How Long Does It Take to Lose Weight on Metformin?

One of the most studied trials on metformin and weight loss is the Diabetes Prevention Program and its long-term follow-up. On average, people who took metformin lost 2-3% of their body weight, while those on placebo stayed roughly the same.

About 29% of metformin users lost at least 5% of their starting weight after the first year, compared with 13% of those taking a placebo. Waist size also went down by about 2 cm (0.8 in). After two years, those who stayed on the medication remained 3.5% below their starting weight, while less consistent users regained most of it.

The timeline for losing weight on metformin varies from person to person. It all depends on individual factors like your diet, activity level, dosage, and how your body reacts to the medication.

Below, we’ll explain what research and real-life experiences say about how long it takes to lose weight on metformin.

How long does it take to lose weight on metformin?

Here’s the typical timeline based on research and patient experiences:

First few weeks

In the first 2-4 weeks of taking metformin, some people might see a small drop in weight, but it’s often only a couple of pounds at most. In fact, many won’t notice any change this early.

If you do lose a bit in the first month, it could be due to reduced appetite or slight water weight changes. For example, a patient on an online forum reported losing about 6 lbs within a few days of starting metformin due to a greatly reduced appetite. But this kind of quick result isn’t the norm for everyone.

Most individuals will not see dramatic weight loss in the first few weeks, since the body is still adjusting to the medication. If you experience side effects like upset stomach or diarrhea in the beginning, you might eat less and see a quick pound or two come off, but that could be temporary.

1-6 months

Many users report that by the 6-month mark, they have lost some weight and feel their clothes fitting a bit looser. In one study, overweight and obese adults took metformin for six months at doses of up to 2,500 mg per day. By the end of the study, participants lost an average of 5.8 kg (12.8 lbs), which was roughly 5.6% of their body weight.

In another study, the average weight loss with metformin monotherapy was 6.5 kg (~6% body weight) at 6 months.

On Reddit, someone shared their experience with metformin, saying the weight loss felt gradual but noticeable from the start. Early on, increasing the dose made them feel pretty sick, so they naturally ate less. Once they reached around 1500 mg/day, eating sugary or carb-heavy foods made the side effects worse, which pushed them toward healthier choices. Over about six months, they ended up losing roughly 30 lbs.

Some individuals exceed this, especially if they combine metformin with major lifestyle changes, and some lose nothing if they make no other changes.

If there’s absolutely no change by the 6-month point, it might mean metformin alone isn’t effective for weight loss in your case, and you should discuss with your doctor about other strategies.

6 months to 1 year

Over longer periods, like half a year to a full year on metformin, studies and patient data show a continuation of slow, modest weight loss. 

In the study mentioned earlier, people using metformin showed an average of about 7.3 to 7.4 kg (roughly 16 lbs) weight loss after 12 months, which was about a 6-7% reduction in body weight.

A large-scale diabetes prevention study (in people at risk for diabetes) found that after one year on metformin, 28.5% of participants had lost at least 5% of their body weight. In other words, about one in three metformin users achieved a >5% weight loss in a year, while others lost less.

Many people with type 2 diabetes on metformin see around 2-3% of their body weight lost in the first year as a side effect. To put that in perspective, if you weigh 250 lbs, 2-3% is only about 5-7.5 lbs over a year. It’s not a dramatic transformation, but it can be clinically meaningful, especially considering that even a 5% weight loss can improve health markers.

On the higher end, a 5-10% body weight reduction (which for 250 lbs would be 12-25 lbs) is possible over many months with metformin if combined with diet and exercise.

Another metformin user shared that their progress felt slow at first, with some fluctuations, especially around ovulation and their period. It took about six months, once they reached 1500 mg daily, before things became more consistent.

Over time, though, the results added up. About a year in, they had lost around 20 lbs from a starting weight of 140 and were still continuing to lose. They also noticed improvements in body fat, and cutting back on carbs seemed to make a big difference.

Beyond 1 year

If you continue taking metformin long-term, maintaining the weight you lost is possible. There is even evidence that metformin helps sustain weight loss in the long run.

In a 15-year follow-up of the Diabetes Prevention Program (DPP) study, participants who kept taking metformin maintained about 6% weight loss from their baseline on average, whereas those who had an intensive diet/exercise program initially but did not stay on metformin had about 3-4% weight loss maintained.

