Metformin: Oral Medication for Type 2 Diabetes

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Metformin for Type 2 Diabetes. Ayd?n Mutlu / Getty Images

Metformin (brand names Fortamet, Glucophage, Glumteza, Glucophage XR, Riomet) is an oral medication used alone or with other medications to treat type 2 diabetes. It is also available as the combination drug rosiglitazone/metformin (Avandamet).

What It Does

Metformin helps lower blood sugar in three ways:

  • It lowers the amount of glucose absorbed from food.
  • It lowers the amount of glucose produced by the liver.
  • It increases the body’s response to insulin.

What It Does Not Do 

Metformin does not directly lower blood sugar as insulin does. Therefore, it is not appropriate for patients with type 1 diabetes who do not produce any insulin.

History of Use

Metformin was FDA approved in 1994 for the treatment of type 2 diabetes.

Who Should Not Use 

People with type 1 (insulin-dependent) diabetes, kidney disease or kidney failure should not use it. Neither should children under the age of 10. Children under the age of 17 should not use the extended-release preparation of metformin.

Side Effects and Risks

Metformin commonly causes diarrhea if taken without food. Other side effects include stomach upset, gas and bloating, metallic taste, headache, cough and muscle pain.

If metformin is inadequate for blood sugar control, patients taking metformin can also experience high blood sugar, with symptoms of confusion, seizures, dry mouth, vomiting, sweet-smelling breath or loss of consciousness.

Anyone experiencing any of these symptoms -- or chest pain, a rash or other worrisome symptoms -- needs to seek immediate medical attention.

Rarely, metformin can cause lactic acidosis, a serious condition characterized by a buildup of lactic acid in the blood. Lactic acidosis, if untreated, can lead to organ failure and even cardiac arrest.

Symptoms include fatigue, weakness, muscle pain, shortness of breath and light-headedness.

Though it's rare when there are no other medical problems, drug overdoses or drug interactions, metformin can cause low blood sugar (hypoglycemia), which is characterized by dizziness, shakiness, sweating, confusion, or numbness or tingling around the mouth.

'Off-Label' Uses

Metformin may be used off-label to assist with weight loss, polycystic ovary syndrome, gestational diabetes and HIV lipodystrophy syndrome.


Metformin is typically taken twice a day, preferably with food. If a dose is missed, the missed pill should be taken as soon as possible, unless it is almost time for the next dose. “Doubling up” on medication in order to make up a missed dose should not be done.

Tips and Precautions

Individuals with diabetes should follow healthy diet and exercise programs as recommended by their health care providers. Meals should not be skipped and consuming alcohol should be avoided. New prescription and over-the-counter medications should not be taken without the approval of a health care professional. In addition, people with diabetes should have regular check-ups to monitor their diabetes, including blood tests to check their long-term blood sugar status (HbA1c).

Metformin should be discontinued for 48 hours before any dental or surgical procedures and before receiving iodinated contrast (i.e., with CT scans). It is important for people on metformin to tell their health care providers that they take it.


“Metformin: Drug information." UpToDate Online. 2007. UpToDate.  (subscription) 

"Metformin: Patient drug information." UpToDate Online. 2007. UpToDate.  (subscription) 

"GlaxoSmithKline Announces FDA Approval and the Launch of Avandamet® (rosiglitazone maleate and metformin HCl) as Initial Therapy in the Treatment of Type 2 Diabetes." GlaxoSmithKline. 11 Jul. 2006. GlaxoSmithKline. 

"Metformin." Healthline Drug and Medication Directory. 2006. Healthline. 

"Metformin." Medline Plus Drug Information. 1 May 2007. U.S. National Library of Medicine.

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