Metformin is used to treat type 2 diabetes and prediabetes and is used off-label for many reasons, including weight loss, antiaging, and treating polycystic ovary syndrome. It has a very good safety profile and reduces blood sugar levels. However, one of its most common side effects is diarrhea.
Metformin does not work in the same way as insulin. It lowers glucose production in the liver, decreases glucose absorption from the intestines, and increases insulin sensitivity.1 Unlike other diabetes medications, metformin does not cause hypoglycemia (low blood sugar). Metformin takes a few days to start working.
Diarrhea is having loose or watery stools at least three or more times per day.
After you chew and swallow food, it passes through the esophagus to the stomach, where the digestive process begins. Stomach muscles contract and mechanically begin to break down food. Gastric enzymes and hydrochloric begin chemical digestion. Food continues to be digested in the small intestine.
After food is digested, carbohydrates, proteins, and fats are absorbed through the intestinal walls into the bloodstream. This process occurs in the small intestine. Much of the water and fluids used for digestion are reabsorbed in the large intestine. If the intestinal contents move through the intestines too quickly, there is not enough time to absorb all the liquids, and you get loose, watery stools or diarrhea.
Almost 75% of people with diabetes report having diarrhea, and metformin can worsen it. High blood sugar can damage the lining of blood vessels, reducing blood supply to nerves and causing damage. While diabetic neuropathy is more common in the legs and feet, it can occur in the gastrointestinal tract.
Nerve damage in the stomach and intestines can cause:
If you take metformin to treat type 2 diabetes, diarrhea may result from diabetes and be made worse by taking metformin. However, diarrhea associated with diabetes is much more common in type 1 diabetes than in type 2.3
Diarrhea is a known side effect of metformin. About 25% of people have gastrointestinal side effects when they take metformin. About 5% of people are unable to take metformin at all.4
Metformin acts in the gut, in addition to the liver. Changes in gut motility can be a result of the following:5
Why metformin causes diarrhea is unclear. But it is likely due to drug accumulation in the gut. Some people find that the delayed release form of metformin causes fewer side effects than the immediate release.6 Talk to your doctor to see if changing to an extended or delayed release metformin may help your symptoms.
Some people have problems with loose stool the entire time they take metformin, while others only have it for the first few days.
Talk to your doctor before taking any medications to verify that there are no known side effects associated with them that may be worse due to your health conditions or that they do not adversely interact with any medications you are taking.
Imodium and other anti-diarrheal medications are intended for short-term use. Your doctor may suggest trying an anti-diarrheal medication when first taking metformin. If you continue to have diarrhea, talk to your doctor about a long-term plan to control your diarrhea, such as:6
If your diarrhea persists, talk to your doctor to see whether medication changes are appropriate. Call your doctor if you have vomiting, nausea, abdominal or rectal pain, bloody or tarry stools, or stool that contains pus.
Metformin, like all medications, has side effects, which can vary between users. Your symptoms may also improve after your body adapts to metformin use. If you have questions about metformin or are interested in getting metformin for weight loss, talk to an Invigor Medical specialist today.
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While we strive to always provide accurate, current, and safe advice in all of our articles and guides, it’s important to stress that they are no substitute for medical advice from a doctor or healthcare provider. You should always consult a practicing professional who can diagnose your specific case. The content we’ve included in this guide is merely meant to be informational and does not constitute medical advice.