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How Long Does Keto Flu Last?

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  Published on August 30th, 2023
  Reading time: 3 minutes
  Last modified July 31st, 2023
Suffering from keto flu

The keto flu is an uncomfortable set of symptoms that most new and experienced keto dieters try to avoid. Who wants to feel tired and groggy with headaches, irritability, and muscle cramps? While many keto dieters seem to skirt this tedious flu, others aren’t so lucky. So, what is the keto flu exactly? How long does the keto flu last? What can you do to avoid it or diminish symptoms if they show up? You don’t have to throw in the keto towel even if you’re dealing with these symptoms because there are ways to tame them and get back to feeling better! We’ll explore the answers to these questions.

 What Is the Keto Flu?

The keto flu is the term for a cluster of symptoms some people might experience when transitioning to a ketogenic diet. You’re more likely to experience these symptoms if you eat a carb-heavy diet and you aren’t metabolically fat-adapted, meaning your body isn’t used to burning dietary fat for energy instead of sugar and carbs

Keto flu might also be called carb withdrawal, because it occurs when glucose (sugar) isn’t available and your sugar intake becomes very low. At this point, you enter the metabolic state called ketosis, your body switches fuel sources from sugar to fat, and your liver begins producing beneficial ketone molecules. [1] As with many things, your body takes time to adjust to this new way of eating and creating energy. 

Carbohydrates also have a proven ability to activate reward centers in your brain. A drastic reduction in carbohydrates and sugar can cause withdrawal-like symptoms. You may be craving the frequent activation of those reward centers in your brain as well as the actual foods.

What Are the Symptoms of Keto Flu?

Keto flu symptoms feel similar to the common flu and can vary from mild to severe. [2]

If you have the keto flu, you might have the following:

  • Fatigue
  • Difficulty sleeping
  • Constipation
  • Skin rash
  • Nausea
  • Headaches
  • Irritability
  • General weakness
  • Muscle cramps
  • Diarrhea
  • Dry mouth
  • Sugar cravings
  • Insomnia

How Long Does Keto Flu Last?

Keto flu symptoms typically last for a few days to a week, but some people might deal with them for a few more weeks. Most people are done with keto flu in less than a week. [3] The thing to keep in mind is that keto flu will not last forever; your body will adjust to this new way of eating.

These unfun symptoms usually show up in the first two or four days of cutting back your carbs, especially if it’s a more drastic shift from your typical diet. The standard Western diet is surprisingly high in processed carbs and sugar, and going keto is a big change. Keto flu tends to be stronger and last longer for first-timers to a very low-carb diet.

Fatigued woman with keto flu

Top Tips to Avoid or Diminish Keto Flu

Most experts believe the primary cause of keto flu is the drop in electrolytes that happens during the transition to ketosis. This is because going keto lowers your insulin levels, which causes your kidneys to increase the excretion of electrolytes. Replenishing your electrolytes as you make the switch can avoid this electrolyte drop and keep those flu-like symptoms at bay. [4]

The fact is that some people are just more metabolically flexible than others. If you aren’t fat-adapted and usually eat a carb-heavy or junk-food-heavy diet, it might be best to slow down your journey into ketosis and gradually drop your carb intake over time. If you drink one or two sugary sodas every day, just leaving those out is a great start for now. 

Check out these other tips to avoid or diminish the keto flu:

  • Stay hydrated
  • Eat a balanced and nutritious ketogenic diet, including mineral-rich natural foods
  • Avoid over-exercising
  • Get plenty of restful sleep
  • Make sure you’re eating enough healthy dietary fat, such as avocado, fish, and olive oil
  • Eat more calories in general
  • Replenish B vitamins 
  • Manage your stress and make time for relaxation
  • Limit or avoid processed foods and unhealthy food additives and preservatives
  • Try intermittent fasting

Did you experience the keto flu? How long did it last? Share your tips and experiences with Ketogenic.com.

Steph Green is a content writer specializing in and passionate about healthcare, wellness, and nutrition. Steph has worked with marketing agencies, written medical books for doctors like ‘Untangling the Web of Dysfunction,’ and her poetry book ‘Words that Might Mean Something.’ In 2016, after four years of struggling with her own health problems and painful autoimmune disease, Steph developed a life-changing and extensive knowledge of keto, nutrition, and natural medicine. She continues on her healing journey and enjoys helping others along the way.



Dhillon, K. K., & Gupta, S. (2023). Biochemistry, ketogenesis. StatPearls Publishing, Biochemistry, Ketogenesis - StatPearls - NCBI Bookshelf (nih.gov)


Bostock, E. C. S., Kirkby, K. C., Taylor, B. V., & Hawrelak, J. A. (2020). Consumer reports of “keto flu” associated with the ketogenic diet. Frontiers in Nutrition, DOI: 10.3389/fnut.2020.00020


Batch, J. T., Lamsal, S. P., Adkins, M., Sultan, S., & Ramirez, M. N. (2020). Advantages and disadvantages of the ketogenic diet: A review article. Cureus, DOI: 10.7759/cureus.9639


Popkin, B. M., D’Anci, K. E., & Rosenberg, I. H. (2010). Water, hydration, and health. Nutrition Reviews, https://doi.org/10.1111/j.1753-4887.2010.00304.x

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