Q&A: What is ‘keto flu’? – Healio

People who start a ketogenic diet may experience influenza-like symptoms in the first few weeks, according to a study published in Frontiers in Nutrition.

Common symptoms of “keto flu” include headache, “brain fog,” and gastrointestinal discomfort shortly after beginning the diet.

To investigate how these symptoms progress, Emmanuelle Bostock, PhD, an adjunct researcher at the University of Tasmania, Australia, and colleagues searched online forums for references to “keto flu,” and gathered individual information on symptom severity and duration.

The researchers found that symptoms peaked during the first week, and typically resolved within 4 weeks of switching to the diet.

To provide physicians with more information on these symptoms, Bostock spoke with Healio Primary Care about the condition, the study results and what to tell patients who want to start a ketogenic diet. – by Erin Michael

Q: What is “keto flu”?

A: Keto flu refers to a cluster of transient symptoms/side-effects associated with the ketogenic diet. The symptoms typically appear within the first few days of dietary adherence to keto. From our research, which analysed 43 online forums, we found that the most common symptoms were “flu,” headache, fatigue, nausea, dizziness, “brain fog,” gastrointestinal discomfort, decreased energy, feeling faint and heartbeat alterations. “Keto flu” is widely reported and discussed in popular media.

Q: Should physicians warn their patients about keto flu if they express interest in starting the diet?

A: Before commencing the ketogenic diet, seeking medical advice is a must. There are a number of medical conditions for which the ketogenic diet is contraindicated, so these must be ruled out. An understanding of the potential side-effects would also assist patients, and these may be monitored by a physician.

Q: Should physicians dissuade certain patients from starting the keto diet due to keto flu?

A: Same as above, and the benefit-to-risk ratio of any medical intervention should be discussed between individuals and their health care providers. It would be important to increase the knowledge of the symptoms, timing and severity of keto flu in physicians. There is very little information in the published literature.

Q: What can be used to treat symptoms of keto flu?

A: We also analysed the recommended remedies of keto flu in the online forums. These were centred upon increasing hydration and correcting electrolyte imbalances.

Q: What additional research is needed on keto flu?

A: The topic of keto flu would benefit from increased knowledge on the pathophysiology of the phenomenon, something which was outside of the scope of the present article.


Bostock ECS, et al. Front Nutr. 2020;doi:10.3389/fnut.2020.0002.

Disclosure: The authors report no relevant financial disclosures.