Medically Reviewed by Dr. Harshi Dhingra, M.D.

Last Reviewed: Nov 10, 2023

Drug Details

Generic Name:


Common Brands:

Glucophage, Glucophage XR*, Fortamet, Glumetza, Riomet  

*Glucophage XR (brand name) has been discontinued in the US; this includes the 500 mg and 750 mg oral extended tablet manufactured by EMD SERONO INC.


Prescription only

Therapeutic Class:


Forms: Oral tablet: 500 mg, 850 mg, 1000 mg

  • Extended-release oral tablet (Glucophage XR): 500 mg, 750 mg
  • Oral solution is available under other brand names and the generic formulation.


By mouth

Therapeutic Uses:

Type 2 diabetes mellitus

Controlled Status:

Not a controlled substance

What is metformin?

Metformin (met for man) belongs to a category of drugs called biguanides. It is an oral prescription medication used to control blood glucose levels. Along with lifestyle changes, metformin is used to prevent and treat type 2 diabetes. Treatment with metformin can help to reduce the risk of diabetes complications such as heart disease, stroke, kidney disease, nerve damage, and eye problems. 

There may be other uses of metformin - your pharmacist or physician can give you further information.

Who can take metformin?

Metformin can be prescribed to adults and children aged 10 years and older with type 2 diabetes. Metformin is not indicated for the treatment of type 1 diabetes.

Metformin may be used in combination with other medications or insulin.


What is metformin used for?

Metformin is a prescription oral anti-diabetic medicine that is used to prevent and treat type 2 diabetes mellitus.

How does metformin work?

  • Metformin works in several different ways to control blood sugar levels: 
  • Metformin improves insulin sensitivity, i.e., it increases the body’s response to the insulin hormone. By decreasing insulin resistance, the cells in your body can absorb and use sugar more effectively, which, in turn, reduces the amount of sugar in the blood.
  • Your body also produces sugar naturally. Metformin reduces the amount of glucose made by the liver, where most sugar production occurs. 
  • Sugar enters your body through food and beverages. Metformin reduces the amount of glucose absorbed from food through the intestines. As a result, less sugar makes it into the bloodstream. 

By controlling blood sugar levels, metformin helps prevent potentially life-threatening complications of diabetes, such as heart disease and stroke.

What are metformin doses?

Metformin is available as an immediate-release tablet, extended-release tablet, and oral suspension (liquid). 

The immediate-release tablet is taken with meals 1-3 times a day. The extended-release form is taken once a day with the evening meal. The available Metformin doses are 500 mg, 850 mg, and 1000 mg.

Doctors usually prescribe metformin 500 mg twice daily by mouth or 850 mg once daily by mouth with meals as a starting dose. 

Do not take more or less metformin than prescribed. Your doctor will start you on a low metformin dose and slowly increase the dose based on your response to the medicine and tolerability (side effects). The dose may be increased no more often than once every 1-2 weeks. Metformin’s maximum recommended daily dose is 2550 mg in adults and 2000 mg in pediatric patients (10-16 years), given in divided doses with meals. Doses above 2000 mg are typically better tolerated if the medicine is taken three times a day with meals. You will need to monitor your blood glucose levels carefully to see how well metformin is working.


How should I take metformin?

Take metformin as directed by your physician and/or pharmacist. This prescription drug is to be taken orally (by mouth) with water. It is best to take metformin with meals to reduce digestive side effects. Swallow the tablet whole - do NOT crush, cut, or chew metformin tablets. 

Follow the directions on your prescription label for the correct metformin dosage and frequency. Take your medicine regularly at around the same time every day - this will help you remember to take your medicine. Do not take more metformin or take it more frequently than prescribed. Metformin does not cure diabetes. Continue taking the medicine even if you feel well and your blood sugar is under control. Do not stop metformin without talking to your doctor first. 

Metformin may be given to children 10 years of age and older. The starting dose in children is usually 500 mg by mouth twice a day. If needed, the dose can be increased at weekly intervals, not to exceed 2000 mg by mouth per day. Speak with your pediatrician regarding the appropriate dose for your child and about special care and precautions while using metformin in children.

Missed dose: If you forget to take your dose of metformin, take the medicine as soon as you remember. However, if it is nearly time for your next dose, skip the missed dose and take the next metformin dose at the regular time. Do NOT take a double dose to make up for the missed dose.

