Metformin (Glucophage®, Fortamet®)


Metformin is a biguanide oral antihyperglycemic agent used in the treatment of type II diabetes mellitus.  Though the mechanism of action of metformin is incompletely understood, it is believed that it induces activity of AMP-activated protein kinase (AMPK) in hepatocytes, the gastrointestinal epithelium, skeletal muscle.  This leads to decreased gluconeogenesis, decreased gastrointestinal glucose absorption, and increased membrane transport of GLUT4 protein in peripheral tissues.  Recent work has shown that AMPK-independent mechanisms serve a significant role in metformin-mediated glycemic control.

Metformin is frequently prescribed along with exercise and nutritional strategies as first-line therapy for type II diabetes.  It is also sometimes given off-label in the treatment of polycystic ovary syndrome.  Common adverse effects include GI distress and rash.  In rare instances, metformin use can contribute to lactic acidosis, hepatotoxicity, or anemia, usually in the case of underlying renal or hepatic disease.

In Plain English

Metformin works in several ways to lower your blood sugar (glucose) if you have diabetes:

  • Prevents your liver from making glucose
  • Blocks your intestine from absorbing sugar that you eat
  • Helps your muscles remove glucose from blood stream


Clinical Considerations


Figure 1. Metformin clinical considerations at a glance


Evidence Basis

  • For diabetes:


Metformin In the News



  1. Wishart DS, Feunang YD, Guo AC, Lo EJ, Marcu A, Grant JR, Sajed T, Johnson D, Li C, Sayeeda Z, Assempour N, Iynkkaran I, Liu Y, Maciejewski A, Gale N, Wilson A, Chin L, Cummings R, Le D, Pon A, Knox C, Wilson M. DrugBank 5.0: a major update to the DrugBank database for 2018. Nucleic Acids Res. 2017 Nov 8. doi: 10.1093/nar/gkx1037
  2. Epocrates Rx Online [Internet database]. San Mateo (CA): Epocrates, Inc. 2003. Retrieved at Web-based; continuous content updates. Accessed 2018 May 9.
  3. “Prescription Prices, Coupons & Pharmacy Information – GoodRx.” Prescription Prices, Coupons & Pharmacy Information – GoodRx
  4. “DailyMed.” U.S. National Library of Medicine, National Institutes of Health,