Keto Diarrhea: What to Do If You Get Diarrhea on a Ketogenic Diet (And How to Prevent It)

Starting a ketogenic diet can bring some noticeable changes—more energy, fewer cravings, and often, steady weight loss. But for some people, the journey can also come with an unexpected side effect: diarrhea.

It’s not the most glamorous topic, but it’s something many people experience, especially in the early stages of keto. And if you've suddenly found yourself spending too much time in the bathroom after starting keto, you're not alone.

The good news? Keto-related diarrhea is usually temporary, fixable, and often preventable. In this guide, we’ll walk through why it happens, what you can do about it, and how to stop it from coming back again. Let’s get into it.

Why Are We Talking About Diarrhea on Keto?

A lot of people jump into the ketogenic diet expecting rapid results. And for many, the diet delivers on that promise. By dramatically reducing carbs and increasing fats, keto shifts your body into a fat-burning state called ketosis. But that shift also forces your digestive system to adapt to a completely different way of processing food, and sometimes, that can lead to digestive discomfort.

Diarrhea is one of the more common side effects, especially during the first few weeks of starting keto. While it’s usually nothing to worry about, it can be frustrating and even exhausting.

This article is designed to help you understand exactly why diarrhea happens on keto, what you can do to stop it, and how to prevent it from returning—all explained in simple terms anyone can understand.

Is It Normal to Get Diarrhea on the Keto Diet?

Yes, it’s surprisingly common—especially in the early stages of keto when your body is adjusting to burning fat instead of carbs.

This shift often comes with a few temporary side effects, sometimes called the “keto flu.” Diarrhea may be part of this. Your digestive system is getting used to a higher fat intake, and that can throw off your gut bacteria, enzyme production, and bile release. All of this can lead to loose stools or more frequent trips to the bathroom.

That said, if your diarrhea lasts more than a few days or feels severe (like watery stools, cramping, or signs of dehydration), it’s worth paying closer attention. While occasional diarrhea is expected, persistent symptoms are not and could mean something else is going on.

Why Does the Ketogenic Diet Cause Diarrhea?

Let’s break it down. There are several common reasons why someone might experience diarrhea on keto, and most of them come down to how quickly your diet has changed.

A Sudden Change in Diet

Switching to keto often means you’re cutting out carbs and replacing them with fats—lots of fats. That’s a big deal for your digestive system.

When you eat more fat than your body is used to, your liver and pancreas need to work overtime to produce enough bile and digestive enzymes to break it all down. If they can’t keep up right away, fat ends up moving through your system too quickly, which can cause loose stools or oily diarrhea.

Also, cutting out carbs usually means you’re also cutting down on fiber-rich foods like fruits, legumes, and whole grains. Without enough fiber, your stool may become too soft or watery.

Too Much MCT Oil or Coconut Oil

If you’re using MCT oil (medium-chain triglycerides) or large amounts of coconut oil as part of your keto plan, this could be the culprit.

These fats are absorbed differently from other fats. MCTs bypass the normal digestion process and go straight to the liver for quick energy. But they also have a well-known side effect—if you take too much at once, they can cause explosive diarrhea.

This is sometimes jokingly called “disaster pants” in the keto world, and it’s very real. Start slow with MCTs and work your way up.

Lack of Fiber

When you ditch carb-heavy foods like bread, pasta, fruit, and beans, you’re also ditching many of the primary sources of dietary fiber. And without fiber, your digestive system struggles to create bulk and form solid stools.

Keto can be done with plenty of fiber, but you have to be intentional about it. Most people simply don’t realize that leafy greens, nuts, seeds, and low-carb vegetables can help fill this gap.

Sugar Alcohols and Artificial Sweeteners

Many keto products are packed with sugar alcohols like erythritol, sorbitol, or xylitol. These low-carb sweeteners taste sweet but don’t spike blood sugar, making them keto-friendly. Unfortunately, they’re also poorly absorbed in the gut and can ferment in the colon, leading to gas, bloating, and diarrhea.

Some people are more sensitive than others, and even small amounts can cause trouble. If you’re using “sugar-free” or “low-carb” desserts, protein bars, or sodas, double-check those labels.