This suggests metformin can help keep off the weight you’ve lost. However, it’s also true that if you stop taking metformin, any weight you lost may gradually return if you haven’t made lasting lifestyle changes. Doctors often note that the weight loss effect of metformin lasts only as long as the medication is continued.

Who can use metformin for weight loss?

Metformin is not officially approved as a weight loss medication. It’s prescribed for type 2 diabetes and sometimes prediabetes. However, doctors do sometimes recommend metformin “off-label” for weight management in certain individuals.

1. Women with PCOS (Polycystic Ovary Syndrome)

PCOS is a hormonal disorder often associated with insulin resistance, weight gain, and difficulty losing weight. Metformin is frequently prescribed off-label for PCOS to help with insulin levels and even fertility. Many women with PCOS find that metformin makes it easier to lose weight when combined with diet/exercise, since it targets one of the root issues (insulin resistance) in PCOS.

If you have PCOS and are overweight, your doctor might consider metformin, especially if you have prediabetes or other metabolic risk factors. Many people with PCOS report that metformin helped break a weight-loss plateau. For example, one woman lost 12 lbs in a month after struggling to lose 7-10 lbs over the previous 7 months.

2. People who gained weight from antipsychotic medications

Another off-label use of metformin is in people who are on antipsychotic medications for conditions like schizophrenia or bipolar disorder, which often cause weight gain.

Psychiatrists sometimes add metformin to help counteract weight gain from these meds, and research supports that it can lead to modest weight loss in this scenario.

A recent study showed that metformin is the most effective drug studied so far for preventing weight gain from antipsychotics. Starting metformin at the same time as the antipsychotic reduced weight gain by about 4 kg (about 8.8 lbs) compared to not using it.

The evidence was strong enough that experts now recommend using it more routinely for this purpose. According to the new guidelines, doctors should consider starting metformin:

• • Right away, when prescribing olanzapine or clozapine

• • For patients with risk factors (like BMI over 25, cardiometabolic issues, or age 10-25) when using moderate-risk drugs (quetiapine, risperidone, paliperidone)

• • For any patient who gains more than 3% of body weight in the first year

If you’re taking any of these antipsychotic medications, speak with your healthcare provider before starting metformin. Never start, stop, or adjust any prescription medication without medical guidance.

3. Obesity with metabolic syndrome features

Some doctors might prescribe metformin to individuals with obesity who also show signs of metabolic syndrome, such as:

• • high insulin levels
  • borderline high blood sugar
  • high triglycerides
  • low HDL (“good”) cholesterol
  • increased waist circumference (abdominal fat)
  • high blood pressure

But this should be done under medical supervision, and only if other approaches haven’t achieved sufficient results.

How can you speed up weight loss with metformin?

Metformin works best for weight loss when paired with a good diet and regular exercise. Here are some practical tips to help you get the most out of metformin and speed up your weight loss in a healthy way:

Eat a balanced, portion-controlled diet

Plan for a nutritious, calorie-appropriate diet. Focus on whole foods:

• • vegetables
  • fruits
  • lean proteins (chicken, fish, beans)
  • high-fiber carbs like whole grains

Try to limit sugars and refined carbs like white bread, pastries, or sugary drinks, since they cause blood sugar spikes. Some people on metformin follow a low-carb or moderate-carb diet because it aligns well with improving insulin sensitivity. This can be effective, but it’s not absolutely required.

A simple approach is the “plate method”:

• • fill half your plate with non-starchy veggies (salad, broccoli, etc.)
  • a quarter with lean protein
  • a quarter with whole grains or starchy veg
  • a piece of fruit or dairy if desired

This naturally controls portions and carbs. Also, because metformin can cause B12 deficiency over time in some individuals, ensure your diet has sources of B12 (fish, dairy, eggs) or take a multivitamin as advised by your doctor. Don’t go on any extreme fad diets. Metformin is usually a long-term therapy, so you want eating habits you can maintain alongside it.

Don’t skip meals

Very low calorie intake can slow your metabolism and make weight regain more likely.

Researchers followed contestants from The Biggest Loser to see what happened to their metabolism and weight after extreme weight loss. Participants lost about 58 kg (128 lbs) on average, but their metabolism slowed by roughly 600 calories per day.

