What You Need to Know About Metformin for Weight Loss and Type 2 Diabetes


Man measuring his stomach.

Losing weight and keeping it off can be difficult. It might even be particularly stressful if you’re required to lose weight due to a health condition.

Although metformin is prescribed primarily for treating and managing type 2 diabetes, the drug has received plenty of attention for its weight loss benefits in recent years.

However, metformin is currently not FDA-approved as a weight loss drug, but doctors can prescribe it off-label to patients who are at risk of developing health conditions — like diabetes — as a result of being overweight or obese.

It is important to consider the effects metformin may have on you before taking the drug, regardless if you are using it to treat your diabetes or manage your weight.

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What is Metformin?

Metformin is a widely prescribed medication that falls into a class of drugs called biguanides — an oral group of medications used to treat type 2 diabetes.

Among other functions, metformin helps to lower blood sugar levels in people with diabetes. It can also be prescribed for:

  • Prediabetes: People who have higher than normal blood sugar levels. Insulin resistance: When the body has a poor response to insulin.
  • Gestational diabetes: Diabetes that occurs during pregnancy. Polycystic ovary syndrome (PCOS): A condition that causes enlarged ovaries with cysts on the outer edges.
  • Antipsychotic-induced weight gain: People who have experienced excessive weight gain from taking antipsychotic medications can take metformin to lose weight.

Metformin is taken orally, either as an immediate-release or extended-release tablet.

A healthcare professional will determine your dosage and frequency based on your specific needs.

How Does Metformin Work for Diabetes Care?

Metformin lowers blood glucose levels in three main ways.

Glucose production in the liver

Our livers naturally produce glucose. In people with type 2 diabetes, the liver often overproduces glucose — even if blood sugar levels are already high.

Metformin addresses this by targeting a key enzyme called hepatic gluconeogenesis, which is responsible for the overproduction of glucose in the liver.

By reducing how much glucose the liver produces, metformin helps to lower blood sugar levels.

Slowed glucose absorption

Metformin also decreases the amount of glucose absorbed from the intestines into the bloodstream.

It does this by reducing excess glucose transporters in the intestines, limiting the amount of glucose entering the blood.

By reducing glucose absorption from the intestines, metformin helps control blood sugar by preventing sugar spikes after food intake.

Increased insulin sensitivity

Insulin is a hormone that occurs naturally in our bodies and is responsible for regulating blood glucose levels.

With type 2 diabetes, the body’s cells become increasingly resistant to the effects of the insulin that is produced naturally. This results in elevated blood sugar levels.

Metformin assists in increasing the body’s sensitivity to insulin and boosting its efficiency in the cells. This helps with blood sugar control in insulin-sensitive people.

Key Point: Metformin Doesn’t Stimulate Insulin Production

Unlike other diabetes medications, metformin doesn’t stimulate the pancreas to produce more insulin to be released into the body.

Instead, it primarily works to address the underlying causes of elevated blood sugar, insulin resistance, and excessive glucose production.

How Does Metformin Cause Weight Loss?

Although there have been some studies that have noted weight loss as a result of metformin treatment, research is still limited.

One study by the Diabetes Prevention Program (DPP) — which examined long-term weight loss with metformin or lifestyle intervention — found that people with prediabetes taking metformin lost an average of four to seven pounds in the first year of the trial.

They also saw a reduction in their overall body mass index (BMI).

The Diabetes Prevention Program outcomes study determined that although weight loss is possible when taking metformin, it will likely only be a moderate reduction, with 29% of participants losing 5% of their body weight in one year.

Another study found that metformin helped morbidly obese subjects with a body mass index of greater than 30 lose moderate body fat and maintain weight loss.

There are several factors that could potentially help some people lose weight while taking metformin.

Appetite reduction

In initial research into metformin for weight loss, it was thought that lowered body weight resulted from decreased glucose levels.

Since then, studies have found that metformin promotes appetite regulation, resulting in a lower food intake and a decreased body mass index.

It is believed that metformin influences the hormones in the body involved in appetite control — such as ghrelin.

By regulating these hormones, metformin may assist in decreasing the appetite and promoting feelings of fullness, leading to reduced calorie intake and potential weight loss.

Balancing insulin and glucose

Low blood sugar can lead to food cravings, especially for high-carbohydrate and sugary foods. As metformin regulates blood sugar levels, it may prevent these cravings, potentially leading to weight loss.

Lipid metabolism

Lipid metabolism refers to the processes in the body that digest and store fats or lipids. Lipids are molecules in the body that include fats and oils.

Metformin may influence lipid metabolism by breaking down and using stored fat for energy, resulting in a reduction in body fat and, subsequently, weight loss.

Gastrointestinal side effects

Metformin is known for causing certain side effects including nausea and diarrhea.

There is reason to believe that people taking metformin may experience stomach upsets that cause them to eat less. This may lead to weight loss.

