What People With Type 2 Diabetes Should Know About Metformin

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Metformin (brand names Fortamet, Glucophage, Glumteza, Glucophage, Glucophage XR, Riomet) is an oral medication used alone or with other medications to treat type 2 diabetes. It was FDA approved in 1994 and is also available as the combination drug rosiglitazone/metformin (Avandamet). 

Dos and Dont's

Metformin helps lower blood sugar in three ways:

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

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

Who Should Not Use Metformin

People with kidney disease or kidney failure should not take metformin. Neither should children under the age of 10. Children under the age of 17 should not use the extended-release preparation of metformin.


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.

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—must 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.

Tips and Precautions

Individuals with diabetes should follow healthy diet and exercise programs as recommended by their healthcare 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 healthcare 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).

May 28, 2020: The Food and Drug Administration (FDA) requested that manufacturers of certain formulations of metformin voluntarily withdraw the product from the market after the agency identified unacceptable levels of N-Nitrosodimethylamine (NDMA). Patients should continue taking metformin as prescribed until their health professional is able to prescribe an alternative treatment, if applicable. Stopping metformin without a replacement can pose serious health risks to patients with type 2 diabetes.

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 healthcare providers that they take it.

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Article Sources
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  2. Medline Plus Drug Information. Metformin. Updated July 15, 2019.

  3. Abdelgadir E, Ali R, Rashid F, Bashier A. Effect of Metformin on different non-diabetes related conditions, a special focus on malignant conditions: Review of literature. J Clin Med Res. 2017;9(5):388-395. doi:10.14740/jocmr2922e

  4. U.S. National Library of Medicine. Preparing for surgery when you have diabetes. Updated May 6, 2019.

Additional Reading
  • "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: Patient drug information." UpToDate Online. 2007. UpToDate.