Keto diet diarrhea: Causes and treatments

Key takeaways

• Diarrhea and other gastrointestinal (GI) problems can happen on a keto diet due to high fat intake, changes in gut bacteria, and increased use of artificial sweeteners or sugar alcohols.
• To ease GI symptoms, consider eating more fiber, reducing dairy, staying hydrated, adding probiotics, and easing into the diet gradually.
• Talk with a healthcare professional if symptoms are severe or persist for more than a week.

A ketogenic diet, or keto diet, is a diet that is high in fat, moderate in protein, and very low in carbohydrates.

Typically, the body uses carbohydrates as an energy source. When there are insufficient carbohydrates in the body, it enters a state called ketosis. During ketosis, the body breaks down stored fat to create molecules called ketones, which it uses as fuel instead of carbohydrates.

Some people who follow a keto diet may experience diarrhea and other gastrointestinal (GI) problems as side effects. Various tips can help relieve keto diarrhea and other symptoms.

In some cases, diarrhea or GI issues may be short term while the person’s body adjusts to the new diet. However, these problems can sometimes be more long term and even last the duration of the keto diet.

Read on to learn more about how the GI diet can cause diarrhea and other GI problems, how to relieve symptoms, and when to contact a doctor.

As with any extreme dietary changes, starting on the keto diet can have an effect on a person’s stomach and intestines, causing GI problems.

Some people may continue to have GI problems throughout the keto diet. A person on a keto diet must consume a

There are a few other reasons why people on a keto diet may experience GI problems.

Microbiota

Gut microbiota refers to microorganisms in the GI tract. These mainly consist of bacteria that are important to health in many ways, including helping the body absorb nutrients. A 2021 article notes that diets high in certain fats might increase the risk of inflammation of the digestive tract, which can affect the gut environment.

However, other

High fat

To break down fat, the liver needs to produce bile. A diet high in fat requires the liver to release extra bile.

As bile is a natural laxative, an excessive amount may push waste through the digestive tract quicker than usual, leading to diarrhea.

The high fat and low carb content of the keto diet may also lead to other GI symptoms, such as nausea and bloating.

Artificial sweeteners

During a keto diet, people may consume more artificial sweeteners and sugar alcohols than usual if they try to find low carb alternatives to items that they previously consumed.

For example, they may wish to replace the sugar in tea and coffee. A 2025 review notes that excessive consumption of certain artificial sweeteners, such as sorbitol and mannitol, may cause a laxative effect, leading to diarrhea.

Diarrhea may not be the only symptom that manifests when a person begins a keto diet. People may also experience the following symptoms:

• constipation
• cramping
• abdominal bloating
• nausea
• abdominal pain
• vomiting

If someone on the keto diet is experiencing GI problems, they can try to relieve the symptoms with the following:

• Eating more fiber: Fiber can help relieve diarrhea. It is best to focus on sources of soluble fiber, such as keto-friendly fruits and flaxseed.
• Eating less dairy: As whole dairy products are high in fat, people starting on a keto diet may consume more of these than they previously did. This dietary change may reveal an intolerance to dairy, common symptoms of which are diarrhea, bloating, and gas.
• Easing into the diet: A sudden change in the diet may disrupt the GI bacteria. Easing into a keto diet by slowly reducing carbs and increasing fats may help the body adapt better.
• Staying hydrated: If a person is experiencing diarrhea, it is important to replace fluids. Drinking water and sugar-free electrolyte beverages can help replace these fluids and any lost electrolytes.
• Adding probiotics and prebiotics: Taking a probiotic supplement or increasing the intake of probiotic- and prebiotic-rich foods may effectively support the gut bacteria during a keto diet. Doing this may reduce the GI effects of a keto diet.
• Decreasing the intake of sugar substitutes: Cutting back on the intake of foods and beverages that contain keto-friendly sugar substitutes may help relieve GI symptoms.

Before making any significant lifestyle or dietary changes, it is always worth consulting with a healthcare professional.

Anyone experiencing severe diarrhea or diarrhea lasting longer than a week should consult a healthcare professional.

Similarly, if constipation or other GI symptoms are long lasting or extremely painful, it is best to seek medical attention.

People interested in trying a low carb diet may wish to consider working with a registered dietitian to see what dietary changes would work best for their lifestyle. Less restrictive dietary patterns can often produce similar benefits without the risk of uncomfortable side effects.

A ketogenic (keto) diet is a diet that largely consists of foods that are high in fat and low in carbs. During a keto diet, the body goes into a state of ketosis in which it uses fat instead of carbohydrates for energy.

As the diet can lead to changes in the digestive tract, it may cause adverse GI effects, such as diarrhea.

To relieve diarrhea that is due to the keto diet, people should consider taking steps such as focusing on soluble fiber, taking probiotic supplements, staying hydrated, and easing into the diet.

If the symptoms of GI upset are severe, long lasting, or painful, it is best to seek medical attention.