Metformin is a drug that doctors use to treat type 2 diabetes and PCOS. But it can also help you lose weight. How does metformin for weight loss work? What does the research say? What are the risks and side effects? What should you consider before taking it? In this article, we will answer these questions and more.

How Metformin Lowers Blood Sugar Levels and Helps with Weight Loss

Metformin belongs to a group of drugs called biguanides. They lower blood sugar levels by:

• Reducing the amount of glucose made by the liver
• Improving the sensitivity of cells to insulin
• Insulin is a hormone that helps glucose enter the cells for energy
• People with type 2 diabetes have insulin resistance
• Their cells do not respond well to insulin and have trouble absorbing glucose
• This leads to high blood sugar levels and health problems

Metformin can help lower blood sugar levels and prevent or delay diabetes complications. These include heart disease, kidney damage, nerve damage, and eye damage. It can also reduce the risk of developing type 2 diabetes in people who have prediabetes or are at high risk.

Metformin can also help some people lose weight by reducing appetite, increasing fat burning, and changing the way the body stores and uses fat. We will explain how metformin for weight loss works in the next section.

How Metformin Reduces Appetite and Fat Storage

The exact way that metformin causes weight loss is not clear. But there are some possible reasons:

• Metformin may suppress appetite by affecting the gut bacteria
• The gut bacteria are the microorganisms that live in the digestive tract
• They may influence hunger and fullness signals
• Some studies have shown that metformin can change the gut bacteria’s composition and diversity
• Metformin may also affect the hormones that regulate appetite
• These include GLP-1, PYY, and ghrelin
• GLP-1 and PYY are hormones that make you feel full after eating
• Ghrelin is a hormone that makes you feel hungry before eating
• Metformin may increase GLP-1 and PYY and decrease ghrelin
• This may reduce hunger and food intake
• Metformin may also change how the body stores and uses fat
• Some studies have suggested that metformin can activate an enzyme called AMPK
• AMPK regulates energy metabolism and fat oxidation
• AMPK is also activated by fasting and exercise, which promote weight loss
• By activating AMPK, metformin may increase fat burning and decrease fat storage

The Evidence for Metformin for Weight Loss

Metformin is not approved by the FDA as a weight loss drug. However, some doctors may prescribe it off-label for this purpose. The evidence for metformin’s effectiveness for weight loss is mixed. However, some studies have shown promising results.

For example, a 2018 review of 12 trials with 1,151 participants found that metformin significantly decreased BMI in adolescents and adults who were overweight or obese without diabetes. The average weight loss with metformin was 3.6 kg (7.9 lbs) compared with 1.4 kg (3 lbs) with placebo.

Another study published in 2023 compared metformin with semaglutide, a new drug that mimics a hunger-regulating hormone called GLP-1. The study involved 1,961 adults with obesity who received either metformin, semaglutide, or placebo for 68 weeks. The results showed that semaglutide was more effective than metformin for weight loss. But both drugs were better than placebo. The average weight loss with semaglutide was 14.9% of body weight, compared with 6% with metformin and 2.4% with placebo.

The table below summarizes the main findings of these two studies:

Study	Drug	Duration	Participants	Average Weight Loss
2018 review	Metformin	6 to 48 weeks	Adolescents and adults who were overweight or obese without diabetes	3.6 kg (7.9 lbs)
2023 study	Metformin	68 weeks	Adults with obesity	6% of body weight
2023 study	Semaglutide	68 weeks	Adults with obesity	14.9% of body weight

The Risks and Side Effects of Metformin for Weight Loss

Metformin is generally safe and well-tolerated. However, it may cause some side effects, especially at the beginning or when increasing the dose. The most common side effects are:

• Nausea
• Vomiting
• Diarrhea
• Bloating
• Gas
• Abdominal pain

These side effects usually go away after a few weeks of taking the drug.

Metformin may also lower vitamin B12 levels in some people. This can cause anemia or nerve damage if not treated. Therefore, it is recommended to check vitamin B12 levels regularly and take supplements if needed.

