Does the Keto Diet Cause Diarrhea?

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Written by Amanda Johnson, Keto Expert and medically reviewed by Abby Courtenay

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Starting a keto diet is a major lifestyle change. Turning your eating habits upside down can fuel a positive transformation, which we see in the many positive benefits of ketosis, but it can also throw your stomach for a loop.

After all, carbohydrates used to take up about half of your diet (based on how most Americans eat), and now they account for just 5-10%. You’ve cut out many of the foods that your body is used to digesting, and have likely introduced new ones.

It’s not surprising that your stomach may need some time to catch up.

Everyone’s body reacts differently to ketogenic eating. Many people experience constipation, others diarrhea, and some don’t notice any significant changes in their bathroom experience.

So yes, the keto diet can give you the runs.

There are a few different reasons why your body might be reacting this way. We’ll explore the most common ones so you can identify why you’re getting diarrhea on keto and find solutions.


Diarrhea on keto

The first thing to know is that it’s normal to have diarrhea during keto, especially when you are starting a low-carb diet for the first time.

It can vary in severity. You may have loose or watery stools (liquid poops), frequent bowel movements, or both. If watery poop is making you take 3 or more trips to the bathroom a day, congratulations, you officially have diarrhea.

Although this is a relatively common side effect, it should not be ignored. Diarrhea can dehydrate you and prevent your body from getting the nutrients it needs.

Is diarrhea a sign of ketosis?

No, not necessarily. Having liquid bowel movements doesn’t mean that you are in ketosis.

It is possible to have diarrhea and be in ketosis at the same time. But you can also be in ketosis without stomach trouble. Or you can have the runs without being in ketosis.

To find out if you’re in ketosis, you have to measure the amount of ketones in your breath, urine, or blood.

The keto “whoosh” effect

If you’ve done some reading about the keto diet on blogs and social media, perhaps you’ve come across something called the whoosh effect.

As you may have guessed, “whoosh” is not a technical medical term. This so-called phenomenon is not backed up by scientific data.

What is the whoosh effect?

Basically, the theory is that soft and squishy areas of your body can magically become firmer and leaner by suddenly releasing fat and water.

Some people say that watery diarrhea on keto is a positive sign of the “whoosh” effect.

According to them, you wake up one morning and voilá you have “wooshed” your way to weight loss and look visibly thinner.

Again, there is no data to back up this theory. Diarrhea is not something to aspire to, as it can be harmful to your body.

What is really happening?

What you may experience at the start of the keto diet is dramatic weight loss in the form of water loss.

(This may be what the “wooshers” are referring to, because you can see the numbers on the scale drop, but they are wrong about it being related to fat loss.)

You lose water weight because having a low carb intake lowers the amount of glycogen stores. Glycogen retains water, so less glycogen means less water stored in your body1.

So while you may lose weight quickly at first, it’s due to water loss, not fat loss.

This is why you urinate more frequently on keto. It also points to why it’s so important to drink lots of water to stay hydrated, since your body won’t be storing as much water.


Why do you get diarrhea on keto?

There are several different reasons you may be pooping water on a ketogenic diet.

  • You have the keto flu. Diarrhea is a symptom of the low-carb flu that can occur as the body adjusts to new eating habits.
  • Your body isn’t able to process extra fat. Some people have more difficulty processing fat. This can be natural or come as a result of having your gallbladder removed. Your body poops out the fat it doesn’t use, making the stools looser.
  • You’re reacting to sweeteners. Since you cut out sugar, many keto dieters turn to substitutes like sorbitol, erythritol, maltitol, and xylitol, which can cause digestive distress2. Even if you’re not consciously adding these to your recipes, they may be hiding in protein powders or any sugar-free or low-carb products you buy at the store.
  • You’re not eating enough soluble fiber. Many common sources of fiber are high in carbohydrates, so you need to make an effort to get soluble fiber from other sources, like vegetables.
  • You’re having too much caffeine or alcohol. Drinking too much coffee, tea, diet sodas, sugar-free energy drinks, or alcohol can cause a laxative effect3.
  • You’re lactose intolerant. When you cut back on carbs, you might start eating more dairy products. This can expose an intolerance to dairy you may not have been aware of.

Can eating too much protein cause diarrhea?

Indirectly, yes. It’s not the protein itself that would cause a problem, but if you’re eating too much of it, that won’t leave enough room for vegetables and other sources of soluble fiber, probiotics, and prebiotics.

Also, protein powders and bars may contain artificial sweeteners or sugar alcohols that can give you stomach problems.


How long does keto diarrhea last?

