How Long Does it Take For Metformin to Work For Weight Loss?

Mike Bohl, MD, MPH, ALM

Reviewed by Mike Bohl, MD

Written by Vanessa Gibbs

Published 04/15/2024

When you’re motivated to lose weight and taking steps to make it happen, you want results — fast. But, unfortunately, weight loss takes time, even when you’re taking something like metformin to help. 

Metformin is approved by the U.S. Food and Drug Administration (FDA) to help those with type 2 diabetes manage their blood glucose levels. Because weight loss is a “side effect” of the diabetes drug, it’s also prescribed off-label for weight loss. 

This doesn’t mean it’s a quick fix, though. So, how long does it take metformin to work for weight loss? There isn’t an exact time frame, but research shows people see weight loss after taking metformin within the first few months — but it varies from person to person.

Below, we cover more on how long it takes metformin to work, what to do if you’re not seeing results and how to take the medication for weight loss. 

There’s no set time frame for how long it takes metformin to work for weight loss. While research shows people notice weight loss and a reduction in BMI around the three-to-six-month mark, weight loss could start sooner than this and can vary from person to person.

For example, a 2017 study looked at 73 women with obesity who either took 1000mg of metformin or 360mg of orlistat — another weight loss medication — for three months. Although the group taking orlistat lost more weight, metformin was still found to be effective within the relatively short study period. 

Those taking metformin lost weight and had a reduction in their body mass index (BMI) and waist size — all within three months. 

Another study, this time from 2013, looked at 199 people without diabetes with a BMI of 27 or higher. Out of this group, 154 participants took metformin daily for six months. They had a mean weight loss of about 13 pounds by the end of the six-month period. 

By six months appears to be the sweet spot. 

A 2020 meta-analysis backs this up. It looked at 21 studies on metformin treatment for those with overweight and obesity. In total, the meta-analysis included more than 1,000 participants with a baseline BMI from 26 to 41. Studies ranged from three months to 32 months.

The researchers concluded that metformin treatment caused a “modest reduction in BMI.”  The BMI of participants with simple obesity — that is, obesity without an underlying medical cause — reduced by 1.3 units. In those with type 2 diabetes obesity, BMI decreased by 1 unit. 

The key takeaway in regards to timing? There was a reduction in BMI even in studies that were shorter than six months. But six-month-long studies showed the best results — after six months of treatment, BMI did not decrease significantly, and some regained weight at 12 months. It’s also worth noting that the researchers in this meta-analysis noted that research on metformin, treatment duration and expected results are still developing.

Beyond weight loss, you may notice other metformin benefits much sooner. 

A 2006 study on people with type 2 diabetes found fasting plasma glucose levels (the amount of sugar in your blood after fasting) were reduced by the first week of treatment. Levels kept dropping until week eight where they stabilized until the end of the 12-week experiment. 

How Long Does It Take Metformin to Start Working in Your Body?

It takes 1.5 hours for metformin to start working in your body once it’s been absorbed, and it may take about three hours to start working after you take it. 

But, of course, that doesn’t mean you’ll start losing weight the same day. It can take a little while for metformin to change the numbers on the scale. Weight loss is a slow-and-steady game. 

How does metformin help you lose weight exactly? It’s not fully understood how metformin works for weight loss, but it can help lower blood sugar levels and suppress your appetite, helping you eat fewer calories. 

Check out our blog on metformin weight loss for the nitty-gritty details. 

How quickly you lose weight on metformin will all depend on your body. While research shows people lost weight after taking metformin for three to six months, that doesn’t mean they didn’t start losing weight before this point. 

We all react differently to medication. Plus, your diet and exercise habits can make a difference in how quickly you lose weight on metformin, too. 

Don’t be afraid to ask your provider when they think you can expect to notice some changes. 

Prescribed online

Weight loss treatment that puts you first

You can’t necessarily speed up weight loss on metformin. Sticking to your metformin prescription and any lifestyle changes your healthcare provider recommends — things like exercising consistently, getting proper rest and eating a healthy diet — can help make the treatment more effective, but you can’t rush the process. 

As corny as it sounds, weight loss is a marathon, not a sprint, and everyone’s weight loss journey will look different. It’s something that takes time, patience and precaution.

