Does Keto Diet Cause Diarrhea?

Social media makes keto diet fun. Scroll through the hashtag #keto on TikTok and you’ll find plenty of keto recipes: sandwiches made with peppers instead of bread, cucumber dipped in stevia (which looks like watermelon, sugar-free) and “popcorn” ceto made of diced cheese, as well as publications of people who have been successful following the high-fat, low-carbohydrate plan.

And of course, being creative in the kitchen while working to achieve your health goals can be fun! But when certain keto side effects start to appear, this fun often stops. You’ve heard of keto flu and low carb breathing, but there’s another side effect that people feel less comfortable talking about: keto diarrhea.

“It’s so bad I can’t leave the house and I have stomach cramps constantly,” a Redditor said in a Keto Diarrhea thread. “Last night, in the middle of the night, I had to run to the bathroom,” wrote another redditor who was new to the ceto diet. “This has continued all day today and it’s a shame to say the least.”

In the comments, there are other keto devotees who tell the original posters to stick it and that is a normal part of starting keto for some people. But keto diet cause diarrhea? Is keto diarrhea normal? What causes it? Is it forever? And, when should you take it as a signal to stop dieting or consult your doctor?

What is keto diarrhea?

While ketogenic diarrhea is a common side effect, it is not the same for everyone.

Often, keto diarrhea is actually steatorrhea, a specific type of diarrhea caused by too much fat in the stool, says Karie Cassell, RD, dietitian and author of The Domino Diet. Steatorrhea is typically pale, foul-smelling, and may be covered with a thick, greasy film.

It’s also possible that the ketological diarrhea you’re experiencing is just normal diarrhea, characterized by loose, watery stools without excess fat, Cassell says.

Some people experience ketogenic diarrhea during the first few days of starting a diet, while others may start having diarrhea weeks or months later, Cassell says.

What causes keto diarrhea?

High fat content

The main cause of keto diarrhea is the incredibly high fat content of the diet. Fat takes longer to break down in the body than carbohydrates or proteins.

When you suddenly start eating tons of fat, your digestive system may struggle to keep up. Some of the fat may be malabsorbed, not properly decomposed, and therefore not completely absorbed by the body, and excreted in the poop.

This can cause steatorrhea, feces that contain large amounts of fat and look like diarrhea, says Karie Cassell, RD, dietitian and author of The Domino Diet.

Lack of fiber

Another cause of ketogenic diarrhea is a sudden lack of fiber, which leads to such a drastic reduction in carbohydrate intake. “Fiber is used for constipation, so it can be confusing to think of low fiber intake as the culprit for diarrhea,” says Cassell. But insoluble fiber, the type that turns to ice when mixed with liquid, actually increases feces and helps prevent diarrhea, Cassell says.

Artificial sweeteners

Keto desserts can also be a cause of keto diarrhea. “A lot of artificial sweeteners like sugar alcohols are harder to digest,” Cassell says. If you eat a lot of artificially sweetened desserts, you may experience upset stomach followed by diarrhea.

Changes in your gut microbiome

If you have been on a keto diet for several weeks or months and are just beginning to experience diarrhea, it could be due to adverse changes in your gut microbiome. Without fruits, vegetables and other plant foods, you will not get much prebiotic fiber. And without prebiotic fiber, the healthy probiotic bacteria in your gut won’t have the food they need to thrive. Therefore, keto has the potential to worsen your overall digestive health by reducing the healthy bacteria in your microbiome. This can lead to an increase in the frequency of diarrhea and other unpleasant side effects.

Does keto diarrhea last forever?

In most cases, no, keto diarrhea does not last forever. If it’s just a matter of getting your digestive system used to breaking down all this fat, your stools could increase in a week or two. But if your diarrhea is caused by changes in your microbiome, it may continue, says Cassell.

If you experience keto diarrhea for more than a week, Cassell suggests increasing your fiber intake (you can do this by adding starch-free, low-carb vegetables) and eliminating any artificial sweeteners or sugar alcohol.

When should you see a doctor about ketogenic diarrhea?

If your ketogenic diarrhea (or any type of diarrhea) is severe and lasts for more than two days, the Mayo Clinic recommends that you see your doctor. Frequent and continuous diarrhea can cause dehydration, which can be shown as dry mouth, dizziness, excessive thirst, not urinating or dark urine or weakness.

And even if your ketologenic diarrhea isn’t severe but doesn’t go away after the first few days, it may be time to rethink if diet is a good idea for you. No one wants to live life worrying about being a short distance from a toilet at all times.