Metformin is particularly effective for people with diabetes or prediabetes who have obesity and have difficulty managing their blood sugar through lifestyle changes alone.

Metformin is a widely used and well-tolerated medication for type 2 diabetes and prediabetes. Healthcare professionals often prescribe it alongside diet and exercise.

If you’re currently using metformin or considering it, it’s important to understand how this medication works, what its benefits are, and what side effects it can cause. Let’s delve into the details of metformin to better understand its role in managing type 2 diabetes.

Metformin is often the first choice for treating type 2 diabetes, especially for people who have overweight and are unable to manage their blood sugar levels through lifestyle changes alone. It’s also used to help prevent diabetes in people who have prediabetes and have a high risk of developing type 2 diabetes.

Research suggests that both intensive lifestyle changes and metformin significantly reduce diabetes risk. According to studies cited in a 2018 research review, lifestyle changes can reduce the risk by 58%, while metformin lowers it by 31%. Long-term use of metformin can reduce diabetes risk by 18% over 15 years.

Metformin is particularly effective for people who have obesity, have higher glucose levels, have a history of gestational diabetes, or are younger adults.

Is metformin used for newly diagnosed type 2 diabetes?

Metformin is often recommended as a first-line treatment for newly diagnosed type 2 diabetes, along with lifestyle changes such as diet and exercise. Starting metformin early after a diagnosis of type 2 diabetes can help regulate blood sugar levels and improve insulin sensitivity.

Who is not a candidate for metformin?

Metformin may not be suitable for you if you:

  • have unmanaged diabetes
  • have type 1 diabetes
  • have anemia or B12 deficiency
  • have a liver or kidney condition
  • have a severe infection
  • have recently received treatment for heart failure or had a heart attack
  • have severe circulation problems or breathing difficulties
  • have a history of heavy alcohol consumption
  • have had an allergic reaction to metformin or any other medication

Metformin helps regulate your blood sugar levels by:

  • reducing the amount of sugar your liver produces
  • decreasing the absorption of sugar from your intestines
  • helping your body use sugar more effectively
  • slowing down a specific enzyme in your mitochondria to reduce sugar production by your liver
  • affecting a protein called AMPK, which helps inhibit your liver’s sugar production and increases the use of fatty acids for energy

According to a 2021 review, metformin works mainly in the gut, where it can change the balance of bacteria and increase the release of certain hormones that help regulate blood sugar levels.

Unlike some other diabetes medications, metformin rarely causes low blood sugar (hypoglycemia) and doesn’t usually lead to weight gain.

For the treatment of type 2 diabetes, the recommended dosages of metformin are as follows:

  • Immediate-release oral formulation: Start with an initial dosage of either 500 milligrams (mg) once or twice daily or 850 mg once daily. The typical maintenance dosage is 850 or 1,000 mg twice daily.
  • Extended-release oral formulation: Start with an initial dosage of either 500 or 1,000 mg once daily. The maximum recommended dose for this formulation is 2,000 mg, taken either once daily or in divided doses of 1,000 mg twice daily.

What are the benefits of metformin for type 2 diabetes?

Metformin offers several benefits for type 2 diabetes, including:

  • Blood sugar regulation: Metformin helps lower your blood sugar levels by reducing glucose production in your liver and increasing insulin sensitivity.
  • Low risk of hypoglycemia: Metformin rarely causes low blood sugar levels, so it’s safer for many people, especially when used alone.
  • Affordability and availability: Metformin is widely available and typically more affordable than many other diabetes medications.
  • Cardiovascular protection: According to a 2023 review, metformin may reduce the risk of cardiovascular events in people with diabetes.
  • Weight-neutral treatment: Metformin is not associated with weight gain and may even lead to modest weight loss.
  • Other potential benefits: A 2021 review suggests that metformin may have additional benefits, such as reducing inflammation and improving lipid profiles, though further research is needed to learn more about these effects.

Metformin side effects

Metformin is generally well tolerated and has a long history of safe use. However, it does have the following possible side effects:

  • Gastrointestinal side effects: Metformin commonly causes nausea, diarrhea, and abdominal discomfort in 20–30% of people who take it. About 5% of people stop taking metformin because of severe gastrointestinal discomfort.
  • Lactic acidosis: Metformin slightly increases the risk of lactic acidosis, a rare but serious condition. While this risk is higher in people with kidney health issues, the FDA approved metformin for use in people with mild to moderate kidney impairment in 2016.
  • Vitamin B12 deficiency: Metformin can reduce vitamin B12 absorption, leading to low B12 levels. Regular testing of vitamin B12 levels is recommended for people who take metformin, and supplementation may be necessary for those with low levels.

There are several alternatives to metformin for managing type 2 diabetes:

  • Sulfonylureas stimulate insulin release from your pancreas. Examples include glipizide, glyburide, and glimepiride.
  • DPP-4 inhibitors increase insulin and decrease glucose production. Examples include sitagliptin, saxagliptin, and linagliptin.
  • SGLT-2 inhibitors promote sugar excretion through urine. Examples include canagliflozin, dapagliflozin, and empagliflozin.
  • GLP-1 receptor agonists stimulate insulin release and reduce appetite. Examples include exenatide, liraglutide, and dulaglutide.
  • Thiazolidinediones improve insulin sensitivity and reduce liver glucose production. Examples include pioglitazone and rosiglitazone.
  • Insulin therapy: Insulin injections may be necessary to manage blood sugar levels in some cases.

Metformin may have advantages for heart health compared with some other diabetes drugs.

A 2013 study compared glipizide and metformin in 304 people with type 2 diabetes and coronary artery disease. After 3 years, those who took metformin had a lower risk of major cardiovascular events than those who took glipizide. These results suggest that metformin may be more beneficial for heart health in those people.

Is Ozempic or metformin better for weight loss?

Overall, Ozempic tends to result in greater weight loss than metformin. One 2021 study found that semaglutide (the active ingredient in Ozempic) reduced body weight by about 14.9% over 68 weeks.

In contrast, metformin typically leads to a reduction of about one unit in body mass index over several months, which translates to a weight loss of 1–2 kilograms (2.2–4.4 pounds), depending on a person’s height. This amount of weight loss is considered modest.

Here are some tips for talking with your doctor about metformin:

  • Be open: Share your concerns and goals openly with your doctor. It’s also important to be honest about your lifestyle so your doctor can tailor your treatment plan to your needs.
  • Ask questions: Ask about how metformin works, what side effects it might cause, and how it can fit into your overall treatment plan. There are no silly questions!
  • Discuss alternatives: If you’re uncomfortable with metformin, you can ask about other options.
  • Follow your doctor’s advice: Stick to the prescribed dose and schedule and promptly report any side effects.

Metformin is a widely used medication for type 2 diabetes. It works by reducing the production of glucose in your liver, improving your body’s ability to use glucose, and possibly affecting your gut bacteria to help manage glucose levels.

When discussing metformin with your doctor, it’s important to be open and honest about your medical history, including any kidney or liver issues, to ensure that this medication is safe for you. Your doctor can help determine whether metformin is the right choice for you based on your individual needs and health status.