It’s also worth noting that metformin alone has been shown to lead to modest weight loss. It can be taken alongside other prescription medications, however, so your doctor may create a personalized treatment plan that’s more effective for weight loss for you than metformin alone.

If you find metformin isn’t working for weight loss, the best course of action is to speak to your prescribing medical provider. They can assess your dose and determine whether you need to increase it,or they may recommend a different medication altogether. 

Your doctor might also want to discuss your diet and exercise habits and whether you need to make any tweaks there, or whether you simply just need a little more time on metformin and your current weight loss plan to notice the changes. 

Don’t panic if metformin isn’t working. There are other ways to lose weight, including other oral medications, weight loss injections, surgery and drug-free interventions that could work better for you and your body. You’ll get there.

Your doctor can tell you how to take metformin for weight loss. There are different forms of the drug and how you take it personally may vary. 

For the extended-release tablets, for example, it’s usually recommended to take metformin once a day, at the same time each day, ideally with your evening meal.  

Depending on your dose, immediate-release tablets may be taken two or three times a day, with meals.

Tip: Taking metformin with a meal can reduce the risk of gastrointestinal upset. Check out our blog on the best time of day to take metformin for more info.

Unless instructed otherwise, you should swallow tablets whole — no crushing, cutting or chewing. 

Metformin is often prescribed alongside a healthy diet and regular exercise to aid weight loss. A healthcare provider can give you guidance on the best changes to make for your lifestyle. 

Wondering what dose of metformin for weight loss is best? There’s no clear-cut answer to that. For extended-release tablets for diabetes, a healthcare professional may prescribe a starting dose of 500mg of metformin once a day. This dose may then increase by 500mg each week, up to a maximum of 2,000mg a day. 

A healthcare provider can help work out the best dose of metformin for weight loss for you.

Look out for the common side effects of metformin, which include: 

  • Indigestion 

  • Nausea

  • Vomiting 

  • Diarrhea

  • Flatulence

  • Asthenia (feeling weak or lacking energy) 

  • Stomach pain 

  • Headache 

Metformin can also cause a vitamin B12 deficiency, which may be linked with anemia. Stopping the medication or starting vitamin B12 supplementation appears to reverse this.  

Seek medical advice if you notice any serious side effects. Lactic acidosis (a buildup of lactic acid in your blood) is a potential serious side effect of metformin. Signs of this condition include feeling dizzy, having unusual muscle pain or a slow or irregular heartbeat. You’re more at risk of lactic acidosis if you have a health condition like kidney and liver problems. 

Sounds scary, but for the most part, metformin is considered safe and people tolerate it well over years of treatment. 

There are a few groups of people who shouldn’t take metformin. Before taking metformin, let your doctor know if you have any medical conditions like kidney or liver problems or type 1 diabetes, or if you’re pregnant or breastfeeding. And share any prescription or over-the-counter medications and supplements you’re taking.

You may not have to avoid metformin altogether, but you may need a different dose of certain medications. People on sulfonylureas, for example, may need to take a lower dose if they take metformin as the combo can increase the risk of hypoglycemia (low blood sugar). 

Yes, people without diabetes can take metformin for weight loss. Metformin has been shown to be effective for weight loss even in those without diabetes. 

For example, the 2013 study we mentioned earlier studied 199 participants without diabetes with a BMI of 27 or higher. Among the 199 participants, 154 took a daily dose of up to 2,500mg of metformin for six months — the average metformin dose was 2,230mg daily. The remaining 45 participants weren’t treated with the drug. 

After six months, the metformin-taking group had a mean weight loss of about 13 pounds. Those who weren’t taking metformin experienced weight gain — almost two pounds on average.

There’s no one set metformin dosage for weight loss in people without diabetes. But this study suggests up to 2,500mg of metformin can help those with overweight and obesity lose weight, whether they have insulin resistance — like those with type 2 diabetes — or not. 

Metformin may be more effective for those who have insulin-resistance. Both groups lost weight, but the group with severe insulin resistance lost significantly more weight than insulin-sensitive participants. 

Metformin can also be useful for those with prediabetes — this is when you have high blood sugar levels, but they’re not yet high enough to diagnose type 2 diabetes. If you’re at high risk of type 2 diabetes, metformin may reduce your risk by 31% over three years. Research shows metformin can aid weight loss and support a reduction in waist circumference, while also reducing type 2 diabetes risk.

