Does Metformin Support Weight Loss? The Full Picture
DiabetesType 2 Diabetes

Does Metformin Support Weight Loss? The Full Picture

Does Metformin Support Weight Loss? The Full Picture
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Updated on November 6, 2025
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Metformin is approved by the U.S. Food and Drug Administration (FDA) for the treatment of type 2 diabetes. Weight loss is recognized as a side effect of metformin, and many people who treat their diabetes with metformin can lose 2 to 3 percent of their body weight within one year of starting treatment.

But as a weight loss therapy, specifically, metformin isn’t currently approved by the FDA. Studies do, however, link the drug to weight reduction in people living both with and without diabetes.

Here’s what you need to know about metformin and weight loss.

Diabetes 101: What Is Metformin?

Diabetes 101: What Is Metformin?

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How Does Metformin Cause Weight Loss?

The relationship between metformin and weight is unclear, but several theories provide possible explanations for weight fluctuations.

It Reduces Appetite, Possibly by Increasing Appetite-Suppressing Hormones

Research suggests that patients on metformin may have higher levels of an “anti-hunger” molecule called lac-phe in their bodies. It causes appetite loss and, in turn, weight loss from eating less at mealtimes.

Metformin also boosts levels of the appetite-suppressing molecules GLP-1 and PYY, which signal fullness.

It Limits Liver Glucose Production and Improves Insulin Sensitivity

Metformin is the most common treatment for type 2 diabetes because it mainly acts by lowering the amount of glucose released by the liver, according to Minisha Sood, MD, a board-certified endocrinologist in New York City.

Dr. Sood adds that this helps insulin to work more efficiently.

“When insulin works better — and insulin sensitivity improves — a person’s insulin levels are lower than they would be otherwise,” she says, adding that this is key for weight loss and weight management.

It May Trigger Changes in the Gut Microbiome

Research suggests metformin may also lead to weight loss as a result of shifts in the gut microbiome and reversal of metabolic changes that usually happen with age. Its effects on the microbiome are still being explored, but it may boost dozens of bacteria that regulate levels of inflammation, metabolism, and glucose production.

Side Effects Like Nausea and Diarrhea May Curb Food Intake

The gastrointestinal side effects of metformin may directly or indirectly affect appetite.

Does Metformin Lead to Long-Term Weight Loss?

In a 15-year study, researchers found that 28.5 percent of people taking metformin had lost more than 5 percent of their body weight. But between years 6 and 15, only 6.2 percent had maintained that weight loss.

How Does Metformin Compare With Approved Weight Loss Drugs?

While diabetes patients on metformin tend to lose around 2 to 3 percent of their body weight within the first year, patients taking semaglutide drugs, such as Ozempic and Wegovy, often reported losing 15 percent or more.

Tirzepatide (Zepbound) is another weight loss–approved medication with studies suggesting weight reduction ranging from 5 percent to as high as 25 percent.

Do Doctors Ever Prescribe Metformin for Weight Loss?

Metformin is sometimes prescribed off-label for weight management in people without type 2 diabetes. “Off-label” means an FDA-approved drug is prescribed to treat a condition that it was not originally approved for.

One common off-label use for metformin is addressing weight gain associated with antipsychotic medication.

Metformin Side Effects and Interactions

Whether you’re taking metformin for type 2 diabetes or off-label for a different reason, potential side effects overlap, according to Sood.

Potential side effects include:

  • Diarrhea
  • Nausea
  • Stomach pain
  • Indigestion
  • Gas
  • Constipation
  • Headaches
  • Muscle pain
  • Rash
Less-common side effects include:

  • Chest discomfort
  • Weakness
  • Hypoglycemia
  • Nasal symptoms (rhinitis)
  • Excessive sweating (diaphoresis)
Prolonged use of metformin may also cause a decrease in vitamin B12 levels.

Talk with your doctor if you are taking metformin and begin to experience any side effects.

Metformin Interactions

Among people taking metformin, specific drug interactions can raise the risk of lactic acidosis, which causes a buildup of lactic acid in the bloodstream, leading to a potentially dangerous drop in blood pH. The following drugs can cause this interaction if taken with metformin.

