Metformin is often the first medication prescribed to people who develop type 2 diabetes because of its ability to help control blood glucose levels — that's the amount of sugar in your blood. Thanks to a growing body of evidence, we now appreciate that metformin's benefits may extend beyond that.
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Metformin for Insulin Resistance
Metformin is the most common treatment for type 2 diabetes, the form of the disease most closely related to obesity, according to The British Diabetic Association. It belongs to a class of drugs called biguanides and is available in generic form as well as brand names such as Glucophage, Fortamet, Glumetza and Riomet. Metformin can be used alone or with other medications, depending on each person's medical needs.
"Everybody with type 2 diabetes goes on metformin as soon as possible because it offers so many advantages," says Gerald Bernstein, MD, director of the diabetes management program at Friedman Diabetes Institute in New York City. "In terms of diabetes, metformin helps control blood sugar by reducing the amount of glucose absorbed from food and decreasing the levels of glucose produced by the liver." In addition, it helps the body better use insulin, he says.
These benefits may even start before you develop full-blown type 2 diabetes, he adds. Insulin resistance occurs when your insulin doesn't work as well as it should and your blood sugar levels rise. This condition is a precursor to diabetes — it's called prediabetes — and metformin may help prevent or delay the disease, according to National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).
Equally impressive are its weight-loss effects. In the NIDDK-sponsored Diabetes Prevention Program study, individuals who lost at least 5 percent of their body weight during the first year of the study were more likely to keep it off if they were in the metformin arm than were those taking a placebo or using lifestyle interventions.
A longer-term follow-up study found that six to 15 years later, those successful weight-loss participants kept off just over 6 percent of their original body weight. These findings were published in the Annals of Internal Medicine in May 2019.
Metformin starts to work within a month and tends to be more effective when it is paired with lifestyle changes, such as eating a healthy diet, maintaining a normal weight and exercising regularly, Dr. Bernstein says.
Metformin and Your Heart
A research review that looked at metformin's possible role in lengthening lifespan included studies on a variety of its benefits in addition to helping manage type 2 diabetes. The review, published in Cell Metabolism in June 2016, points out that metformin not only aids in weight loss and in keeping off that lost weight, but it also protects heart health, increases the chances of becoming pregnant for women with polycystic ovary syndrome and may help prevent some cancers.
It also has been shown to help improve cognitive function and potentially stave off dementia, the Cell Metabolism review points out. There's also some evidence, at least in animal studies, that suggests metformin may halt the aging process.
A November 2019 study in the European Heart Journal found a specific and important heart benefit. Taking metformin reversed left ventricular hypertrophy, a dangerous thickening of heart muscle present in a large number of people with cardiovascular disease. The study was done with people who did not have diabetes.
Read more: How to Lower Blood Sugar Levels Fast
All medications have side effects, and metformin is no exception. Mayo Clinic says common ones include:
- Stomach pain
- Cough or hoarseness
- Reduced appetite
- Low blood sugar
In 2016, the Food and Drug Administration issued a black box warning stating that metformin should not be taken by some people with kidney disease because it can increase the risk of developing a potentially fatal condition called lactic acidosis, when too much lactic acid builds up in the blood.
In addition, long-term metformin may reduce the absorption of vitamin B12, as an April 2016 study in The Journal of Clinical Endocrinology & Metabolism demonstrated. The study underscores the need for monitoring the blood level of this nutrient taking if you're taking the drug.
If you've started taking metformin, be sure to tell your doctor about any and all side effects you experience. There may be ways to lessen these effects and maximize the benefits.
- Cell Metabolism: “Metformin as a Tool to Target Aging”
- National Institute of Diabetes and Digestive and Kidney Diseases: “Diabetes Prevention Program"
- National Institute of Diabetes and Digestive and Kidney Diseases: “Preventing Type 2 Diabetes”
- European Heart Journal: “A Randomized Controlled Trial of Metformin on Left Ventricular Hypertrophy in Patients with Coronary Artery Disease Without Diabetes: the MET-REMODEL Trial”
- British Diabetes Association: “Metformin and Diabetes”
- National Library of Medicine: “Metformin”
- Gerald Bernstein, MD, director, diabetes management program, Friedman Diabetes Institute, New York City
- FDA: “FDA Drug Safety Communication: FDA Revises Warnings Regarding Use of the Diabetes Medicine Metformin in Certain Patients with Reduced Kidney Function”
- National Institutes of Health: “Vitamin B12”
- Annals of Internal Medicine: “Long-Term Weight Loss With Metformin or Lifestyle Intervention in the Diabetes Prevention Program Outcomes Study”
- Mayo Clinic: "Metformin (Oral Route)"
- The Journal of Clinical Endocrinology & Metabolism: "Long-Term Metformin Use and Vitamin B12 Deficiency in the Diabetes Prevention Program Outcomes Study"