metformin



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Accepted at over 60,000 pharmacies nationwide

Fortamet, Glucophage, Glucophage XR, Glumetza, Riomet

What is metformin?

Metformin is an oral diabetes medicine that helps control blood sugar levels.

Metformin is for people with type 2 (non-insulin-dependent) diabetes. Metformin is sometimes used in combination with insulin or other medications, but it is not for treating type 1 diabetes.

Metformin may also be used for other purposes not listed in this medication guide.

What is the most important information I should know about metformin?

Do not use metformin if you have kidney disease, or if you are in a state of diabetic ketoacidosis (call your doctor for treatment with insulin).

Before taking metformin, tell your doctor if you have liver disease or a history of heart disease.

Some people have developed a life-threatening condition called lactic acidosis while taking metformin. Get emergency medical help if you have any of these symptoms of lactic acidosis: weakness, increasing sleepiness, slow heart rate, cold feeling, muscle pain, shortness of breath, stomach pain, feeling light-headed, and fainting.

If you need to have any type of x-ray or CT scan using a dye that is injected into a vein, you may need to temporarily stop taking metformin. Be sure the doctor knows ahead of time that you are using this medication.

Know the signs of low blood sugar (hypoglycemia) and how to recognize them, including hunger, headache, confusion, irritability, drowsiness, weakness, dizziness, tremors, sweating, fast heartbeat, seizure (convulsions), fainting, or coma (severe hypoglycemia can be fatal). Always keep a source of sugar available in case you have symptoms of low blood sugar.

What should I discuss with my healthcare provider before taking metformin?

Some people have developed a life-threatening condition called lactic acidosis while taking metformin. Get emergency medical help if you have any of these symptoms of lactic acidosis: weakness, increasing sleepiness, slow heart rate, cold feeling, muscle pain, shortness of breath, stomach pain, feeling light-headed, and fainting.

You may be more likely to develop lactic acidosis if you have congestive heart failure. Older adults may also have a higher risk of developing lactic acidosis. Talk with your doctor about your individual risk.

Do not use this medication if you are allergic to metformin, if you have kidney disease or kidney failure, or if you are in a state of diabetic ketoacidosis (call your doctor for treatment with insulin).

Before taking this medication, tell your doctor if you are allergic to any drugs, or if you have:

  • liver disease; or
  • a history of heart disease.

If you have any of these conditions, you may need a dose adjustment or special tests to safely take metformin.

FDA pregnancy category B. This medication is not expected to be harmful to an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant during treatment.

It is not known whether metformin passes into breast milk or if it could harm a nursing baby. Do not take metformin without first talking to your doctor if you are breast-feeding a baby.

Metformin should not be given to a child younger than 10 years old. Extended-release metformin (Glucophage XR) should not be given to a child younger than 17 years old.

How should I take metformin?

Take this medication exactly as it was prescribed for you. Do not take the medication in larger amounts, or take it for longer than recommended by your doctor. Follow the directions on your prescription label.

Your doctor may occasionally change your dose to make sure you get the best results from this medication.

Take metformin with a meal, unless your doctor tells you otherwise. Some forms of metformin are taken only once daily with the evening meal. Follow your doctor's instructions.

Metformin is only part of a complete program of treatment that also includes diet, exercise, and weight control. It is important to use this medicine regularly to get the most benefit. Get your prescription refilled before you run out of medicine completely.

Do not crush, chew, or break an extended-release tablet (Glucophage XR). Swallow the pill whole. It is specially made to release medicine slowly in the body. Breaking the pill would cause too much of the drug to be released at one time.

To be sure this medication is helping your condition, your blood will need to be tested on a regular basis. Your kidney function may also need to be tested. It is important that you not miss any scheduled appointments.

Your medication needs may change if you become sick or injured, if you have a serious infection, or if you have any type of surgery. Your doctor may want you to stop taking metformin for a short time if any of these situations affect you.

Take care not to let your blood sugar get too low, causing hypoglycemia. You may have hypoglycemia if you skip a meal, exercise too long, drink alcohol, or are under stress.

Know the signs of low blood sugar (hypoglycemia) and how to recognize them:

  • hunger, headache, confusion, irritability
  • drowsiness, weakness, dizziness, tremors
  • sweating, fast heartbeat
  • seizure (convulsions); or
  • fainting, coma (severe hypoglycemia can be fatal).

Always keep a source of sugar available in case you have symptoms of low blood sugar. Sugar sources include orange juice, glucose gel, candy, or milk. If you have severe hypoglycemia and cannot eat or drink, use an injection of glucagon. Your doctor can give you a prescription for a glucagon emergency injection kit and tell you how to give the injection.