  • bupropion
  • carbonic anhydrase inhibitors
  • cephalexin
  • cimetidine
  • dolutegravir
  • ethanol
  • glycopyrrolate
  • iodinated contrast agents
  • lamotrigine
  • ranolazine
  • topiramate
Other drugs, when interacting with metformin, may enhance the hypoglycemic effect of metformin. Among other antidiabetic agents, these include:

  • androgens
  • alpha-lipoic acid
  • salicylates
  • selective serotonin reuptake inhibitors
  • quinolones
  • prothionamide
  • pegvisomant

Talk with your doctor about other treatments you’re currently taking before starting metformin.

Who Can Take Metformin?

Metformin is FDA-approved to treat type 2 diabetes in adults, as well as in children 10 and older.

Who Shouldn’t Take Metformin?

Before taking metformin, tell your doctor or pharmacist if you’re:

  • Allergic to metformin or any of the ingredients in liquid or tablets
  • Taking other prescription and nonprescription medications, including vitamins, supplements and herbal products
  • Had or have lower levels of B12
  • Pregnant, plan to become pregnant, or breastfeeding
  • Eating less or exercising more than normal, which can affect blood sugar levels
  • Older than 65 and have experienced a heart attack, stroke, diabetic ketoacidosis, a coma, or heart or liver disease

Also tell your doctor before taking metformin if you:

  • Regularly drink alcohol
  • Have kidney disease

The Takeaway

  • Metformin is FDA-approved for the treatment of type 2 diabetes.
  • Weight loss is considered a side effect of metformin, and it’s sometimes prescribed off-label for weight management purposes in specific instances.
  • Other treatments approved for weight loss by the FDA may be more effective than metformin.

FAQ

What is metformin?
Metformin is an FDA-approved medication for the treatment of type 2 diabetes.
Weight loss is considered a side effect of metformin. Other side effects include gastrointestinal issues, headache, and muscle pain, among others.
Diabetes patients on metformin tend to lose around 2 to 3 percent of their body weight within the first year of starting treatment.
Metformin is only approved to treat type 2 diabetes. Doctors don’t usually prescribe it for weight loss exclusively. But it can be prescribed off-label, and is sometimes used to manage weight gain caused by antipsychotic medications.

Resources We Trust

Additional reporting by Leslie Barrie.

EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Resources
  1. Corcoran C et al. Metformin. StatPearls. August 17, 2023.
  2. Weight Loss Caused by Common Diabetes Drug Tied to "Anti-hunger" Molecule in Study. Stanford Medicine. March 18, 2024.
  3. Yerevanian A et al. Metformin: Mechanisms in Human Obesity and Weight Loss. Current Obesity Reports. January 2019.
  4. Wang Y et al. Advances in the Mechanism of Metformin with Wide-Ranging Effects on Regulation of the Intestinal Microbiota. Frontiers in Microbiology. May 24, 2024.
  5. Jones LA et al. Alterations in GLP-1 and PYY Release with Aging and Body Mass in the Human Gut. Molecular and Cellular Endocrinology. December, 2023.
  6. Apolzan JW et al. Long-term Weight Loss with Metformin or Lifestyle Intervention in the Diabetes Prevention Program Outcomes Study. Annals of Internal Medicine. November 2019.
  7. Jastreboff AM et al. Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine. June 4, 2022.
  8. Understanding Unapproved Use of Approved Drugs "Off Label". U.S. Food and Drug Administration. February 5, 2018.
  9. Metformin. MedlinePlus. February 2024.
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Adam Gilden, MD, MSCE

Medical Reviewer
Diplomate of American Board of Obesity Medicine Foundation

Adam Gilden, MD, MSCE, is an associate director of the Obesity Medicine Fellowship at University of Colorado School of Medicine and associate director of the Colorado University Medicine Weight Management and Wellness Clinic in Aurora. Dr. Gilden works in a multidisciplinary academic center with other physicians, nurse practitioners, registered dietitians, and a psychologist, and collaborates closely with bariatric surgeons.

Gilden is very involved in education in obesity medicine, lecturing in one of the obesity medicine board review courses and serving as the lead author on the Annals of Internal Medicine article "In the Clinic" on obesity.

He lives in Denver, where he enjoys spending time with family, and playing tennis.

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Valencia Higuera

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Valencia Higuera is a writer and digital creator from Chesapeake, Virginia. As a personal finance and health junkie, she enjoys all things related to budgeting, saving money, fitness, and healthy living. In addition to Everyday Health, Higuera has written for various publications, including Healthline, GOBankingRates, MyBankTracker, and The Mortgage Reports.
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