Does ketosis cause diarrhea? Understanding the Causes and How to Cope

October 16, 2025 •

4 min read

According to one study, up to 40% of people on a ketogenic diet have experienced diarrhea, especially during the initial transition period. If you’ve asked, “Does ketosis cause diarrhea?”, you're not alone, as your digestive system adjusts to a dramatic change in macronutrient intake.

Quick Summary

The ketogenic diet can lead to diarrhea due to a body-wide transition that affects gut flora, digestion of increased dietary fat, and reduced fiber intake. This common side effect is often temporary but can be managed with specific dietary adjustments and careful food choices.

Key Points

High Fat Increases Bile: A sudden increase in dietary fat on the ketogenic diet requires more bile for digestion, and excess bile can act as a natural laxative, causing diarrhea.
Reduced Fiber is a Factor: Drastically cutting carbs often means cutting fiber from sources like fruits and grains, which can disrupt bowel movements and alter the gut microbiome.
Sugar Alcohols are Culprits: Many keto-friendly processed foods use sugar alcohols (like xylitol and sorbitol) that are not easily digested and can cause a laxative effect.
Electrolyte and Water Flush: The initial period of ketosis often results in the body flushing out stored water and electrolytes, contributing to loose stools and dehydration.
Gradual Transition is Best: Easing into the diet and slowly increasing fat and fiber from keto-friendly sources is an effective way to minimize digestive shock and reduce diarrhea.
MCT Oil Can Be a Trigger: Medium-chain triglyceride (MCT) oil, a popular keto supplement, is known to cause gastrointestinal distress and diarrhea if consumed in large amounts.
Gut Adaptation is Temporary: For many, diarrhea is part of the temporary 'keto flu' as the body and gut microbiome adapt to burning fat instead of carbs for energy.

For individuals transitioning to a ketogenic diet, the change in eating patterns can sometimes trigger noticeable side effects. One of the most frequently reported gastrointestinal issues is diarrhea, which can occur for several reasons related to the body's metabolic shift from burning carbohydrates to fat for fuel.

Why Does Ketosis Cause Digestive Upset?

Going from a carb-based diet to a high-fat, very-low-carb diet places new demands on the digestive system. The process of transitioning into a state of ketosis can be an adjustment period, sometimes referred to as the “keto flu,” where digestive symptoms like diarrhea are common.

Increased Bile Production from High Fat Intake

To digest the large amounts of fat typical of a keto diet (often 65–90% of calories), the liver and gallbladder must produce and release more bile. Bile is a natural laxative, and an excessive amount can speed up the digestive process and cause loose, watery stools. For those who consume too much fat for their digestive enzymes to handle, undigested fat can reach the large intestine, leading to a specific type of diarrhea called steatorrhea.

Reduced Fiber Intake and Altered Gut Microbiome

Many high-fiber foods, such as fruits, starchy vegetables, and whole grains, are heavily restricted on the keto diet. A sudden, drastic reduction in fiber can disrupt bowel regularity. Fiber is essential for adding bulk to stool and feeding beneficial gut bacteria. The change in the gut's fuel source causes shifts in the types of bacteria that thrive there, which can trigger digestive distress as the microbiome adapts to a low-carb environment.

Sensitivity to Artificial Sweeteners

To satisfy cravings for sweets, many people on keto turn to products containing artificial sweeteners and sugar alcohols like sorbitol, xylitol, and maltitol. These compounds are not fully absorbed by the body and can have a significant laxative effect, especially in large quantities, causing gas, bloating, and diarrhea.

Electrolyte Imbalance and Water Loss

When the body initially depletes its glycogen (stored glucose) reserves, it releases a large amount of stored water, leading to rapid initial weight loss. This flush of fluids, often called the “keto woosh,” can also speed up transit time in the digestive tract, contributing to loose stools. Without adequate electrolyte replenishment (sodium, potassium, magnesium), dehydration can occur, further complicating digestive function.

