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What are the symptoms of lactic acidosis caused by metformin?

Medically reviewed by Leigh Ann Anderson, PharmD. Last updated on May 24, 2023.

Official answer


Signs or symptoms of lactic acidosis due to metformin may include:

  • Feeling very weak or tired
  • Unusual muscle pain or weakness
  • Unusual sleepiness or sleeping longer than usual
  • Trouble breathing
  • Stomach discomfort or pain, nausea, vomiting, diarrhea
  • Feeling cold, especially in your arms and legs
  • Feeling dizzy or lightheaded
  • Suddenly developing a slow or irregular heartbeat

Certain metformin drug interactions can also increase your risk of lactic acidosis, so be sure to tell your doctor and pharmacist about all of the prescription medicines, over-the-counter (OTC) drugs, vitamin or herbal or dietary supplements you take.

What is metformin?

Metformin is a common oral medication used in the treatment of type 2 diabetes. It is recommended in type 2 diabetes guidelines as the first-line drug treatment for newly diagnosed patients, along with diet and exercise.

Metformin helps to control blood sugar (glucose) levels and is sometimes used in combination with insulin or other medications. A brand name for metformin is Glumetza, but most people use the generic version these days.

Metformin has been available for the oral treatment of type 2 diabetes since 1995.

Why does lactic acidosis occur with Metformin?

Lactic acidosis is a build-up of lactic acid in your blood due to low oxygen levels. It can occur in people with kidney disease, heart disease, liver disease, and those who drink excessive alcohol. Other risk factors include dehydration, age over 65 years, or a past history of lactic acidosis during metformin therapy.

Lactic acidosis is a medical emergency and must be treated in a hospital. It's important you know about it, but it's also a rare side effect. This side effect is listed in the patient education sheet and Boxed Warning for metformin.

Do not take metformin if you: have severe kidney problems, are allergic to metformin HCl or have a condition called metabolic acidosis including diabetic ketoacidosis (high levels of certain acids called “ketones” in your blood or urine).

Talk to your doctor before you drink alcohol with metformin. Consuming excessive amounts of alcohol, over the short-term or long-term, may increase your risk for lactic acidosis.

This is not all the information you need to know about lactic acidosis with metformin and does not take the place of your doctor’s directions. Review the full drug information and discuss this information and any questions you have with your doctor or other health care provider.

Related questions

  • Umeda T, Minami T, Bartolomei K, et al. Metformin-Associated Lactic Acidosis: A Case Report. Drug Saf Case Rep. 2018 Feb 9;5(1):8. doi: 10.1007/s40800-018-0076-1. Accessed May 24, 2023.
  • Salpeter SR, Greyber E, Pasternak GA, et al. Risk of fatal and nonfatal lactic acidosis with metformin use in type 2 diabetes mellitus. Cochrane Database Syst Rev. 2010 Apr 14;(4):CD002967. Accessed May 24, 2023.
  • Metformin professional prescribing information. FDA. Accessed May 24, 2023 at

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