonylurea, or metformin and do not take enough of these medicines or skip a dose.
  • do not exercise as much as usual.
  • take certain medicines to treat conditions other than diabetes that change the amount of sugar in your blood.
  • overeat or do not follow your meal plan.
• Know what to do if high blood sugar occurs. Your doctor may recommend changes in your antidiabetic medicine dose(s) or meal plan to avoid high blood sugar. Symptoms of high blood sugar must be corrected before they progress to more serious conditions. Check with your doctor often to make sure you are controlling your blood sugar, but do not change your dose without checking with your doctor. Your doctor might discuss the following with you:
  • Delaying a meal if your blood glucose is over 200 mg/dL to allow time for your blood sugar to go down. An extra dose of metformin or an injection of insulin may be needed if your blood sugar does not come down shortly.
  • Not exercising if your blood glucose is over 240 mg/dL and reporting this to your doctor immediately.
  • Being hospitalized if ketoacidosis or diabetic coma occurs.

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if the following side effect occurs:

• Rare
  • Lactic acidosis (quick and severe), including diarrhea, fast shallow breathing, muscle pain or cramping, unusual sleepiness, unusual tiredness or weakness 
  
  

Check with your doctor as soon as possible if the following side effect occurs:

• Rare
  • Low blood sugar (mild), including anxious feeling, behavior change similar to being drunk, blurred vision, cold sweats, confusion, cool pale skin, difficulty in concentrating, drowsiness, excessive hunger, fast heartbeat, headache, nausea, nervousness, nightmares, restless sleep, shakiness, slurred speech 
  
  

Other side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. However, check with your doctor if any of the following side effects continue or are bothersome:

• More common
  • Loss of appetite;  metallic taste in mouth;  passing of gas;  stomachache;  vomiting;  weight loss 
  
  

Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.

Once a medicine has been approved for marketing for a certain use, experience may show that it is also useful for other medical problems. Although this use is not included in product labeling, metformin is used in certain patients with the following medical conditions:

• Polycystic ovary syndrome

Other than the above information, there is no additional information relating to proper use, precautions, or side effects for these uses.