The Keto Flu: Common Symptoms and How to Remedy Them


Have you tried keto, but didn’t feel so hot? You’re not alone! Read on to learn about the commonly experienced “Keto Flu” phenomenon, why it occurs, for how long, and how to remedy the symptoms. 

What Is Keto?

The ketogenic diet is a diet low in carbohydrates, moderate in protein, and high in healthy fats. 

Consuming this low-carb high-fat diet puts your body into a state of ketosis, where fat is burned as the primary fuel for energy, as opposed to glucose (sugar). 

When fat is burned, ketones are released. 

Ketones are the compounds responsible for providing cellular energy in the absence of glucose.

There is a myriad of benefits to being in a state of ketosis. 

Entering ketosis through a ketogenic diet has been associated with promoting heart and brain health1,2, promoting weight loss3, promoting healthy metabolism, reducing inflammation4, and reducing blood sugar and insulin levels5, to name a few. 

What Is The Keto Flu?

The keto flu is a series of symptoms that some people may experience after starting the ketogenic diet. 

When you switch the primary fuel source for your body from glucose to fat, you force your body to change its “metabolic” machinery (genetic expression, enzyme production, etc.). 

Simply put, forcing your body into ketosis by reducing carbohydrate intake and increasing intake of healthy fats can put temporary stress on your body as it adapts to the new fuel source.

You can think of the keto flu as “carbohydrate withdrawal”. Carbohydrates (linear chains of sugar molecules) and sugar, after all, are quite addictive substances.

Not everyone experiences these symptoms. 

Some people are able to better adapt to a state of ketosis than others. The reasons for this are most likely genetics and environmental factors (i.e., how one’s environment influences genetics).

Keto Flu Symptoms 

The ketogenic diet is a healthy diet, but for some people, transitioning to this new way of eating may be especially difficult. 

As the body adapts to burning fat for fuel as opposed to sugar, some susceptible people may experience several “flu” like symptoms. 

The severity of these symptoms differs from person to person and can range from mild to severe.

The most common symptoms include: 

  • Fatigue
  • Headache
  • Irritability
  • Brain fog & Poor concentration
  • Nausea
  • Dizziness
  • Constipation
  • Muscle cramps
  • Sugar cravings
  • Difficulty sleeping
  • Low energy & Lack of motivation

Other symptoms may include:

  • Vomiting
  • Diarrhea
  • Weakness
  • Stomach pain
  • Muscle soreness
  • Heart palpitations 


The main cause of the Keto Flu is the transition to burning fat as opposed to sugar for most of the body’s energy needs. 

This transition requires the body to change its metabolic machinery. 

Most organs (but primarily the brain), need some time to adapt to this change.

This change is tougher for some people compared to others. 

Typically, the keto transition is hardest for those who are transitioning from eating a diet high in highly-refined carbohydrates and processed foods like pastas, sodas, and cereals.

When you lower your carbohydrate intake and start burning fat for fuel, the production of the hormone insulin begins to drop. This is healthy and one of the main goals of the ketogenic diet (the health benefits of keto arise not only from the production of the healthy energy and signaling molecules, ketones, but also from lowering the chronically elevated insulin levels experience on a high-carb diet, which is responsible for multiple health issues).

When Does Keto Flu Appear?

This differs for every person. However, if you are to experience the keto flu, symptoms typically appear within the first week of the transition. 

Keto Flu symptoms are only experienced during the transition period. Once someone adapts to the diet, the symptoms should disappear. 

However, the length of time that one experiences the symptoms depends on the person, and what you do to remedy the situation.


Despite the many health benefits of a ketogenic diet, the Keto Flu is one of the main reasons why people give up the diet after starting. 

Instead of giving up the diet, consider the following remedies (of course, as always, always consult your healthcare practitioner regarding anything health-related and before starting any dietary protocol, especially if you have underlying health conditions and/or if you are experiencing severe symptoms).

Increase Your Intake of Electrolytes 

One of the effects that the ketogenic diet has on the body is to lower blood insulin levels. 

When insulin levels are lowered, the kidneys begin to increase the excretion of sodium salts from the blood. 

Decreased electrolyte levels are responsible for a number of the keto flu symptoms mentioned above.

In addition to this, most people do not consume enough potassium when switching to a keto diet, since the diet contains low levels of fruits and starchy vegetables. 

An excellent way to increase potassium intake is to consume leafy greens, cruciferous vegetables, and avocados (an excellent source of healthy fats in addition to being high in potassium).

Another important electrolyte that can remedy keto flu symptoms is magnesium.

Magnesium is a wonder element. Aside from playing an important role in neurotransmitter regulation, cardiovascular and muscle health, and gene maintenance6, it also can help to remedy some keto flu symptoms such as cramping and nausea, and sleep issues.

It is estimated that only 52% of people in the US are consuming the recommended daily amount of magnesium.7

Drink Plenty of Water and Stay Hydrated

The ketogenic diet by nature is diuretic. As mentioned above, a side effect of the keto diet is that your body begins to excrete salts. When this occurs, fluid also leaves the body. 

Additionally, glycogen levels drop on the ketogenic diet. Glycogen is the stored form of carbohydrate in the body. In the body, water binds tightly to glycogen. When glycogen levels drop, water is excreted.8

Get Plenty of Sleep

In addition to disrupting brain health, lack of sleep can cause cortisol levels to rise, which can cause a host of issues, including keto flu symptoms. Cortisol can also exacerbate keto flu symptoms, making them more severe.

If you are having difficulty sleeping, try any of the following tips:

  • Stop working at least one hour before going to bed: e.g. stop checking emails and working online etc.
  • Avoid physical exercise or strenuous activity at least two hours before bed.
  • Eat your last meal at most four hours before going to sleep (no later).
  • Reduce exposure to blue light before bed. Blue light has been shown to disrupt our circadian clock. You can do this with eye masks, and/or by placing blue light shields on your smartphones or electronic devices.
  • Eliminate all other light illuminations, e.g. from lamps. Even though they’re not a significant source of blue light, these light sources still can stimulate the brain.
  • Consider taking a high-quality melatonin supplement. Melatonin is a hormone made by the body that regulates circadian rhythms. It also is a powerful antioxidant. 
  • Prepare your day in such a way that the most stressful activities, or those which demand the most energy, are reserved for the earliest part of your day (the farthest from bedtime).
  • Take magnesium before bed.

Avoid Strenuous and Intense Exercise

While your body is going through the keto transition, it is important to not cause extra stress on your body. Your body is already experiencing a form of stress by switching its metabolic machinery to adapt to ketosis. Don’t exacerbate this by performing high intensity or strenuous exercises while starting the diet.

Save the high-intensity workouts for when you officially adapt to ketosis. This will help ensure a smooth and fast transition into ketosis, and will help you avoid symptoms of the keto flu.

Tools & Keto Products

Here is our list of recommended products and tools to help you achieve success on your keto journey:

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