What is Metformin?

Generic metformin tablets, sold in the United Kingdom.

(Image credit: Public domain.)

Metformin is a prescription drug used primarily in the treatment of Type II diabetes. It can be used on its own or combined with other medications. In the United States, it is sold under the brand names Fortamet, Glucophage, Glumetza and Riomet.

"Metformin is very often prescribed as the first step in a diabetic's regime," said Ken Sternfeld, a New York-based pharmacist.

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Metformin aims to decrease glucose production in the liver, consequently lowering the levels of glucose in the bloodstream. It also changes the way that your blood cells react to insulin. "It makes them more sensitive to insulin," said Dr. Stephen Neabore, a primary care doctor at the Barnard Medical Center in Washington, D.C. "It makes the same amount of insulin work better. It transports the insulin to the cells in a more effective way."

Metformin is sometimes prescribed to treat polycystic ovarian syndrome (PCOS), according to Neabore. "I can't think of a time when I've seen major side effects," he said. Clinical studies by the University of Chicago have supported its efficacy. Using metformin to treat PCOS is not yet approved by the Federal Drug Administration (FDA), however. Neabore recommends talking to a doctor about the drug's potential in this category.

According to the University of Chicago Medical Center, lowering insulin levels also lowers the amount of testosterone produced, thus theoretically decreasing the symptoms of PCOS that are associated with excess testosterone. Metformin may help restore regular menstrual cycles and improve metabolism, thus possibly leading to weight loss in women with PCOS. It may also help reduce the chance of miscarriage or gestational diabetes and improve the chance of successful in-vitro fertilization (IVF), though according to the NIH, research is inconclusive on all of these topics.

Sternfeld emphasized the importance of adhering to the metformin dosage and schedule laid out by your doctor and also discussing it with your pharmacist. "Metformin is a maintenance drug and you need to take it as prescribed forever," he said. "If you don't take it at that dosage level, your sugar level will go up. There's a direct relationship between adherence to the drug and disease state. If you don't manage your sugar levels, you're not just looking at being diabetic but at being someone who has multiple blood sugar problems."

Metformin can be taken as a tablet, an extended-release oral tablet or a liquid. Extended-release tablets should be swallowed, not chewed, crushed or split. The regular tablet is taken with meals two or three times a day, the extended-release tablet is taken once a day with a meal in the evening, and the liquid is usually taken with meals once or twice a day. "Its effects can greatly depend on the time of day you take it. Patients are always advised to take it after meals to avoid stomach distress," Sternfeld said.

Doctors often start patients on low doses of metformin and gradually increase the dosage. "If you start someone on too high a dose, they may have severe diarrhea," Neabore said. Patients must carefully monitor blood sugar while taking metformin so that doctors will be able to determine how well the drug is working. The NIH stresses that patients should not stop taking metformin without consulting a doctor, even if they feel well. Metformin cannot cure diabetes, only help control it.

It is important for diabetic patients to follow a healthy eating and exercise routine as outlined by their doctor, Neabore said. "We recommend lifestyle changes as a primary intervention or at least along with medication," he said. In rare cases, serious and sustained lifestyle changes may even change the amount of metformin a patient may need in the future. "You might be able to reduce the dose or even discontinue it eventually," he said. "But lifestyle changes take some time and in the meantime it can be good to take medicines."

More serious side effects are chest pain and rash. If these side effects occur, patients should immediately consult a doctor or seek emergency treatment. Patients should talk to their doctor and pharmacist about other risks of metformin. Before beginning metformin they should talk to their pharmacist about managing side effects and about any other drugs they are currently taking to avoid bad reactions, Sternfeld said.

The research is inconclusive on whether or not metformin is safe to take during pregnancy. For example, the Mayo Clinic suggests that it is safe, while a 2008 study in the U.S. National Library of Medicine says, "is currently recommended that metformin be discontinued with the first positive pregnancy test result." Before getting a prescription, women should tell their doctors if they are pregnant, breast-feeding, or planning to become pregnant. If they get pregnant while taking metformin, a doctor should be informed immediately.

A 2017 study published in Pediatrics found that metformin might be helpful in treating the effects childhood obesity in prepubescent children. Overweight prepubescent boys who took metformin for six months saw improvement in insulin sensitivity and other inflammatory and cardiovascular-related obesity parameters. Similar results might be achieved through lifestyle changes, however. Pubescent children did not see any results.

Jessie Szalay is a contributing writer to FSR Magazine. Prior to writing for Live Science, she was an editor at Living Social. She holds an MFA in nonfiction writing from George Mason University and a bachelor's degree in sociology from Kenyon College.

What is Metformin?

How it works

Metformin & PCOS

Dosage

Side effects

Risks

Abuse and overdose

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