If only losing weight was as easy as flipping a switch. Unfortunately, it’s often a slow and steady process — even when drugs like metformin are involved. 

Here’s the TL;DR on metformin and weight loss:

  • It may take weeks or months to see weight loss on metformin. Research shows people lose weight after three to six months of treatment. But don’t let that put you off. Weight loss works best when it’s slow and sustainable. And everyone is different, so there’s no set time frame for metformin weight loss — or any other weight loss for that matter. 

  • Speak to your prescribing doctor if metformin isn’t working. You may need a higher dose, a different medication, a few healthy diet and exercise tweaks, or simply more time on your current weight loss plan to notice any changes. Good things take time.

  • Metformin can help you lose weight and reduce your BMI and waist circumference. And alongside weight loss, it can cut your risk of type 2 diabetes if you’re at high risk for the condition. It can also be prescribed alongside other prescription meds for a personalized solution that may work better for you and your body. 

Metformin is promising as a weight loss drug, but it’s not your only option. There are other medications out there. You can learn more about diabetes medications like Ozempic® vs. metformin, for example.  

If you’re exploring your options, there are plenty of weight loss treatments that can help you on your weight loss journey.

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  7. Corcoran, C., Jacobs, T. F., (2023, August 17). Metformin - StatPearls. NCBI.
  8. Ziqubu, K., Mazibuko-Mbeje, S. E., Mthembu, S. X. H., Mabhida, S. E., Jack, B. U., Nyambuya, T. M., Nkambule, B. B., Basson, A. K., Tiano, L., & Dludla, P. V. (2023). Anti-Obesity Effects of Metformin: A Scoping Review Evaluating the Feasibility of Brown Adipose Tissue as a Therapeutic Target. International journal of molecular sciences, 24(3), 2227.
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Hims & Hers has strict sourcing guidelines to ensure our content is accurate and current. We rely on peer-reviewed studies, academic research institutions, and medical associations. We strive to use primary sources and refrain from using tertiary references. See a mistake? Let us know at [email protected]!

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment. Learn more about our editorial standards here.

Mike Bohl, MD

Dr. Mike Bohl is a licensed physician, a Medical Advisor at Hims & Hers, and the Director of Scientific & Medical Content at a stealth biotech startup, where he is involved in pharmaceutical drug development. Prior to joining Hims & Hers, Dr. Bohl spent several years working in digital health, focusing on patient education. He has also worked in medical journalism for The Dr. Oz Show (receiving recognition for contributions from the National Academy of Television Arts and Sciences when the show won Outstanding Informative Talk Show at the 2016–2017 Daytime Emmy® Awards) and at Sharecare. He is a Medical Expert Board Member at Eat This, Not That! and a Board Member at International Veterinary Outreach.

Dr. Bohl obtained his Bachelor of Arts and Doctor of Medicine from Brown University, his Master of Public Health from Columbia University, and his Master of Liberal Arts in Extension Studies—Journalism from Harvard University. He is currently pursuing a Master of Business Administration and Master of Science in Healthcare Leadership at Cornell University. Dr. Bohl trained in internal medicine with a focus on community health at NYU Langone Health.

Dr. Bohl is Certified in Public Health by the National Board of Public Health Examiners, Medical Writer Certified by the American Medical Writers Association, a certified Editor in the Life Sciences by the Board of Editors in the Life Sciences, a Certified Personal Trainer and Certified Nutrition Coach by the National Academy of Sports Medicine, and a Board Certified Medical Affairs Specialist by the Accreditation Council for Medical Affairs. He has graduate certificates in Digital Storytelling and Marketing Management & Digital Strategy from Harvard Extension School and certificates in Business Law and Corporate Governance from Cornell Law School.

In addition to his written work, Dr. Bohl has experience creating medical segments for radio and producing patient education videos. He has also spent time conducting orthopedic and biomaterial research at Case Western Reserve University and University Hospitals of Cleveland and practicing clinically as a general practitioner on international medical aid projects with Medical Ministry International.

Dr. Bohl lives in Manhattan and enjoys biking, resistance training, sailing, scuba diving, skiing, tennis, and traveling. You can find Dr. Bohl on LinkedIn for more information.


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