Strategies to Manage and Prevent Keto Diarrhea

Increase fiber gradually: Instead of suddenly eliminating high-fiber foods, slowly reduce your carb intake while focusing on keto-friendly, fibrous vegetables like leafy greens, broccoli, asparagus, and avocados. Chia and flax seeds are also excellent sources of fiber.
Introduce fats slowly: Ease into your new high-fat intake rather than drastically increasing it overnight. This gives your gallbladder and digestive enzymes time to adapt.
Limit dairy intake: The high fat content in many dairy products can cause issues, especially for those with lactose sensitivity. Try cutting back on high-fat dairy like heavy cream and cheese to see if symptoms improve.
Choose fats wisely: Not all fats are created equal. Focus on healthy, whole-food fat sources like avocado, olive oil, and fatty fish, which may be easier to digest for some than large quantities of saturated fats from bacon or highly processed oils. Be cautious with MCT oil, as too much can be a potent laxative.
Stay hydrated and replenish electrolytes: Drink plenty of water and consider consuming bone broth or sugar-free electrolyte beverages. This is crucial for replacing fluids and electrolytes lost during the initial stages of ketosis.
Include probiotics: Fermented foods like sauerkraut and kimchi can help restore a healthy balance of gut bacteria. A probiotic supplement may also support your gut microbiome during the transition.

Short-Term vs. Long-Term Causes of Keto Diarrhea


Cause	Typical Onset	Duration	Management Strategy
Increased Bile Production	During the initial transition (keto flu)	Short-term (1–2 weeks)	Ease into high-fat eating; consider digestive enzyme support (with medical supervision).
Reduced Fiber Intake	Initially or throughout the diet	Can become chronic	Incorporate high-fiber, low-carb foods; consider a keto-friendly fiber supplement.
Artificial Sweeteners	Soon after consumption	Persistent with continued use	Eliminate or significantly reduce consumption of products containing sugar alcohols.
Gut Microbiome Shifts	During the initial transition or longer term	Varies, can be ongoing	Introduce fermented foods and probiotics; ensure adequate keto-friendly fiber sources.

What to Do If Diarrhea Persists

For most people, keto-induced diarrhea is a temporary issue that resolves as the body adapts. However, if symptoms are severe, persistent (lasting more than a week), or accompanied by other worrying signs, it is important to seek medical advice. A healthcare provider can help determine if there is an underlying issue, such as a food intolerance or a more serious digestive condition. If a food diary reveals a persistent trigger, that food should be avoided. The most successful diet is one that works with, not against, your body, and chronic digestive discomfort is a strong signal that an adjustment is needed.

Conclusion: Navigating Digestive Changes on Keto

Does ketosis cause diarrhea? Yes, for many individuals, it is a common side effect of transitioning to a high-fat, low-carbohydrate diet. The root causes include the body's necessary adjustments to fat digestion, changes in gut flora due to reduced fiber, and the potential laxative effects of sugar alcohols and excessive water loss. By taking a gradual approach to the diet, carefully selecting nutrient-dense, fiber-rich keto foods, staying hydrated, and addressing specific food triggers, most people can successfully mitigate or eliminate this uncomfortable symptom. However, listening to your body and consulting a professional for persistent problems are key to a healthy and sustainable dietary plan.

Frequently Asked Questions

Yes, keto diarrhea is a common, though not universal, side effect, particularly during the first one to two weeks as your body adjusts to the high-fat, low-carb dietary changes.

For most people, keto-induced diarrhea is temporary and resolves within a few weeks as the digestive system adapts. However, for some, it can persist longer depending on individual tolerance and dietary choices.

To help with diarrhea, incorporate low-carb, high-fiber foods like avocados, leafy greens, broccoli, and chia seeds. Fermented foods like kimchi and sauerkraut can also help restore gut health.

The high fat content in many keto-friendly dairy products can be a trigger for some, especially those with lactose intolerance. Reducing high-fat dairy can help alleviate symptoms.

While anti-diarrheal medication can offer short-term relief, it won't address the underlying cause of keto diarrhea. It is better to focus on dietary changes and hydration to resolve the issue at its root.

You should consult a doctor if your diarrhea is severe, lasts longer than a week, or is accompanied by other symptoms like blood in your stool, severe abdominal pain, or signs of dehydration.

While fiber is usually associated with preventing constipation, a lack of it can also cause digestive issues. Fiber helps regulate stool consistency, and without it, your bowel movements can become irregular and loose.

Yes, consuming too much MCT oil, especially when first starting, is a common cause of diarrhea on the keto diet due to its rapid absorption and potential laxative effect.