what is keto flu

What is Keto Flu & Should You Worry About It?

You may find yourself with flu symptoms after you started the keto diet. These symptoms do not mean the Keto diet is not for you, or that the diet affects you negatively. You may simply be experiencing what many call “keto flu”.

What is Keto Flu?

The Keto Flu is a group of flu like symptoms that may start appearing a couple of days to a week after beginning with the Ketogenic Diet.

The symptoms may look like this:

  • Nausea
  • Diarrhea
  • Stomach pain
  • Constipation
  • Vomiting
  • Dizziness
  • Muscle cramps
  • Poor consentration
  • Weakness
  • Irritability
  • Fatigue

What causes Keto Flu

 When you reduce your daily carb intake you force your body to burn ketones for energy instead of the usual glucose.  The body normally converts carbs into glucose.

Ketones are the chemicals that your liver produces when your body does not have enough insulin to turn into glucose, sugar. Your body then needs another source to fuel itself, so it uses ketones.

Your liver will turn your fat into ketones, which is sent to your bloodstream. Your muscles and other tissue can then use the ketones as fuel to function properly. Your cells also start to rely on ketones to produce energy and function.

The Ketosis process usually happens under very specific circumstances, like fasting. Ketosis can also happen under the influence of a low carb diet.

The sudden reduced amount of carbs can send your body into shock. This is what causes the flu symptoms. Okay, this sounds a bit drastic – but don’t worry. It’s usually not as bad as it sounds, and the symptoms should subside soon.

How long does keto flu last?

The Keto Flu symptoms will likely begin a day or two after reducing carbs. It can take a few days to manifest, however. For most people the keto flu will last about a week more or less. In very extreme cases the keto fly will last a month. For keto flu to last this long is very rare, fortunately.

Some people never experience the symptoms of the keto flu. This doesn’t mean that you cheated or didn’t do it the right way. It can mean that your metabolism can shift more easily than other people who started the keto diet.

How to reduce the effects of Keto Flu

The Keto Flu makes a person feel horrible. If you have the effects of the keto flu, however horrible it may be, don’t give up. That means your body is going trough change and that you are one step into the right direction.

 There are a few things you can do to relieve the effects of the keto flu.

Keep yourself hydrated

Glycogen, a form of carbs that binds to the water, is stored in your body. When carbs in your body is reduced, the glycogen levels will fall. Water helps to work the glycogen out of your body.

Being and staying hydrated can help with the keto flu symptom like muscle cramping. It is also very important to stay hydrated if you experience diarrhea symptoms. Diarrhea is known to contribute to dehydration.

Get enough sleep

Fatigue is one of the symptoms that a lot of people experience when beginning the keto diet. When you don’t get enough sleep, on the keto diet or not, it will make your cortisol levels rise. Cortisol is the hormone your body produces when you feel stressed.

The lack of sleep and the rise in your cortisol levels can make your flu symptoms worse.

Avoid harsh exercises

Doing daily exercises will help a lot in your overall keto diet journey. At the same time, know your limits. Too much exercise means pushing your body too far. Some of the keto diet symptoms will include muscle cramps and poor concentration.

 Strenuous exercises like hiking, swimming or boxing must be put on hold for the duration of the keto flu period.  Exercises like these may be dangerous to attempt while your body is getting used to new fuel resources.

Why don’t everyone get Keto Flu

The Ketogenic diet is often described as a lifestyle and not a diet. Like with most lifestyles people adapt to it differently. The symptoms people experience depends on what they consumed on a daily basis before starting the keto diet.

People who limited their carb intake or just didn’t eat much carbs before the keto diet will have light symptoms. Many of these people won’t experience any symptoms at all. On the other hand, if you lived unhealthy with a lot of sugary and carb loaded products in you daily eating routine, you may experience the keto flu more than others when your carb intake suddenly drops.

Some people also ensure they start the keto diet with a proper plan. This may include learning what not to eat on the keto diet, as well as having a meal plan that provides a full overview of the next week or month’s meals.


The Keto flu is a manifestation of flu-like symptoms that happens when your body starts burning ketones instead of carbohydrates for its energy resource. Stay hydrated, get enough sleep and be patient. The symptoms usually subside in about a week – and at that point, you’ll be one step closer to your goals.

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