Storage: Store metformin at controlled room temperature (between 20°-25° C (68°-77° F); variations in temperature are allowed up to (15°-30° C or 59°-86° F) The drug should be away from moisture, heat, and direct light in a tightly closed container. Keep all non-prescription and prescription drugs, including metformin, out of reach of children.

Unused medicine: Throw away any unused metformin after the expiration date. Learn more about proper medication disposal

NOTEThis sheet is a summary and may not contain all possible information. If you have questions about metformin, talk to your doctor, pharmacist, or health care provider.


Discounted prices for metformin start at $10.95.

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Side Effects

Metformin Side Effects

The most common side effects of metformin include:

  • Diarrhea
  • Stomachache
  • Bloating
  • Gas
  • Indigestion
  • Heartburn
  • Constipation
  • Headache
  • Metallic taste in the mouth
  • Skin flushing
  • Nail changes
  • Muscle aches

Please tell your doctor if these metformin side effects are severe, do not go away, go away but come back again, or develop some time after you start taking the medication. 

Some of the side effects of metformin are more serious. You should contact your doctor without delay or get emergency treatment for the following side effects:

  • Chest pain
  • Rash
  • Difficulty breathing
  • Irregular heart rate
  • Dizziness

The above list may not include all the potential side effects of metformin. Talk to your doctor if you have severe side effects or if the side effects do not improve over time. You can also report unusual Metformin side effects to the Food and Drug Administration at 1-800-FDA-1088.

Can metformin cause nausea and diarrhea?

Gastrointestinal side effects are common in patients taking metformin. Up to 75% of those who are taking metformin experience diarrhea, nausea, vomiting, and/or abdominal pain. Taking metformin with food or snacks can help ease these tummy side effects, and the good news is that these bothersome side effects tend to get better after a few weeks once your body gets used to this medication.

Does metformin cause constipation?

Rarely, metformin can cause constipation. To help avoid constipation during metformin treatment, drink enough water, get enough exercise, and eat fiber-rich foods. Notably, one of the signs of low B12 levels is constipation. Let your doctor know if constipation persists. A B12 supplement may be helpful in many cases.

What are the long-term side effects of metformin?

Long-term side effects of metformin can include vitamin B12 deficiency. Signs of a vitamin B12 deficiency include tiredness, dizziness, difficulty breathing, and feeling faint. Low B12 levels can also cause some digestive problems, such as nausea, bloating, constipation or diarrhea.

What are the side effects of 1,000 mg of metformin?

Both metformin formulations, immediate-release (IR) and extended-release (ER), are available in 500-milligrams (mg) and 1000-mg strengths, and these two strengths can cause the same side effects. The side effects of metformin 1000mg would include gastrointestinal (GI) side effects such as nausea, vomiting, diarrhea, and gas, especially at the beginning of therapy when your body is still getting used to the effects of this medication. However, the concept of higher doses leading to more significant side effects is also relevant here. Therefore, to alleviate the side effects of metformin 1000mg, metformin is typically started at 500 mg by mouth twice a day or 850 mg by mouth once daily. Taking metformin with food or snacks can also help reduce some of the tummy problems. These GI side effects from metformin are very common, and it is expected to improve after a few weeks. Let your doctor know if these GI symptoms persist. Dosage adjustment or switching to the extended-release (ER) formation can help in many cases.

Can metformin make you tired?

Long-term use of metformin can potentially cause vitamin B12 deficiency, which can cause you to feel more tired.

Can metformin reduce your appetite?

Taking metformin can indirectly reduce your appetite. Metformin is known to cause tummy upset, including symptoms like diarrhea, bloating, and nausea, which, in turn, can cause loss of appetite.

Can metformin cause sweating?

Metformin causes changes in your blood sugar levels. Increased sweating is one of the early signs of hypoglycemia (low blood sugar), in addition to hunger, feeling anxious, and shakiness. You should be aware of the signs and symptoms of high and low blood sugar and know what to do if you develop these symptoms.

