Does Metformin Cause Diarrhea?

Metformin is a popular diabetes drug to help improve blood sugar control and insulin sensitivity. 

Metformin is considered a first-line treatment for type 2 diabetes, meaning it’s often prescribed as the first diabetes medication for patients diagnosed with type 2 diabetes.

Like any medication, metformin has potential side effects that can be difficult to deal with. 

Fortunately, there are ways to help reduce side effects and improve your quality of life.

This article discusses one common side effect of metformin: diarrhea. Keep reading to learn why metformin causes diarrhea, what to do if you experience this, and how to reduce this adverse side effect.

What is metformin?

Metformin is one of the most commonly prescribed medications for type 2 diabetes, and it may also be prescribed to patients with prediabetes. Metformin is the generic name most commonly prescribed, and the brand name for metformin is Glucophage.

There are two types of metformin – regular and extended-release (XR). Extended-release metformin is preferred if you experience side effects or prefer once-daily dosing with your medication.

Metformin doesn’t cause low blood sugar (hypoglycemia), which is one of its major benefits. Because it doesn’t cause low blood sugar, people with type 2 diabetes can take metformin along with other medications like sulfonylureas and injectable insulin.

While metformin is most commonly used for type 2 diabetes, it’s also used to help treat polycystic ovarian syndrome (PCOS). PCOS is a hormonal disorder in women often stemming from insulin resistance, similar to type 2 diabetes and prediabetes. 

One of the benefits of metformin is that it may support weight loss and doesn’t promote weight gain like some diabetes medications. If you’re overweight, weight loss of 5-10% of your body weight can improve your blood glucose levels and improve insulin sensitivity.

How do I take metformin?

Metformin is available in tablet form, and it’s meant to be taken one to three times daily. The typical dosage for metformin ranges from 500 milligrams to a maximum of 2,550 milligrams per day.

The extended-release version of metformin is usually taken in the morning with breakfast or dinner, while regular metformin is taken with meals, typically 2-3 times per day.

You can take metformin with or without food. However, taking metformin with food can help reduce potential side effects, which tend to be gastrointestinal-related.

You should take as many tablets of metformin as your healthcare recommends. Don’t reduce or increase your dose on your own, and don’t cut extended-release metformin tablets in half.

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Does metformin cause diarrhea?

Yes. One of the more common side effects of metformin is diarrhea. If you experience diarrhea, you’ll notice loose and watery stools that occur more often than you usually have a bowel movement.

Some people taking metformin can have the opposite problem and suffer from constipation

How common is diarrhea with metformin?

Gastrointestinal side effects like diarrhea are the most commonly reported symptoms from patients taking metformin. Up to 75% of patients taking metformin experience some sort of gastrointestinal side effect.

According to a study, around 30% of patients taking metformin experience diarrhea. Another study surveyed 360 patients with diabetes who took metformin and found that over 60% experienced diarrhea.

Why does metformin give you diarrhea?

Metformin is absorbed in your digestive system, which can alter the bacteria responsible for healthy digestion. These bacteria are your microbiome, which plays an important role in your overall health, not just your bowel patterns.

Metformin also increases bile acid concentrations in your intestines, which can alter stool consistency and lead to diarrhea. (4)

There are reasons that metformin causes diarrhea that aren’t as clear, such as genetic predisposition to medication intolerance and varying factors regarding gut health.

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5 foods that cause diarrhea with metformin

It can be helpful to avoid foods that might worsen diarrhea while taking metformin. You’ll probably be able to reintroduce these foods later as your body gets used to metformin. 

Still, it can help boost your quality of life if you can minimize the more severe side effects when you initially start taking metformin.

1) High-sugar foods

High-sugar foods not only make it harder to manage your blood sugar levels, but they might worsen diarrhea, too. Fructose is a type of sugar that might be especially problematic for causing diarrhea.

High-fructose foods (such as peaches, pears, cherries, and apples) or foods sweetened with fructose can cause your body to pull more water into your intestines, causing diarrhea.

