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Does metformin cause weight loss?

Medically reviewed by Leigh Ann Anderson, PharmD. Last updated on Jan 31, 2025.

Official Answer by Drugs.com

Metformin, an oral type 2 diabetes medicine, may lead to a modest weight loss and does not usually lead to significant, if any, weight gain. In various clinical studies, when metformin was used alone, it led to a weight loss of 0.7 to 3.8 kg (1.5 to 8.4 lbs) in patients. Many clinicians consider metformin a "weight neutral" treatment, meaning it does not cause a significant amount of weight gain or loss.

Metformin (brand name: Fortamet, Glumetza) is approved by the FDA to be used with diet and exercise to improve glycemic (blood sugar) control in adults and pediatric patients 10 years of age and older with type 2 diabetes mellitus. It is classified as a biguanide and has been approved by the FDA since 1995.

Most studies have not seen a significant amount of weight loss with metformin when used alone, and it does not meet the weight loss levels seen in studies for Ozempic, Wegovy or Mounjaro. It also does not cause weight gain like insulin or a sulfonylurea treatment (for example: glimepiride, glipizide, glyburide).

Metformin is usually the first drug used to treat patients with type 2 diabetes. Metformin is favored over many other diabetes drugs as initial treatment because of its ability to control blood sugar levels, lack of weight gain and low blood sugar, oral formulation, and generic affordability.

Overall, the best way to lose weight while taking metformin is to adhere to a recommended diet and exercise program. It can also be used in combination with other type 2 diabetes medications, including:

Staying at a healthy weight is an important part of controlling type 2 diabetes. If you are concerned about gaining weight with your medicine, speak to your healthcare provider about drug and non-drug treatments that may help promote weight loss as well as control your blood sugar. Today, many treatments are available that not only effectively control blood sugar but can also help with significant weight loss in type 2 diabetes.

Related: How do Mounjaro, Wegovy & Ozempic compare for weight loss?

Weight loss with metformin in adults

Numerous studies looking at the use of metformin for the treatment of type 2 diabetes have reported modest weight loss when used in addition to diet and exercise.

Study 1: Metformin vs. placebo

In one study conducted by the manufacturer, metformin (dose: up to 2,550 mg/day) was compared to a placebo treatment (an inactive agent) in a study lasting 29 weeks.

Study 2: Metformin vs. glyburide

Another study done by the manufacturer evaluated weight loss between metformin, metformin combined with glyburide (an oral sulfonylurea for type 2 diabetes), and glyburide used alone.

Study 3: Metformin vs. rosiglitazone or glyburide

In a study with over 4,300 obese patients recently diagnosed with type 2 diabetes, patients were given either rosiglitazone (a thiazolidinedione agent used to treat type 2 diabetes), metformin, or glyburide (a sulfonylurea) as initial treatment.

Study 4: Metformin vs. dulaglutide (a GLP-1 agonist)

In a trial comparing metformin with dulaglutide, a glucagon-like peptide-1 (GLP-1) receptor agonist, weight loss at 26 and 52 weeks was similar to the dulaglutide 1.5 mg dose but smaller with the dulaglutide 0.75 mg dose.

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Study 5: Metformin plus sitagliptin (DPP-4 inhibitor) vs. metformin alone

Metformin is also combined with sitagliptin (brand name: Januvia), a 2 diabetes treatment in a class called dipeptidyl peptidase-4 (DPP-4) inhibitors. Brand names for the combinations of sitagliptin and metformin are Janumet or Janumet XR.

In 24-week long studies conducted by the sitagliptin manufacturer, when metformin was used alone or with sitagliptin, metformin led to a small but similar weight loss in most patients.

Learn More: Does Januvia cause weight gain or loss?

Is metformin approved for weight loss?

Metformin is not specifically approved to be used for weight loss as a stand-alone therapy, but may lead to a moderate weight loss in some people. Metformin, when used with diet and exercise, is approved by the FDA for blood sugar control in the treatment of type 2 diabetes in adults and children 10 years of age and older.

