Keto Flu Symptoms, Remedies, and Prevention

Medically Reviewed By Adam Bernstein, MD, ScD

Keto flu can be a result of starting the keto diet. Symptoms include headaches, dizziness, cramps, and nausea. When you follow the keto diet, you are removing carbohydrates and eating foods that are higher in fat. This places your body in nutritional ketosis, which is a metabolic state wherein your body is using fatty acids instead of glucose for energy. Ketones build up, and you may feel ill. These keto diet side effects have been dubbed “keto flu.”

There are many options that may help ease your symptoms, including drinking plenty of fluids, taking in electrolytes, and resting. Keep in mind that keto flu remedies are not based on any clinical evidence that they work to relieve symptoms or shorten their duration.

This article explores the symptoms and causes of keto flu. It also covers some strategies to manage the symptoms.

Symptoms of keto flu

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A 2020 study in Frontiers in Nutrition identified common symptoms that people experience when following the keto diet. The researchers used online forums to collect their data, and they selected 101 online forum users who discussed their keto flu symptoms.

The researchers noted 54 distinct symptoms. The most common symptoms include:

  • flu
  • headaches
  • fatigue
  • nausea
  • dizziness
  • brain fog, which may manifest as difficulty with concentration, thought, or memory
  • gastrointestinal discomfort
  • decreased energy
  • feeling faint
  • heartbeat alterations
  • sore throat
  • decreased appetite

When to contact a doctor

If you are considering the keto diet, consider contacting your doctor beforehand. This is especially important to do if you take insulin or other medications for diabetes.

Also, one 2021 article suggests that people do not follow the keto diet for long periods of time. The authors advise a minimum of 2–3 weeks up to 6–12 months Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source .

Contact a healthcare professional if you experience new or unusual symptoms after starting the keto diet. They can perform a physical exam to help determine if a medical condition is causing your symptoms.

Learn more about ketones and the keto diet.

How long does keto flu last?

From the online forum study, users commented that their symptoms peaked in the first 7 days of starting the keto diet and decreased after 4 weeks. This is consistent with a 2018 Healthy Living Newsletter from the United States Department of Veterans Affairs, which indicated that keto flu lasts approximately 1–2 weeks.

Tips to relieve keto flu symptoms

Drinking plenty of fluids and taking in electrolytes — such as salts, potassium, and magnesium — may help Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source reduce cramps and nausea.

Other practical things you can do to ease your symptoms include the following:

  • Make time for rest: Taking an Epsom salt bath may help relax your muscles, and it will also increase your electrolyte absorption. Drinking herbal teas may calm your nervous system and help you sleep.
  • Take part in exercise: Practicing yoga or gentle stretching can help release endorphins, improve your mood, and ease your muscles.

Find out about other Epsom salt remedies.

Can you avoid keto flu?

Strategies that may help prevent or reduce keto flu symptoms include resting and exercising. You can also try the following tips:

  • Slowly reduce your carbohydrates: Slowly removing carbohydrates from your diet may give your body extra time to adjust.
  • Eat more fat: Eating healthy fats is important, as your body will burn fat instead of glucose for fuel. Read about keto-friendly high fat foods.

The keto diet is not safe for everyone to follow. For example, it is not recommended Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source for people who have conditions such as pancreatitis, liver failure, or disorders of fat metabolism. The diet has also been tied to complications such as dehydration and electrolyte imbalances. Also, the keto diet can cause severe hypoglycemia in people who have diabetes and take insulin or medications to help manage glucose metabolism.

Consider talking with your doctor about your overall health before starting the keto diet. Always consult with your doctor before making significant changes to your diet.

The keto diet has only been officially acknowledged as a treatment option for epilepsy in some people.

How the keto diet causes keto flu

While following the keto diet, you are significantly reducing carbohydrates in your diet. This means that your body is no longer storing glucose. Instead, it is burning fatty acids for energy. This is known as nutritional ketosis, or ketosis due to fasting. Being in ketosis builds up ketones, which may be toxic in certain situations. Keto flu is your body’s response to the significant change in metabolism brought on by the keto diet.

There are risks associated with following the keto diet, and the diet is not suitable for everyone. More research to understand the long-term effects of the keto diet is necessary, but some related conditions Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source may include:

Frequently asked questions

Here are some other questions that people have asked about keto flu.

What does keto flu feel like?

Keto flu can feel like the flu. Short-term side effects of the keto diet may include nausea, headaches, tiredness, and dizziness.

Does keto flu mean the diet is working?

There are no well-controlled studies showing that keto flu correlates with keto diet effectiveness. In addition, not everyone who follows the keto diet reports symptoms or side effects, according to the Frontiers in Nutrition study.


Once you start the keto diet and reduce your carbohydrate intake, your body is likely to enter ketosis. You may begin to experience keto flu within a few days. Keto flu may last up to 4 weeks and cause symptoms such as headaches, dizziness, nausea, cramps, tiredness, and difficulty concentrating, among others.

Consult with your physician before starting the keto diet. Also, contact them during the diet if you have any questions or concerns.

Drinking plenty of fluids, increasing electrolytes, resting, getting light exercise, and increasing the number of healthy fats you are eating may help prevent keto flu or reduce symptoms.

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Medical Reviewer: Adam Bernstein, MD, ScD
Last Review Date: 2022 Jun 30
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