Foods and drinks sweetened with high-fructose corn syrup are especially high in fructose, whereas fruits contain smaller fructose concentrations.

2) Caffeine

Caffeine is a stimulant that can cause the muscles in your digestive system to contract more, which speeds up digestion time. If your food doesn’t have as much time to be digested, it can result in diarrhea.

3) Fried foods

Fat takes the longest for your body to digest than protein and carbohydrates. People with delayed gastric emptying from gastroparesis (a type of diabetes complication) are especially prone to stomach upset when they eat high-fat foods.

Some people (even without gastroparesis) have issues digesting fried and fatty foods. If your body doesn’t break down fats well, they go to your colon, which may trigger increased fluid secretion and lead to loose, watery stools.

4) High-fiber foods

Fiber is good for you, but if you eat a lot of insoluble fiber you might get diarrhea. Unlike soluble fiber, insoluble fiber doesn’t absorb water. This means that insoluble fiber can speed up digestion, giving your intestines less time to soak up water during the process. 

Some foods that are sources of insoluble fiber include:

  • Whole-wheat flour
  • Wheat bran
  • Nuts
  • Beans and vegetables, such as cauliflower, green beans, and potatoes

5) High FODMAP foods

FODMAPs are a type of carbohydrate that can be poorly digested and lead to stomach discomfort. FODMAPs stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols.

A low FODMAP diet is very restrictive and isn’t meant to be followed for a long time. However, it can be helpful to experiment and reduce your intake of high FODMAP foods to determine if you’re sensitive to any of them. 

For instance, you might find that high lactose foods trigger stomach discomfort and diarrhea, but gluten doesn’t.

What to do if metformin gives you diarrhea?

If you start taking metformin and notice diarrhea, know that it’s normal as your body gets used to the new medication. Your diarrhea will likely improve over the first few weeks of taking it.

If your diarrhea is severe and causes dehydration, extreme weight loss, or is otherwise impacting your quality of life, you should contact your healthcare provider for medical advice. 

You might be able to temporarily reduce your dose and gradually increase it, switch to extended-release metformin (which can reduce side effects), or switch to another diabetes medication.

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How to reduce metformin diarrhea

It’s impossible to predict who will experience significant side effects from taking metformin. If you do experience diarrhea while taking metformin, there are things you can do to help reduce the side effects and improve your quality of life.

Take metformin with meals

Take metformin with your larger meal(s) to help reduce side effects. Taking metformin on an empty stomach can cause more notable side effects.

Avoid diarrhea trigger foods

As mentioned earlier, try to avoid common foods that can worsen your diarrhea. This includes caffeinated beverages like coffee and certain high-fiber foods.

Stay hydrated

Diarrhea can quickly dehydrate you, so be sure to push fluids if you’re experiencing diarrhea. Water, juice, and broth are good ways to replace lost fluids and electrolytes from diarrhea. Avoid caffeinated drinks like soda and teas when you have diarrhea, as well as alcohol. 

Eat a soft, low-fiber diet

A soft diet can help you get some nutrients without making your digestive system work hard to digest foods like high-fiber fruits and vegetables. 

Protein foods like chicken and eggs are a good choice, as are saltine crackers, applesauce, white toast, and bananas.

Be prepared when you leave the house

If you’re experiencing new-onset diarrhea, you might not want to plan any big trips where you’ll be away from a restroom for prolonged periods. Plan small outings where you’ll have access to a restroom as you learn how your body does in situations outside your home.

You might want to bring an extra pair of underwear in the chance of an accident. Wearing a disposable pad in your underwear can help provide an extra sense of security in case you experience stool incontinence.

Soothe the skin around your anus

Chronic diarrhea can quickly irritate the skin on and around your anus. You can help reduce the irritation by using a peri bottle to spray yourself clean with water instead of wiping with toilet paper, taking a warm bath after having a bowel movement, patting yourself dry instead of rubbing, and applying a protective cream like Vaseline or diaper rash cream.

How to avoid or reduce the risk of metformin diarrhea?

