Metformin Side Effects: Managing Gastrointestinal Distress
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How to Manage Metformin Diarrhea

How to Manage Metformin Diarrhea
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Updated on July 17, 2025
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Metformin — often the first drug prescribed to new patients with type 2 diabetes, and increasingly popular when used off-label for patients with type 1 diabetes — is widely known to cause gastrointestinal (GI) distress, especially diarrhea.

 Research has found that it causes GI side effects in up to 75 percent of those who take it.

For many people, the worst gastrointestinal effects begin to improve after a few weeks. In the meantime, learn how to manage unpleasant metformin side effects — and know when it’s time to talk to your care team about trying a different dose, formulation, or medication.

Diabetes 101: What Is Metformin?

Diabetes 101: What Is Metformin?

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Metformin Gastrointestinal Side Effects

The most common side effect of metformin is diarrhea, says Scott Lee, MD, medical director of the Loma Linda University Health Diabetes Treatment Center in California. Other side effects include:

  • Nausea
  • Vomiting
  • Stomachache
  • Loss of appetite
  • A metallic taste the mouth

“Most of the time, these side effects only last a few days and then improve over time,” says Avni Vora, MD, an endocrinologist at Northwestern Medicine Regional Medical Group in Orland Park, Illinois.

However, there have been reports of patients developing late-onset chronic diarrhea, even after taking metformin at the same dosage for years without issue.

Causes of Gastrointestinal Distress

Dr. Lee says it’s not entirely clear why this drug causes gastrointestinal side effects. It may be due to a combination of factors, as research shows that metformin may affect the gut in several ways, including:

  • Increasing glucose absorption in the intestines
  • Altering the gut microbiome
  • Increasing the bile acid pool within the intestines

Treatment Tips and Prevention

If you’re bothered by GI side effects from metformin, take these steps to help resolve your issues and possibly prevent them from happening again. Talk to your doctor about tweaking or switching your medication, if you decide together that it may improve your symptoms.

Try a Slower-Release Formulation of Metformin

Extended-release and delayed-release metformin formulations are designed to enter your body at a slower rate and are less likely to cause side effects. Research found that those who took long-acting metformin were less likely to experience adverse gastrointestinal events and more likely to stay on the drug.

Ask About a Lower Dosage

Lee says higher doses of metformin may result in more bothersome side effects. The highest approved dose for metformin is 2,550 milligrams, but Lee says some patients can only tolerate 1,000 milligrams in two doses split daily.

Studies show that higher doses are more effective, but it may be possible to find a sweet spot where the metformin provides the blood sugar effect needed without causing bellyaches.

Stay Hydrated

Hydration is important for people with diabetes, since not drinking enough water can result in blood sugar spikes.

 Diarrhea and vomiting can also lead to dehydration, which can make blood sugar control more challenging.
If you have either issue, replace lost fluids by drinking plenty of water, and also consider beverages that can help replace electrolytes, like zero-sugar sports drinks or bone broth.

Taking metformin with a meal and glass of water may also reduce gastrointestinal distress, preventing diarrhea from occurring in the first place.

Over-the-Counter Medications

There are many antidiarrheal drugs that are available without a prescription, including loperamide (Imodium) or bismuth subsalicylate (Pepto-Bismol).

 While these drugs can be effective, researchers caution against overuse. These meds can act as a quick fix rather than a true treatment, and it’s possible that something other than metformin — like inflammatory bowel disease — is causing your gastric distress.

Consider Switching Medicines

For many people, the worst gastrointestinal effects of metformin begin to improve over time.

 Dr. Vora says that the drug is effective, safe, and inexpensive, so it might be best to stick with it if your side effects are tolerable, in order to continue to benefit from its positive metabolic effects.
If your GI symptoms are disrupting your life, there’s growing evidence to support the use of other diabetes medications for blood sugar control and weight loss. Both GLP-1 receptor agonists, like Ozempic and Wegovy, and SGLT-2 inhibitors, like Jardiance, produce results similar to metformin and are now considered good treatment options for people with type 2 diabetes.

Both of these classes of drugs are also known to reduce the risk of cardiovascular disease and may be good options for people with heightened risks, such as high blood pressure or a family history of heart issues.

Vora notes that GLP-1 and SLGT-2 medications can be pricey, and Lee says that they may cause GI side effects that are similar to metformin.

The Takeaway

  • Metformin, a popular drug for diabetes management, often causes gastrointestinal stress. Many people who use it experience diarrhea, nausea, vomiting, and stomachaches.
  • It’s not clear why this medication causes GI problems, but it may do so because of the effect it has on the gut microbiome and intestines.
  • To prevent or minimize diarrhea symptoms, stay hydrated, take over-the-counter medicines, or talk to your doctor about taking a different dose or formulation of metformin or a different diabetes drug entirely.

Resources We Trust

EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Resources
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  3. Side Effects of Metformin. National Health Service. March 24, 2022.
  4. McCreight LJ et al. Metformin and the Gastrointestinal Tract. Diabetologia. January 16, 2016.
  5. Tan J et al. Long-Acting Metformin vs. Metformin Immediate Release in Patients With Type 2 Diabetes: A Systematic Review. Frontiers in Pharmacology. May 16, 2021.
  6. Corcoran C et al. Metformin. StatPearls. August 17, 2023.
  7. Metformin. MedlinePlus. February 15, 2024.
  8. Nagai Y et al. Effects of Increasing Metformin Dose vs Adding/Switching to Dipeptidyl Peptidase-4 Inhibitors on Glycemic Control in Patients With Type 2 Diabetes. Diabetes Therapy. February 17, 2021.
  9. Staying Hydrated When You Have Diabetes. University of Maryland Medical Center.
  10. Treatment of Diarrhea. National Institute of Diabetes and Digestive and Kidney Diseases. September 2024.
  11. Metformin (Oral Route). Mayo Clinic. July 1, 2025.
  12. Tabibian JH. Over-the-Counter and Prescription Medications. Digestive Problems Solved. April 26, 2023.
  13. Siavash M et al. Severity of Gastrointestinal Side Effects of Metformin Tablet Compared to Metformin Capsule in Type 2 Diabetes Mellitus Patients. Journal of Research in Pharmacy Practice. April-June 2017.
  14. Schroeder EB et al. Management of Type 2 Diabetes: Selecting Amongst Available Pharmacological Agents. Endotext. July 28, 2022.
  15. Wilcox T et al. Diabetic Agents, From Metformin to SGLT2 Inhibitors and GLP1 Receptor Agonists: JACC Focus Seminar. Journal of the American College of Cardiology. April 2020.
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