A rare but serious side effect of metformin is lactic acidosis. This is a condition where too much lactic acid builds up in the blood due to low oxygen delivery to the tissues. This can cause:

• Muscle pain
• Weakness
• Breathing problems
• Irregular heartbeat
• Confusion

Lactic acidosis is more likely to occur in people who have:

• Kidney problems
• Liver problems
• Heart failure
• Alcohol abuse

If you experience any of these symptoms, you should seek medical attention immediately.

Who Should and Should Not Take Metformin for Weight Loss

Metformin is not a magic pill that will make you lose weight without any effort. You still need to follow a healthy diet and exercise regularly to achieve the best results. You should also consult your doctor before taking metformin. It may not be suitable for everyone and may interact with other drugs.

Some factors that may affect your eligibility for metformin include:

• Your blood sugar levels. Metformin is mainly used to treat type 2 diabetes or prediabetes. But it may also be prescribed to people who are overweight or obese without diabetes. However, if your blood sugar levels are too low or too high, you may not be able to take metformin safely.
• Your kidney functions. Metformin is excreted by the kidneys. So if your kidney function is impaired, you may have a higher risk of lactic acidosis or other complications. Your doctor will check your kidney function before prescribing metformin and adjust the dose accordingly.
• Your liver functions. Metformin may also affect the liver, which is involved in glucose production and metabolism. If you have liver problems, such as cirrhosis or hepatitis, you may not be able to take metformin safely.
• Your alcohol intake. Alcohol can increase the risk of lactic acidosis and liver damage when taken with metformin. Therefore, you should limit or avoid alcohol consumption while taking metformin.
• Your pregnancy or breastfeeding status. Metformin is not recommended for pregnant or breastfeeding women. It may cross the placenta or pass into breast milk and affect the baby’s growth and development.

Conclusion

Metformin for weight loss is a drug that can help lower blood sugar levels in people with type 2 diabetes or prediabetes. It can also help some people lose weight by reducing appetite, increasing fat burning, and changing the way the body stores and uses fat. However, metformin for weight loss is not a miracle drug that will make you lose weight without any effort. You still need to follow a healthy diet and exercise regularly to achieve the best results. You should also consult your doctor before taking metformin, as it may not be suitable for everyone and may cause some side effects or interactions with other drugs.

FAQs

• What is metformin and how does it work? Metformin is a drug that doctors use to treat type 2 diabetes and PCOS. It lowers blood sugar levels by reducing the amount of glucose made by the liver and improving the sensitivity of cells to insulin.
• Can metformin help you lose weight? Metformin may help some people lose weight by reducing appetite, increasing fat burning, and changing the way the body stores and uses fat. However, metformin is not a magic pill that will make you lose weight without any effort. You still need to follow a healthy diet and exercise regularly to achieve the best results.
• How much weight can you lose with metformin? The amount of weight loss with metformin varies from person to person and depends on several factors, such as the dose, duration, diet, exercise, and other health conditions. Some studies have shown that metformin can lead to an average weight loss of 3.6 kg (7.9 lbs) in people who are overweight or obese without diabetes, and 6% of body weight in people with obesity.
• What is the best dose of metformin for weight loss? The best dose of metformin for weight loss depends on your individual needs and response to the drug. Your doctor will prescribe the appropriate dose for you based on your blood sugar levels, kidney function, liver function, and other factors. The usual starting dose of metformin is 500 mg twice a day or 850 mg once a day, taken with meals. Your doctor may increase the dose gradually until you reach the maximum dose of 2,000 mg per day.
• What are the side effects of metformin for weight loss? Metformin can cause some side effects, especially when starting or increasing the dose. The most common side effects are gastrointestinal, such as nausea, vomiting, diarrhea, bloating, gas, and abdominal pain. These side effects usually go away after a few weeks of taking the drug. Metformin may also lower vitamin B12 levels in some people, which can cause anemia or nerve damage if not treated. A rare but serious side effect of metformin is lactic acidosis, a condition where too much lactic acid builds up in the blood due to low oxygen delivery to the tissues. This can cause symptoms such as muscle pain, weakness, breathing problems, irregular heartbeat, and confusion. If you experience any of these symptoms, you should seek medical attention immediately.