  • One good strategy to help reduce the risk of diarrhea is to increase your metformin dose gradually. For example, you might start taking one tablet once daily for a couple of weeks, then increase it to your goal dose over several more weeks.
  • Extended-release metformin tends to be better tolerated than immediate-release tablets, so you can ask your healthcare provider if you can try that if you’re experiencing diarrhea or are prone to diarrhea.
  • If you skip a metformin dose, don’t double up with your next dose since that might cause more side effects. If you miss a dose, just take your next dose as prescribed.

Can you take anti-diarrhea medicine while taking metformin?

Anti-diarrheal medications can help ease diarrhea symptoms as your body gets used to taking metformin.

You shouldn’t take anti-diarrheal medications for an extended time. If you use anti-diarrheal medications regularly, you should discuss ways to reduce your chronic diarrhea with your healthcare provider.

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Will metformin diarrhea go away?

Most of the time, diarrhea from metformin goes away as your body gets used to it, the same as any side effect from a medication. 

There is a chance that your diarrhea can persist even after you’ve been taking it for a long time. If that’s the case, you can discuss other potential metformin alternatives and stopping metformin with your healthcare provider.

What other side effects does metformin cause?

Besides diarrhea, some of the other common side effects of metformin include:

  • Heartburn
  • Stomach pain
  • Nausea or vomiting
  • Bloating
  • Gas
  • Constipation
  • Weight loss
  • Headache
  • Metallic taste in your mouth

Metformin can also reduce your body’s ability to absorb vitamin B12, which can cause symptoms like:

  • Weakness, tiredness, or lightheadedness
  • Heart palpitations and shortness of breath
  • Pale skin
  • A smooth tongue
  • Constipation, diarrhea, loss of appetite, or gas 
  • Nerve problems like numbness or tingling, muscle weakness, and problems walking
  • Vision loss
  • Mental problems like depression, memory loss, or behavioral changes

Very rarely a metformin overdose can lead to lactic acidosis, especially if you also have kidney problems. Symptoms of lactic acidosis include:

  • Weakness, tiredness, or lightheadedness
  • Heart palpitations and shortness of breath
  • Pale skin
  • A smooth tongue
  • Constipation, diarrhea, loss of appetite, or gas 
  • Nerve problems like numbness or tingling, muscle weakness, and problems walking
  • Vision loss
  • Mental problems like depression, memory loss, or behavioral changes

What should I avoid while taking metformin?

Besides avoiding the potential diarrhea triggers mentioned earlier, you should avoid drinking excessive amounts of alcohol while taking metformin, which may lead to low blood sugar.

Try to eat a healthy diet while on metformin, which can help you reach your blood sugar goals. 

RELATED: Medications to Avoid While Taking Metformin.


Diarrhea is a common side effect of taking metformin. Most of the time, diarrhea will go away as your body gets used to metformin. 

As your body gets used to metformin, you can adjust your diet and lifestyle to ease the impact diarrhea has on your quality of life.

If diarrhea from metformin persists beyond a couple of months or is causing severe negative symptoms, you should speak to your healthcare provider about other alternatives.

Explore More

what to eat when you have diarrhea

What Foods To Eat and Avoid When You Have Diarrhea.


  1. Karthik Subramaniam, Manoj P. Joseph, Lakshmi A. Babu; A Common Drug Causing a Common Side Effect at an Uncommon Time: Metformin-Induced Chronic Diarrhea and Weight Loss After Years of Treatment. Clin Diabetes 1 April 2021; 39 (2): 237–240. 
  2. Bouchoucha M, Uzzan B, Cohen R. Metformin and digestive disorders. Diabetes Metab. 2011. 
  3. Florez H, Luo J, Castillo-Florez S, Mitsi G, Hanna J, Tamariz L, Palacio A, Nagendran S, Hagan M. Impact of metformin-induced gastrointestinal symptoms on quality of life and adherence in patients with type 2 diabetes. Postgrad Med. 2010. 
  4. McCreight LJ, Bailey CJ, Pearson ER. Metformin and the gastrointestinal tract. Diabetologia. 2016. 

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