Six years later, participants regained about 41 kg (90 lbs), and their metabolism remained slow, still burning about 700 fewer calories per day than before weight loss.

Taking metformin on an empty stomach is also not advisable, as it can worsen stomach upset. Instead, aim for balanced meals at regular times.

Stay hydrated and limit alcohol

Drink plenty of water throughout the day. Sometimes thirst can be mistaken for hunger. Metformin can sometimes cause a dry mouth or a slight metallic taste, and drinking water helps with that, too.

As for alcohol, it’s best to moderate your alcohol intake while on metformin. Heavy drinking can increase the risk of lactic acidosis (a rare side effect), and it adds extra calories, which hinder weight loss. A drink on occasion is generally fine if your doctor approves, but avoid excessive alcohol, especially binge drinking.

Regular physical activity

Exercise can boost your results. Try to incorporate some form of physical activity daily. If you’re new to exercise, start with walking. Even a 20-30 minute brisk walk each day can make a difference. Over time, increase duration or intensity.

Mix in cardio or anything that gets your heart rate up, like jogging, cycling, dancing, with strength training (weight lifting or bodyweight exercises) a couple times a week. Strength training is particularly good because it builds muscle, and more muscle mass can raise your resting metabolism, meaning you burn more calories even at rest.

In 2022, researchers discovered a molecule called lac-phe, which is produced after intense exercise and helps reduce appetite.

Interestingly, they later found that metformin increases lac-phe levels too, similar to what happens after exercise. In mice, this led to reduced food intake and weight loss, and in humans, metformin users had higher lac-phe levels than non-users.

So, exercise and metformin might complement each other in appetite control. 

If you find yourself less hungry after a hard workout, that’s a bonus. Aim to gradually reach the recommended 150 minutes of moderate exercise per week, or 75 minutes of vigorous exercise, plus two strength sessions.

Choose activities you like, such as playing a sport, taking a group fitness class, swimming, or even active hobbies like gardening. The more fun and routine it feels, the more you’ll stick with it.

Track your progress

Consider keeping a simple log of your food intake and exercise, or use an app to track calories and activity. Tracking can help you stay accountable and identify patterns.

You don’t have to track obsessively, but it can be a useful tool, especially in the beginning, to ensure you’re in a calorie deficit if weight loss is the goal.

Weigh yourself maybe once a week at most. Because weight loss on metformin is slow, checking the scale too often might be discouraging. Weekly or bi-weekly weigh-ins can show the downward trend over time.

Be consistent with medication timing

Take your metformin as prescribed, at roughly the same times each day. Skipping doses can reduce its effectiveness for weight loss and blood sugar control. Follow your doctor’s instructions on gradually increasing the dose to minimize side effects.

If you often forget, set alarms or tie it with a daily routine (e.g., always with breakfast and dinner). If you’re on the extended-release version, take it with your evening meal consistently. Consistency helps keep your insulin levels and appetite effects steady day to day.

In the DPP study, the amount of weight change was strongly linked to adherence. Patients who took the medication consistently lost an average of 3.5% of their body weight, while those with low adherence had little to no change over 2 years. Weight loss and reductions in waist circumference persisted for over 10 years in the adherent group.

Deal with cravings smartly

Even though metformin can curb appetite, you might still have cravings now and then, sometimes out of habit or emotional triggers. Have healthy snack options available for those moments, like nuts, Greek yogurt, or carrot sticks with hummus, instead of high-sugar treats.

You could still gain weight if you frequently consume high-calorie junk food. So, plan for those moments. You can enjoy small portions of your favorite foods occasionally, just account for them in your daily intake.

Leverage support

Losing weight can be challenging, so get support where you can. This could be a weight loss support group, a dietitian or nutritionist, or even community forums. There are online communities of people on metformin or with PCOS/diabetes sharing tips and recipes.

Sometimes, just having a friend or family member as a workout buddy or someone to share healthy recipes with makes the journey easier.

Bottom line

Metformin typically leads to gradual weight loss. Most people notice small results after 4-8 weeks, with about 5-10 lbs lost over 3-6 months, especially when combined with diet and exercise. Results vary, some lose more, others less, and lifestyle habits matter most. Metformin is safe for long-term use and offers added metabolic benefits.

If no progress occurs after six months, consult your doctor. Overall, consistency and patience are vital to seeing steady, lasting results.

Frequently Asked Questions

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