Your doctor may have you take extra vitamin B12 while you are taking metformin. Take only the amount of vitamin B12 that your doctor has prescribed.

If you need to have any type of x-ray or CT scan using a dye that is injected into a vein, you may need to temporarily stop taking metformin. Be sure the doctor knows ahead of time that you are using this medication.

Store metformin at room temperature away from moisture, heat, and light.

What happens if I miss a dose?

Take the missed dose as soon as you remember (be sure to take the medicine with food). If it is almost time for your next dose, skip the missed dose and take the medicine at the next regularly scheduled time. Do not take extra medicine to make up the missed dose.

What happens if I overdose?

Seek emergency medical attention if you think you have used too much of this medicine. You may have signs of low blood sugar, such as hunger, headache, confusion, irritability, drowsiness, weakness, dizziness, tremors, sweating, fast heartbeat, seizure (convulsions), fainting, or coma.

An overdose of metformin may cause a life-threatening condition called lactic acidosis. Get emergency medical help if you have any of these symptoms of lactic acidosis: weakness, increasing sleepiness, slow heart rate, cold feeling, muscle pain, shortness of breath, stomach pain, feeling light-headed, and fainting.

What should I avoid while taking metformin?

Avoid drinking alcohol while taking metformin. Alcohol lowers blood sugar and may increase the risk of lactic acidosis while you are taking this medicine.

What are the possible side effects of metformin?

Get emergency medical help if you have any of these symptoms of lactic acidosis: weakness, increasing sleepiness, slow heart rate, cold feeling, muscle pain, shortness of breath, stomach pain, feeling light-headed, and fainting.

Stop using metformin and get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have any of these serious side effects:

  • feeling short of breath, even with mild exertion
  • swelling or rapid weight gain; or
  • fever, chills, body aches, flu symptoms.

Less serious side effects may include:

  • headache or muscle pain
  • weakness; or
  • mild nausesa, vomiting, diarrhea, gas, stomach pain.

This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect metformin?

You may be more likely to have hyperglycemia (high blood sugar) if you are taking metformin with other drugs that raise blood sugar. Drugs that can raise blood sugar include:

  • isoniazid
  • diuretics (water pills)
  • steroids (prednisone and others)
  • phenothiazines (Compazine and others)
  • thyroid medicine (Synthroid and others)
  • birth control pills and other hormones
  • seizure medicines (Dilantin and others); and
  • diet pills, or medicines to treat asthma, colds or allergies.

You may be more likely to have hypoglycemia (low blood sugar) if you are taking metformin with other drugs that lower blood sugar. Drugs that can lower blood sugar include:

  • some nonsteroidal anti-inflammatory drugs (NSAIDs)
  • aspirin or other salicylates (including Pepto-Bismol)
  • sulfa drugs (Bactrim and others)
  • a monoamine oxidase inhibitor (MAOI)
  • beta-blockers (Tenormin and others); or
  • probenecid (Benemid).

Some medications may interact with metformin. Tell your doctor if you are using any of the following drugs:

  • furosemide (Lasix)
  • nifedipine (Adalat, Procardia)
  • cimetidine (Tagamet) or ranitidine (Zantac)
  • amiloride (Midamor) or triamterene (Dyrenium)
  • digoxin (Lanoxin)
  • morphine (MS Contin, Kadian, Oramorph)
  • procainamide (Procan, Pronestyl, Procanbid)
  • quinidine (Cardioquin, Quinidex, Quinaglute)
  • trimethoprim (Proloprim, Primsol, Bactrim, Cotrim, Septra); or
  • vancomycin (Vancocin, Lyphocin).

This list is not complete and there may be other drugs that can interact with metformin. Tell your doctor about all the prescription and over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor.

Where can I get more information?

Your pharmacist can provide more information about metformin.


Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Every effort has been made to ensure that the information provided by Cerner Multum, Inc. ('Multum') is accurate, up-to-date, and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. Multum information has been compiled for use by healthcare practitioners and consumers in the United States and therefore Multum does not warrant that uses outside of the United States are appropriate, unless specifically indicated otherwise. Multum's drug information does not endorse drugs, diagnose patients or recommend therapy. Multum's drug information is an informational resource designed to assist licensed healthcare practitioners in caring for their patients and/or to serve consumers viewing this service as a supplement to, and not a substitute for, the expertise, skill, knowledge and judgment of healthcare practitioners. The absence of a warning for a given drug or drug combination in no way should be construed to indicate that the drug or drug combination is safe, effective or appropriate for any given patient. Multum does not assume any responsibility for any aspect of healthcare administered with the aid of information Multum provides. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the drugs you are taking, check with your doctor, nurse or pharmacist.