In May 2020, the Food and Drug Administration (FDA) recommended that some makers of metformin extended release remove some of their tablets from the U.S. market. This is because an unacceptable level of a probable carcinogen (cancer-causing agent) was found in some extended-release metformin tablets. If you currently take this drug, call your healthcare provider. They will advise whether you should continue to take your medication or if you need a new prescription.

Metformin is a drug that doctors use to treat type 2 diabetes. As a secondary effect, metformin might cause weight loss, although it does not have approval as a weight-loss drug.

Doctors do not usually prescribe metformin for type 1 diabetes. They can sometimes prescribe it for women with polycystic ovarian syndrome, although this use is not approved by the United States Food and Drug Administration (FDA).

Similarly, the FDA has not sanctioned metformin to help those wanting to lose weight.

In this article, we take a look at the impact metformin has on weight, as well as how the drug is used.

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Metformin has been found to lead to weight loss, though the reason for this is unclear.

People with type 2 diabetes have lost weight from taking metformin, but they are not the only ones to benefit from the drug in this way.

A study involving people who were overweight or obese and had insulin resistance showed that they lost weight while taking metformin.

While some evidence suggests that metformin does lead to weight loss, neither doctors or scientists are certain how it works.

Some researchers believe the drug reduces appetite. Others think it changes the way the body stores and uses fat.

Doctors tend to recommend certain diet and lifestyle changes alongside metformin and medications for type 2 diabetes or prediabetes. Many of these diet and lifestyle changes are also likely to lead to weight loss if the person follows the recommendations.

Metformin alone may not be enough to cause weight loss if other healthful habits are not taken up by the person using metformin.

People hoping to lose weight from metformin should also follow a nutrient-rich, low-calorie diet and exercise regularly.

People who do not adhere to other healthful habits may not lose weight on metformin.

The FDA have not approved metformin for weight loss purposes. However, some doctors will prescribe it to people who are overweight or obese and have type 2 diabetes or prediabetes.

That said, if metformin is prescribed to someone who meets these conditions, that person needs to adopt other healthful habits to support weight loss. These habits include following a nutrient-rich, low-calorie diet and getting regular exercise.

Metformin is not a quick-fix, miracle-diet drug. It is much more likely that people taking metformin will likely lose weight gradually over a long time.

It is also worth noting that people who lose weight while taking metformin may regain it if they stop taking the drug.

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A dosage plan should be decided by a doctor, to prevent unwanted side effects.

The exact dosage of metformin that people should take will vary. A person should speak to their doctor about proper dosage and report any side effects after taking the medication.

The dosage of metformin is based on someone having type 2 diabetes. How much a person takes depends on the form of the metformin and the brand. People can take some types of the drug with meals, some on their own, and others with insulin.

Some of the dosage recommendations and guidelines include:

  • For extended-release metformin and tablets, doses are between 500 and 1000 milligrams (mg) and should not exceed 2,500 mg in a day for adults.
  • For liquid forms, doses range between 5 and 8.5 milliliters (ml) for adults, and should not exceed 25 ml a day.
  • Children taking liquid forms typically use 5 ml twice a day. For most forms, children should follow doses recommended by their doctor.

If a person misses a dose of metformin, they should try to take it as soon as possible. If they are very close to their next scheduled dose, the missed dose should be skipped. It is not recommended to double up on doses of metformin.

As always, a person should speak to their doctor about proper dosage and any changes in their medication.

Metformin tablets can have some potentially dangerous side effects. The FDA have issued their most serious warning level about metformin.

Although rare, metformin may cause lactic acidosis. Lactic acidosis is an unsafe buildup of lactic acid in the blood.

A person should go to the emergency room for treatment immediately if they are taking metformin and experience any of the following symptoms:

  • weakness
  • difficulty breathing
  • tiredness
  • a sense of dizziness
  • unexplained or unusual muscle pain,
  • unusual sleepiness
  • stomach pain
  • nausea or vomiting
  • slow or irregular heartbeat

People at the most risk of developing lactic acidosis include:

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

Another serious side effect is a low blood sugar reaction. When this occurs, a person’s blood sugar drops to unsafe levels.

If a person’s blood sugar drops too low, they are at risk for:

  • seizures
  • passing out
  • brain damage
  • death

Treatment for a low blood sugar reaction needs to be started immediately to avoid some of the more serious side effects. Treatment consists of taking 15 to 20 grams (g) of glucose. This can be done in several ways, including sugary drinks and hard candies.

Symptoms of low blood sugar may include:

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

There are other, less serious side effects that metformin may cause as well. Some of the side effects a person may experience include:

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Exercising for 30 minutes, five times a week, may aid weight loss.

There are many ways to lose weight without using metformin. Most of them include making reasonable diet and lifestyle changes.

The following steps can help a person start losing weight:

  • follow a healthful diet based on eating plenty of fruits and non-starchy vegetables
  • getting at least 30 minutes of cardiovascular exercise five times a week
  • adding strength-training exercises to build muscle
  • drinking plenty of water
  • limiting sugar
  • getting enough sleep
  • keeping a food journal to track diet
  • getting support from friends and family

In some cases, weight loss surgery may be suggested for people who are obese and unable to lose weight in other ways.

When to see a doctor

Anyone who is obese or overweight and trying to lose weight should consult a doctor. A doctor can best advise how to begin losing weight safely.

Those who have tried to lose weight and have been unsuccessful should also see a doctor.

People with prediabetes or type 2 diabetes should be seeing a doctor regularly.

Metformin usage may be considered for people with type 2 diabetes to help them control their blood sugar levels.

A secondary side effect may be weight loss, which leads some to believe it may be a viable medication to use for weight loss. However, researchers are still not clear on whether or not metformin has an actual impact on weight, or if weight loss is due to lifestyle changes in people with type 2 diabetes.

People who do not have type 2 diabetes should likely seek out more traditional methods of losing weight through diet and exercise, or possibly other medications or procedures to control their weight.