The amount of time it takes for keto diarrhea to go away depends on what caused it in the first place. If it’s just a matter of your body adjusting to the new diet, it should go away within a week in most cases, although it may take a few weeks.

The good news is that there are proactive steps you can take to help stop this digestive issue or prevent it from happening in the first place. Keep reading to learn more!

If you are having constant diarrhea on keto for more than 2 days, especially multiple times a day, it’s best to see a doctor to rule out other possible causes and to prevent severe dehydration.


Stop diarrhea on the keto diet

Here are concrete steps you can take to stop diarrhea during a keto diet:

1. Get more soluble fiber.

To treat keto diarrhea, eat more foods with soluble fiber:

  • Avocado
  • Blueberries
  • Broccoli
  • Brussels sprouts
  • Carrots
  • Chia seeds
  • Chickpeas*
  • Eggplant
  • Flaxseeds
  • Kidney beans*
  • Tomatoes
  • Oats*
  • Peas*
  • Psyllium

*Watch your portion size of these foods in order to keep your carb count low.

It is important to get fiber from whole foods, but you can also consider taking a fiber supplement.

2. Reduce your intake of caffeine, alcohol, sugar alcohols, and sweeteners.

Eliminate or cut down on:

  • Alcohol
  • Coffee
  • Diet soda
  • Energy drinks
  • Tea

Check labels of packaged food or drinks, especially those that are marketed as sugar-free or low-carb, for the following ingredients:

  • Sorbitol
  • Sucralose
  • Maltitol
  • Mannitol
  • Xylitol
  • Erythritol
  • Lactitol
  • Isomalt

Any of these can cause stomach issues, especially when consumed in large amounts.

3. Eat small meals and snacks throughout the day instead of a few large meals4.

4. If you suspect you may be lactose intolerant, stop eating dairy and see if your symptoms improve. In addition to loose stools, gas, bloating, pain, and nausea are also signs of lactose intolerance5.

Make sure to drink plenty of fluids when you have diarrhea to help prevent dehydration. In addition to sipping room temperature water, you may want to have some soup or broth to help replenish electrolytes.


How to prevent diarrhea on keto

  • Slowly transition to a low-carb diet. This way your gastrointestinal system has time to adjust to your new eating habits little by little.
  • Eat foods that are high in soluble fiber.
  • Consume low-carb foods with probiotics, like sauerkraut, kimchi, pickles, miso, and yogurt6,  to improve gut health.
  • Reduce or avoid food and drinks with caffeine, alcohol, or sugar substitutes.
  • Stay hydrated.


Other side effects related to diarrhea on keto

Ketogenic dieters may also experience these symptoms, especially when first transitioning to a low-carb lifestyle:

  • Abdominal cramping, discomfort, or pain
  • Bloating
  • Constipation
  • Gas
  • Nausea
  • Vomiting


When to worry

Make an appointment to see a doctor if you have diarrhea for more than 2 days without signs of improvement, or if you also have:

  • Blood or mucus in stools
  • Black stools
  • Severe pain in abdomen or rectum
  • Fever over 102 F (39 C)
  • Signs of dehydration7 (dark-colored urine; little to no urination; dry mouth or skin; severe weakness, dizziness or feeling lightheaded; severe thirst)

Experiencing loose, watery stools 3 or more times a day for 4 weeks or more is known as chronic diarrhea. This could be a sign of a serious underlying condition and should be thoroughly assessed by a doctor8.



Diarrhea is not uncommon on keto, but it should not be ignored. There are proactive steps you can take to prevent or treat stomach issues related to a low-carb diet, such as transitioning into the diet gradually, eating foods high in soluble fiber and probiotics, and avoiding caffeine, alcohol, and sugar substitutes. If symptoms persist or increase in severity, it’s best to see a doctor.



  1. Reedy, Katherine. "The Keto diet: Is eating more fat the key to weight loss?" Arizona State University, College of Health Solutions. Updated 2017-09-06.
  2. "What You Should Know About Sugar Alcohols: An expert weighs in". Cleveland Clinic. April 15, 2021.
  3. "Common Causes of Chronic Diarrhea". International Foundation for Gastrointestinal Disorders.
  4. Flesher, Mary. "Diarrhea and Diet". GI Society: Canadian Society of Intestinal Research.
  5. "Lactose intolerance". John Hopkins Medicine, Health.
  6. "How to get more probiotics". Harvard Health Publishing, Harvard Medical School. August 24, 2020.
  7. "Diarrhea: When to see a doctor". Mayo Clinic. See full article.
  8. Chronic Diarrhea”. NCBI Bookshelf. August 11, 2021.