Magnesium Supplements

Magnesium is commonly used on keto to help with muscle cramps and sleep, especially as electrolytes get flushed out early in the diet. But some forms of magnesium—like magnesium citrate or oxide—have a laxative effect.

If you’ve recently added magnesium to your routine, it might be contributing to your symptoms. Consider switching to magnesium glycinate, which is gentler on the stomach.

Hidden Food Sensitivities

Keto diets often rely heavily on eggs, dairy, and high-fat animal products. If you’re sensitive to these foods—especially lactose—then diarrhea might be your body’s way of saying, “This isn’t working for me.”

Even if you weren’t sensitive before, the absence of carbs might make these symptoms more noticeable. It’s also possible that your gut bacteria are reacting to the sudden dietary shift.

Excess Caffeine or Keto Energy Drinks

Caffeine stimulates your bowels, and many people on keto ramp up their coffee or add things like “keto coffee” (with butter or MCT oil) to boost energy. While this can help with mental clarity and fat burning, it can also lead to loose stools—especially if your system isn’t used to it.

How to Fix Keto Diarrhea: Step-by-Step Guide

Now that we’ve looked at the causes, let’s focus on solutions. Most people find relief by making just a few simple adjustments.

Ease Into High-Fat Eating

If you jumped into keto with full-fat everything, try dialing it back a bit. Give your digestive system time to catch up. You can gradually increase your fat intake over a week or two while monitoring how your body responds.

If you’re using MCT oil or coconut oil, start with just ½ teaspoon per day, then work your way up slowly. Some people simply can’t tolerate more than a small amount.

Add More Fiber (The Keto-Friendly Way)

To firm up your stools, you’ll need to bring back some low-carb, high-fiber foods. Good options include:

• Chia seeds and flaxseeds
• Avocados
• Leafy greens like kale and spinach
• Zucchini, broccoli, and cauliflower

You can also try psyllium husk in small amounts to help bulk up your stool—just be sure to drink plenty of water.

Rethink Your Fats

Not all fats are created equal. Some people tolerate monounsaturated fats (like olive oil and avocado) much better than large amounts of butter, ghee, or bacon grease.

Try balancing your fat intake with more whole food sources like nuts, seeds, olives, and fatty fish.

Cut Back on Sugar Alcohols

If you’re using keto treats, protein bars, or sugar-free drinks, check the ingredients list for sugar alcohols. Try cutting them out completely for a few days to see if your symptoms improve. You can reintroduce them slowly to test your tolerance.

Evaluate Your Supplements

If you’re taking magnesium, read the label to see what type it is. Magnesium oxide and citrate are more likely to cause diarrhea, while magnesium glycinate is usually gentler.

Also watch for digestive enzymes or exogenous ketones, which sometimes include ingredients that don’t sit well with everyone.

Track Your Meals and Symptoms

Start a simple food diary and note what you’re eating and when symptoms appear. This can help you identify triggers like dairy, eggs, or certain oils.

You don’t have to give up your favorite keto foods—but finding patterns can make it easier to make smart swaps.

Stay Hydrated and Replenish Electrolytes

Diarrhea can quickly deplete your fluids and electrolytes, especially on keto where you’re already losing water weight. Make sure you’re drinking enough water, and consider adding electrolyte powders or tablets that include sodium, potassium, and magnesium.

When to See a Doctor

Keto diarrhea is usually harmless and temporary, but there are times when it’s best to check with a healthcare provider.

Call your doctor if:

• Your diarrhea lasts longer than 3–5 days
• You see blood or mucus in your stool
• You’re feeling weak, dizzy, or dehydrated
• You’re losing weight rapidly without trying

There could be other causes unrelated to keto, such as a virus, food poisoning, or underlying gut issues. It’s always better to be safe and rule those out.

How to Prevent Keto Diarrhea From Coming Back

Once you’ve resolved the issue, you probably never want to deal with it again. Here’s how to avoid future episodes.

Start your keto journey gradually. Don’t go from zero to 100 on fat intake overnight. Let your digestive system adapt over time.

