You’re in a fitting room working through the assortment of jeans you brought in. You’ve got the size you think you are, the size you probably are (reality check), and the size you hope to be soon, if you can just make it there!

Then you hear about a drug called metformin that may aid in weight loss. Sure, it might sound odd to consider taking a medication usually prescribed for type 2 diabetes just to lose some weight. But does it work, and is it a good option for you?

The short answer is maybe.

Let’s look at how metformin, a drug prescribed to manage blood sugar levels, has earned this reputation.

Metformin can help some people lose weight, but the reasons aren’t exactly clear. Some researchers believe the drug reduces appetite, while others theorize it changes the way the body stores and uses fat.

But researchers agree that metformin is not a quick fix. According to one long-term study, weight loss from metformin happened gradually over one to two years. And the average amount of weight lost in that time ranged from 4 to 7 pounds.

Lifestyle plays a big role as well. Taking the drug without practicing other healthy habits may not lead to weight loss.

People who exercise and follow a healthy diet while taking metformin tend to lose the most weight. This is because metformin is thought to increase the number of calories burned during exercise. So if you aren’t exercising, you likely won’t reap this benefit.

Continued use is also important, as weight loss may last only as long as you’re taking the medication. That means if you stop taking metformin, there’s a good chance you’ll return to your original weight. And even while you’re still taking the drug, you may slowly gain back any weight you’ve lost.

Bottom line

Metformin is not a magic diet pill. It has been shown to reduce weight in some people but not others. Regardless, one benefit of metformin is that even if it doesn’t cause weight loss, it also doesn’t cause weight gain, which is not true for many medications used to treat type 2 diabetes.

Someone who has type 2 diabetes or prediabetes and has a higher body weight may be prescribed metformin to help manage their diabetes or lower their overall risk of developing it. Metformin isn’t usually prescribed for type 1 diabetes.

What if I don’t have diabetes?

A doctor may prescribe metformin for weight loss even if a patient doesn’t have diabetes or prediabetes.

This type of use would be classified as “off-label,” meaning the FDA has not specifically approved it. Because of this, there’s less information available about how effective metformin is for weight loss not related to diabetes.

But management of diabetes and weight loss aren’t the only reasons a doctor might prescribe metformin.

Polycystic ovary syndrome (PCOS), also known as polycystic ovarian syndrome, is a common health condition caused by an imbalance of female reproductive hormones. It affects 1 in 10 women of childbearing age.

PCOS has been linked to insulin resistance. This connection is especially common in patients who have a family history of diabetes, have higher body weights, or are not very physically active.

Over time, insulin resistance can lead to type 2 diabetes. For that reason, metformin has been proposed to help treat PCOS. Again, this would be an off-label use, as metformin has not been approved by the FDA to treat PCOS.

Use of metformin may not be the only reason a person loses weight. Weight loss can also result from accompanying conditions.

These include:

  • depression
  • stress
  • anxiety
  • chronic obstructive pulmonary disease (COPD)
  • cancer
  • AIDS
  • Parkinson’s disease
  • digestive issues like IBS or stomach infections

Other medications may also play a role. Chemotherapy drugs often result in weight loss due to reduced appetite, as do certain medications prescribed to treat ADHD (such as Adderall and Concerta).

If your doctor prescribes metformin, they will decide what dose is best for you. Usually the dosage starts small and increases gradually over a few weeks to minimize side effects.

Dosage also depends on whether the patient has type 2 diabetes and on the specific type of metformin prescribed.

Adults initially take 500 milligrams (mg) twice a day or 850 mg once a day. Dosage can be increased in increments of 500 mg per week or 850 mg every two weeks, up to 2,000 mg per day, and given in divided doses. The drug is taken orally, usually with a meal.

Always consult your doctor for the proper use and dosage of medications.

As with any medication, it’s important to consider the associated risks.

The current drug labeling by the FDA strongly recommends against metformin use in people who have abnormal kidney function.

For these patients, the use of metformin can increase the risk of developing lactic acidosis, a serious and potentially fatal condition. Lactic acidosis is a result of too much lactic acid buildup in the blood.

It’s also important to know when to seek help for certain side effects. If you experience the following symptoms while taking metformin, see a doctor ASAP:

  • weakness
  • difficulty breathing
  • tiredness
  • dizziness
  • random muscle pain
  • unusual sleepiness
  • stomach pain
  • nausea or vomiting
  • slow or irregular heartbeat

People most at risk of developing lactic acidosis include:

  • those who use or abuse alcohol while taking metformin
  • those with liver problems
  • those with kidney problems

Another serious side effect is a low blood sugar reaction. When this happens, your blood sugar drops to dangerous levels. If your blood sugar drops too low, there’s a risk of seizures, fainting, brain damage, or even death.

A low blood sugar reaction needs to be treated immediately to avoid additional dangerous side effects. Treatment usually consists of taking 15 to 20 grams of glucose. This can be done in several ways, including by drinking sugary drinks or eating candies.

Some symptoms of low blood sugar include:

  • drowsiness
  • irritability
  • headache
  • weakness
  • confusion
  • shakiness
  • hunger
  • increased heart rate
  • sweating
  • dizziness

Other possible side effects include:

  • gas
  • diarrhea
  • nausea
  • heartburn
  • stomach pain

Every weight-loss journey is different, and the healthiest, most consistent route remains a combination of diet and exercise.

If you’re curious whether metformin could be a good addition for you, talk to your doctor. They can answer your questions and help find a weight loss plan that’s right for you.

Some good questions to ask are:

  • Can you recommend a diet and exercise program?
  • Would I benefit from a medication to help me lose weight?
  • What is a reasonable weight loss goal for me?
  • If I lose weight, might I stop taking some of my medications for diabetes, high cholesterol, or high blood pressure?

Diabetes-friendly diets

  • Paleolithic (Paleo) diet: The Paleo diet promotes eating whole, unprocessed animal and plant foods like meat, fish, eggs, vegetables, fruits, seeds, and nuts. It avoids processed foods, sugar, dairy, and grains.
  • Gluten-free diet: Celiac disease is more common in people with type 1 diabetes. An estimated 8 percent of people with type 1 diabetes also have celiac. The only way to manage this disease is to avoid all foods containing gluten.
  • Vegetarian or vegan diet: A six-month study of 74 people with type 2 diabetes showed that vegetarian diets were nearly twice as effective as low-calorie diets at reducing body weight.
  • Mediterranean diet: This diet is based on foods traditionally eaten in countries like Italy and Greece. The cuisine is heavy on veggies, fruits, nuts, seeds, potatoes, whole grains, herbs, spices, seafood, and extra-virgin olive oil.
  • DASH diet: “DASH” stands for Dietary Approaches to Stop Hypertension (aka high blood pressure). The DASH diet encourages you to replace the sodium in your diet with a variety of nutrient-rich foods that help lower blood pressure.

Since metformin’s main purpose is to control blood sugar levels, it should probably be limited to people with type 2 diabetes.

It’s unclear whether weight loss experienced while taking metformin is a direct result of the drug or whether it could be due to lifestyle changes, other health conditions, or other medications.

People without type 2 diabetes who wish to lose weight would likely benefit more from diet and exercise than from metformin.

Bottom Line

Whether you’re diabetic or not, diet and exercise are the healthiest, most consistent route to weight loss.