Metformin Overdose: Under certain conditions, an overdose of metformin can cause a serious, potentially life-threatening condition called lactic acidosis. Symptoms of metformin overdose can include symptoms of hypoglycemia (low blood glucose levels), weakness, extreme tiredness, nausea, vomiting, stomach pain, decreased appetite, shortness of breath, rapid and deep breathing, lightheadedness, dizziness, abnormally slow or fast heartbeat, feeling cold, flushing of the skin, and muscle pain. If you experience any of these symptoms, stop taking metformin and call your doctor immediately. NOTE: Metformin is a prescription medicine to be used only by you - never share your medication with others or use someone else’s metformin.

Source: FDA


What are the risks of taking metformin?

Metformin can cause serious health problems, especially in certain high-risk patients. Rarely, Metformin can cause a life-threatening condition called lactic acidosis. The symptoms of lactic acidosis appear quickly and suddenly. You should seek immediate medical care if you experience extreme tiredness, weakness, nausea, vomiting, stomachache, reduced appetite, shortness of breath or rapid, deep breathing, lightheadedness, dizziness, slow or fast heartbeat, skin flushing, feeling cold, and/or muscle pain. The risk of lactic acidosis is higher in people over 65 years of age, those with kidney disease, liver disease, and heart disease, and patients who have had a heart attack, stroke, or diabetic ketoacidosis in the past. 

The use of certain medications with metformin can increase the risk of lactic acidosis. Be sure to give your health care providers a complete list of medications, including prescription and non-prescription drugs, dietary supplements, vitamins, and herbal products. 

Inform your doctor if you have severe diarrhea, vomiting, fever, or serious infections. Also, tell your doctor if you are drinking very little fluid for some reason. Your metformin treatment may need to be temporarily stopped until you recover.

Before any surgery or dental procedure, tell your doctors that you take metformin. Also, tell your health care providers if you’re going to have an X-ray procedure involving a dye injection. This is especially true for people who drink large amounts of alcohol and those with liver disease or heart failure history. Your health care providers may need to stop metformin for a few days before and after the imaging.

Routine serum Vitamin B12 levels should be measured at two- to three-year intervals as the drug has been observed to cause subnormal B12 levels in certain individuals. 

What should I tell my doctor before starting metformin (metformin)?

Tell your health care professional about all your medical conditions - Metformin tablets may not be suitable for people with kidney disease and some other medical conditions.

Also, tell your doctor about all your medications, including prescription and over-the-counter medications, dietary supplements, and herbal remedies. This can help avoid serious drug interactions.

Tell your doctor if you drink alcohol on a regular basis. Binge drinking (drinking large amounts of alcohol in a short period) increases the risk of developing lactic acidosis and can lead to a dangerous drop in blood sugar levels. Ask your healthcare provider how much alcohol is safe to drink while on metformin treatment.

Be sure to tell your doctor if you have previously had an allergic reaction to metformin or any of the other ingredients in metformin.

Metformin is safe to take before and during pregnancy and while breastfeeding your baby. Please contact your doctor if you become pregnant while on metformin. Follow your doctor’s instructions on metformin use during pregnancy. Metformin can help control diabetes during pregnancy and prevent the complications of high blood sugar in both mother and baby.

What precautions should I take while on metformin?

Keep all your doctors’ and laboratory appointments. Your health care professional may order certain tests during metformin treatment to check if your kidneys are working well and assess your body’s response to the medicine.

What are metformin interactions?

Taking certain other medications with metformin can affect its efficacy. Drug interactions can also increase the risk of serious side effects and complications such as lactic acidosis. Your physician may choose a different anti-diabetic medication for you or change the dose or frequency of one or both medicines if there are known drug interactions.

Tell your doctor if you are taking the following medications

  • acetazolamide (Diamox)
  • methazolamide 
  • dichlorphenamide (Keveyis)
  • zonisamide (Zonegran)
  • topiramate (Topamax)

This list does not describe all possible metformin interactions. Give your health care provider a complete list of your medications, including prescription drugs, over-the-counter medicines, dietary supplements, and herbal remedies. Also, tell your health care provider if you smoke, drink alcohol, or use illegal drugs because some of these substances can cause serious health complications when used with metformin.