Support your gut health with fermented foods like sauerkraut, kimchi, or unsweetened yogurt (if you tolerate dairy). These can help build a healthier gut microbiome, which is key for good digestion.

Make sure you’re eating fiber-rich keto foods regularly, and be mindful of how many sugar alcohols and caffeine you’re consuming daily. Small adjustments can go a long way.

Final Thoughts: You’re Not Alone (And It’s Fixable)

If you’re experiencing diarrhea on the keto diet, it’s totally understandable to feel frustrated. But rest assured—it’s a common and usually short-lived problem.

Most people find relief with a few dietary tweaks: cutting back on MCT oil, adding more fiber, avoiding certain sweeteners, or adjusting supplements. And once your body adapts to burning fat, things usually settle down.

The key is to listen to your body, be patient, and don’t be afraid to experiment a bit. Keto can be a powerful tool for health and weight loss, but like any major change, it takes a little time to get right.

And if things don’t improve? There’s no shame in seeking professional guidance to make sure you’re on the right track.

Frequently Asked Questions (FAQs)

1. Is it common to get diarrhea when starting keto?

Yes, it’s quite common. Many people experience digestive changes, including diarrhea, during the first few days or weeks of starting the ketogenic diet. This is usually due to your body adjusting to a high-fat, low-carb eating pattern and changes in gut bacteria.

2. How long does keto diarrhea last?

For most people, keto-related diarrhea is temporary and lasts a few days to a week. If it continues for longer than that, it may be due to specific ingredients (like MCT oil or sugar alcohols), low fiber intake, or food sensitivities. Identifying and adjusting those factors usually helps resolve the issue.

3. What does keto diarrhea look like?

Keto diarrhea often appears as loose, oily, or watery stools. Sometimes the urgency is sudden, especially after eating high-fat meals or using MCT oil. The color may also be lighter due to the fat content. If you notice blood, mucus, or unusually dark stools, see a doctor right away.

4. Can too much fat cause diarrhea on keto?

Absolutely. Eating large amounts of fat—especially suddenly—can overwhelm your digestive system. Your body may not yet be producing enough bile and enzymes to break down all the fat, leading to diarrhea. Gradually increasing fat intake can help your system adjust more comfortably.

5. Does MCT oil cause diarrhea?

Yes, MCT oil is known to cause diarrhea if too much is taken at once. It’s digested quickly and can act like a laxative. If you're new to it, start with just half a teaspoon per day and slowly increase your dose. Some people may not tolerate it well even in small amounts.

6. How can I stop diarrhea on keto fast?

To stop keto diarrhea quickly:

• Cut back on MCT oil or coconut oil
• Add more keto-friendly fiber (like chia seeds, avocados, leafy greens)
• Reduce or eliminate sugar alcohols
• Stay hydrated and replenish electrolytes
• Eat smaller portions of fat and increase intake gradually

If symptoms persist, it’s wise to talk to a doctor.

7. Should I stop keto if I have diarrhea?

Not necessarily. Diarrhea is often a temporary side effect of the transition into ketosis. In most cases, you can continue keto while making adjustments to ease digestion. However, if symptoms are severe or last more than a few days, pause and consult a healthcare provider.

8. What are the best keto foods to eat when you have diarrhea?

When managing diarrhea on keto, focus on easy-to-digest, bland foods like:

• Boiled or scrambled eggs (if tolerated)
• Cooked zucchini or spinach
• Avocados
• Bone broth with electrolytes
• Chia seed pudding
• Soft-cooked salmon or chicken

Avoid heavy oils, raw vegetables, dairy (if sensitive), and sweeteners until symptoms improve.

9. Can I take Imodium or anti-diarrheal medicine while on keto?

Yes, over-the-counter medicines like Imodium can help with diarrhea regardless of your diet. But these should be used sparingly and not as a long-term solution. It's better to identify and fix the root cause of your symptoms instead of just masking them.

10. Can keto cause long-term digestive problems?

For most people, keto doesn’t cause long-term digestive problems if it’s done correctly. However, if you consistently lack fiber, rely heavily on processed keto foods, or have underlying gut issues, problems can persist. A well-formulated ketogenic diet with enough fiber, hydration, and whole foods usually supports good digestion over time.