Some studies have shown that metformin can lead to weight loss when evaluated in non-diabetic individuals with obesity.

The authors concluded that metformin was an effective drug to reduce weight in a naturalistic outpatient setting in insulin sensitive and insulin resistant overweight and obese patients.

Which diabetes treatments work best for weight loss?

Examples of type 2 diabetes medicines that are associated with weight loss include:

Note: Liraglutide (Saxenda) and semaglutide (Wegovy) are approved for weight loss in people with or without type 2 diabetes. Tirzepatide (Mounjaro) has also been shown in clinical trials to be useful for weight loss; however, it is not currently approved as a weight loss drug. The manufacturer submitted approval for this use to the FDA in 2022, with a decision expected in 2023.

Type 2 diabetes medicines that tend to be weight neutral, not increasing or decreasing weight substantially, include:

This is not all the information you need to know about metformin for safe and effective use and does not take the place of your health care provider’s directions. Review the full product information and discuss this information and any questions you have with your doctor or other health care provider.

References
  • Metformin prescribing information. Drugs.com. Accessed Feb. 10, 2023 at https://www.drugs.com/pro/metformin.html
  • Kahn SE, Haffner SM, Heise MA, et al; ADOPT Study Group. Glycemic durability of rosiglitazone, metformin, or glyburide monotherapy. N Engl J Med. 2006 Dec 7;355(23):2427-43. doi: 10.1056/NEJMoa066224. Epub 2006 Dec 4. Erratum in: N Engl J Med. 2007 Mar 29;356(13):1387-8
  • Umpierrez G, Tofé Povedano S, et al. Efficacy and safety of dulaglutide monotherapy versus metformin in type 2 diabetes in a randomized controlled trial (AWARD-3). Diabetes Care. 2014 Aug;37(8):2168-76. doi: 10.2337/dc13-2759
  • Januvia Tolerability Profile. MerckConnect.com. Accessed Feb 10, 2023 at https://www.merckconnect.com/januvia/clinical-efficacy/tolerability/initial-combination-therapy/#top
  • Seifarth C, Schehler B, Schneider HJ. Effectiveness of metformin on weight loss in non-diabetic individuals with obesity. Exp Clin Endocrinol Diabetes. 2013 Jan;121(1):27-31. doi: 10.1055/s-0032-1327734
  • Wexler D (author). Up to Date. Initial management of hyperglycemia in adults with type 2 diabetes mellitus. Summary of glucose-lowering interventions (Table). https://www.uptodate.com/contents/initial-management-of-hyperglycemia-in-adults-with-type-2-diabetes-mellitus
  • Januvia [package insert]. Merck and Co. Whitehouse Station, NJ. Accessed Feb 10, 2023 at https://www.merck.com/product/usa/pi_circulars/j/januvia/januvia_pi.pdf
  • Hussain M, Atif MA, Ghafoor MB. Beneficial effects of sitagliptin and metformin in non-diabetic hypertensive and dyslipidemic patients. Pak J Pharm Sci. 2016;29(6 Suppl):2385‐2389. Accessed Feb 10, 2023 at PMID: 28167482.

Read next

Why does metformin cause diarrhea?

According to the manufacturer, about 53% of people taking metformin immediate-release tablets experienced diarrhea in one clinical study. In another study, 10% of people taking metformin extended-release tablets reported diarrhea as a side effect. Continue reading

Can you take metformin without food?

If you take metformin without food you may end up with an upset stomach, especially if you are just starting treatment. Nausea and vomiting is one of the most common side effects with metformin and can occur in over a quarter of patients. Continue reading

Does metformin lower A1C, if so how much?

When metformin is used alone as monotherapy, it lowers A1C by about 1% to 2% on average. A1C is a measure of longer-term blood sugar control. In most patients, metformin is suggested as the initial treatment for type 2 diabetes, but its glucose-lowering effect may not be adequate for all patients if used alone. Continue reading

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