Gut health

Research suggests that people who are obese may have fewer short-chain fatty acids in their gut — which affects many aspects of our health, including weight.

Metformin is believed to increase the production of short-chain fatty acids and improve the gut microbiota, which could cause weight loss.

Key Point: Lifestyle Intervention While Taking Metformin

It’s important to know that taking metformin alone is not enough to lose weight. You will also need to adopt healthy habits such as:

  • Exercising regularly
  • Eating a healthy diet
  • Avoiding processed foods and sugar
  • Staying hydrated

Research has found that obese people who take Metformin see greater weight loss when they combine the treatment with healthy lifestyle changes.

How Much Body Weight Can You Lose with Metformin?

Since the FDA has not approved metformin for weight loss, there is no exact amount of weight you can expect to lose.

Based on the aforementioned studies, weight loss with metformin appears to occur over the course of six to 12 months. But it is possible that you will see weight loss earlier than this.

Studies have shown that people who lost weight while taking metformin continued to shed pounds for up to 15 years after they stopped using the medication.

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Potential Side Effects of Metformin

There are several side effects you may experience when you take metformin.

Gastrointestinal problems

Studies have found that gastrointestinal symptoms are the most common side effect of taking metformin.

These side effects can include:

  • Nausea
  • Vomiting
  • Diarrhea
  • Abdominal pain or discomfort
  • Bloating

As metformin affects how glucose is absorbed from the intestines, it can lead to increased levels of glucose in the gastrointestinal system, giving rise to these symptoms.

Loss of appetite

As mentioned earlier, several studies have suggested that metformin decreases appetite. The exact reason for this is not fully understood and more research is needed.

However, it is believed that this is caused by how metformin impacts the appetite-regulating hormones in the brain.

Metallic taste

Some clinical trials have found that those taking metformin may experience a metallic taste in their mouth. The drug is believed to affect the taste buds and alter the metabolism, causing a metallic taste.

Vitamin B12 deficiency

Long-term use of metformin has been found to cause a vitamin B12 deficiency in some people.

It’s unclear why this happens, but researchers believe it is because metformin interferes with how this vitamin is absorbed in the gastrointestinal tract.

Symptoms associated with a vitamin B12 deficiency include:

  • Fatigue
  • Weakness
  • Rapid breathing or shortness of breath
  • Indigestion
  • Headaches
  • Vision problems

Lactic acidosis

Although a very rare side effect, metformin may cause lactic acidosis in some people. This symptom relates to the buildup of lactic acid in the bloodstream, which can be fatal.

Lactic acidosis may occur because metformin interferes with how lactate is metabolized in the liver.

This side effect is more likely to occur in people who take too much metformin and have underlying kidney or liver conditions.

Understanding Metformin Dosages and Interactions

Metformin doses range from 500 to 2,500 milligrams per day. It is usually recommended that the medication is taken along with a meal to reduce the gastrointestinal side effects discussed above.

It is also advised that patients take metformin at the same time each day.

Remember that metformin interacts with other diabetes medications like injectable insulin. These two drugs combined may cause significantly low blood sugar, known as hypoglycemia.

Key Point: Symptoms of Hypoglycemia

If you are taking metformin and insulin for diabetes management, there is a chance you may develop very low blood sugar levels, which can be dangerous. Signs of hypoglycemia to look out for include:

  • A rapid heartbeat
  • Feeling hungry
  • Anxiety
  • Shakiness
  • Sweating
  • Dizziness
  • Drowsiness or confusion
  • Tingling sensations in the body

Medications that raise blood sugar levels, such as corticosteroids like prednisone, may prevent metformin from working effectively.

This is because the raised blood sugar levels caused by these medications can counteract the effects of metformin.

Key Point: Who Should Not Take Metformin?

Metformin carries a black box warning from the FDA which is the most serious warning a medication can get. This warning states that people with kidney disease should not take metformin as it can contribute to lactic acidosis, which can be fatal.

Also, if you have experienced any of the following conditions or if you are over the age of 65, it may not be advisable to take metformin:

  • Heart attack
  • Stroke
  • Diabetic ketoacidosis, which is extremely high blood sugar
  • Liver disease
  • Metabolic acidosis
  • Heart failure

Where Can I Learn More About Metformin for Weight Loss?

If you want to learn more about metformin and weight loss, LifeMD can help.

With LifeMD, you can consult a healthcare professional via telehealth from the comfort of your home. A licensed professional can assist you with information about metformin and weight management strategies.

You may also be interested in enrolling in the LifeMD Weight Management Program. Enrolling in the program means you’ll be working closely with licensed clinicians who will design a personalized plan to help you lose weight.

Get started today to learn more.

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This article is intended for informational purposes only and should not be considered medical advice. Consult a healthcare professional or call a doctor in the case of a medical emergency.

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