Pros & Cons

Metformin Pros and Cons

  • Metformin is a relatively inexpensive drug that is well tolerated by most patients.
  • Metformin is one of the most commonly prescribed anti-diabetic drugs in the world, and doctors have a good understanding of its benefits and risks. 
  • You can monitor your blood sugar levels to see if metformin is working. 
  • The medication can be used during pregnancy.
  • Metformin can cause nausea, vomiting, and diarrhea as side effects. These symptoms usually go away over time. You can reduce these effects by taking metformin with food.
  • There is a rare but serious risk of lactic acidosis.

Pharmacist Tips

Metformin Tips from Pharmacists

  • Taking metformin with meals can help prevent gastric side effects such as stomach pain, nausea, vomiting, bloating, and indigestion. 

  • Avoid drinking large amounts of alcohol in a short period while on metformin treatment. Binge drinking increases the risk of lactic acidosis, a potentially life-threatening complication. 

  • Tell your doctor immediately if you experience any of these rare but serious symptoms while on metformin - extreme tiredness, weakness, severe stomach pain, nausea, vomiting, reduced appetite, shortness of breath, rapid and deep breathing, dizziness, lightheadedness, abnormally fast or slow heart rate, flushed skin, feeling cold, and muscle aches. 

  • Keep all your doctors’ appointments while taking metformin. Your doctor may order some blood tests while you are on this medicine to see how well it is working as well as the medicine’s effects on your body.

Rx Savings Tips

Metformin Rx Savings Tips

Metformin is available as a generic medication. Brand name Glucophage and generic metformin contain the same medicine and are equally effective and safe. Like with most medications, generic medicine offers a better value. However, a BuzzRx Glucophage coupon can result in great savings on the brand-name drug, with the medication costing you a fraction of the retail price at a nearby pharmacy. For example, brand name Glucophage may be under $11.00 for 180 tablets of the 500-mg dose at nearby pharmacies such as Walgreens and CVS with a BuzzRx discount coupon.

Lowest Price for Metformin

Pricing based on most commonly-filled versions. Select the strength and quantity of your medication for the most accurate pricing.

Common Questions about Metformin

Is Glucophage the same as metformin?

Glucophage is the brand name of the generic drug metformin. They both contain the same active ingredient and are equally safe and effective.

What is the generic name for Glucophage?

The generic name for Glucophage is metformin or metformin hydrochloride.

How much is metformin?

With a BuzzRx discount coupon or savings card, you will end up paying under $9 for 30 tablets of the 500 mg dose of metformin.

Is metformin good for weight loss?

Metformin may help people with diabetes lose weight by decreasing their appetite.

What is the best time to take metformin?

Regular metformin tablets should be taken with or immediately after meals, two to three times a day as prescribed. The extended-release (long-acting) tablets should be taken once a day with the evening meal.

How long does it take for metformin to start working?

Regular metformin tablets should be taken with or immediately after meals, two to three times a day as prescribed. The extended-release (long-acting) tablets should be taken once a day with the evening meal.

Does metformin affect kidneys?

Metformin does not cause kidney damage. However, this medicine is cleared from the body by the kidneys via the urine. If the kidneys are not working properly, it can lead to a build-up of the drug in the body, causing serious complications such as lactic acidosis.

What is the best time to take metformin?

Metformin will not immediately lower blood sugar levels. It can take 48 hours for the effects of the medicine to develop. The full effect of the medication occurs in 4-5 days.

What is the price of metformin without insurance?

Without insurance, metformin can be as high as $116.07, but with a free BuzzRx prescription discount coupon, you could pay as low as $10.95 for 180 tablets of the 500 mg dose. Use the BuzzRx drug price look-up tool to find the lowest discounted price, and be sure to enter the correct dosage, form, and quantity for the most accurate pricing. It never hurts to ask your pharmacist to try BuzzRx when filling or refilling any of your prescriptions—whether you have insurance or not.

What is the price of metformin with insurance?

Ask your pharmacist or insurance provider for your copay price on metformin—copay amounts vary depending on the type of insurance plan you have and if there is a deductible to reach before prescription drug coverage begins.

You could save up to 80% on your prescription medication with a free BuzzRx discount coupon for metformin. When using the BuzzRx lookup tool to find the price of your medication, be sure to enter the correct dosage, form, and quantity to receive the most accurate discounted pricing. It never hurts to ask your pharmacist to try BuzzRx when filling or refilling any of your prescriptions—whether you have insurance or not.