Keto Flu: Symptoms & Treatment

The ketogenic diet has gained popularity over recent years. Research shows that the keto diet can be an effective treatment for epilepsy.

People also use the keto diet for weight loss, type 2 diabetes, cancer, cognitive and memory enhancement, and neurological and psychiatric disorders.

The keto diet is a high fat, low carb diet. It limits glucose, and this leads to ketone production by the liver. This allows ketone uptake to act as an alternative energy source for the brain.

Many people use the keto diet for weight loss. Evidence shows that minimizing carb intake can cause a few weeks or months of weight loss. It is a proven way to lose weight and improve health. Although the keto diet is safe for most people, it can have some unpleasant side effects. This is what we call the keto flu.

Get Your FREE Eye Health Diet Plan

  • Nine most important vitamins for eye health
  • How to naturally protect and improve your eye health as you age
  • Developed exclusively by our medical doctor

By clicking “Download Now”, I agree to Ben's Natural Health Terms and Conditions and Privacy Policy.

What is keto flu?

Most dietary interventions have some kind of side effects. The ketogenic diet is no exception.

The keto flu is a common result of a keto diet. It involves a cluster of symptoms that often occur within the first few weeks of being on a ketogenic diet. Symptoms seem to peak in the first week and then dwindle after a month or so.

The keto flu is also called the carb flu. This is because the symptoms can be similar to the flu, though this is not a contagious condition. It is hard to describe exactly what happens with a dietary change because only a patient knows their own full experiences.

These symptoms do not only occur with the keto diet. Several patients describe similar symptoms after they cut back on processed foods. Many patients also report these symptoms when following elimination or the anti-inflammatory diet.


The symptoms of keto flu can range from mild to severe. They vary from one person to another. Symptoms include the following:

  • Flu-like symptoms

  • Headache

  • Fatigue

  • Nausea

  • Vomiting

  • Dizziness

  • Brain fog

  • Decreased energy

  • Feeling faint

  • Heartbeat alterations

  • Constipation

  • Diarrhea

  • Irritability

  • Weakness

  • Muscle cramps

  • Poor concentration

  • Stomach pain

  • Muscle soreness

  • Difficulty sleeping

  • Sugar cravings

  • Lack of motivation

Another potential symptom of ketosis flu is frequent urination. When your insulin levels drop, your body responds by releasing more sodium in the urine. This also causes the body to excrete more water. This can lead to higher volume and frequency of urination.

What causes keto flu?

When keto dieters begin eating a keto diet, their bodies are adapting to the fewer carbs. Carbohydrate restriction like this causes your body to burn ketones for energy rather than glucose.

Ketones are byproducts of fat once it’s broken own. In order to enhance the effects of the keto diet, many people also supplement with exogenous ketones. Fats become the main source of fuel when following a ketogenic diet. This process is what we call ketosis.

Normally, fat is a secondary fuel source, only for when glucose is not available. When there are not enough carbs in the diet for energy, the liver produces glucose from fat. This is called gluconeogenesis. Eventually, the liver can no longer produce enough glucose to keep up with the body’s energy demands.

When the body breaks down fatty acids, this produces ketone bodies. Body tissues use ketones as their fuel. This is when the body enters what we call a state of ketosis. Ketosis occurs during starvation and fasting. It also happens during the ketogenic diet. Nutritional ketosis like this is generally safe for most people. However, people can still experience symptoms. Enter the dreaded keto flu.

In general, the recommended carb intake is 200 to 300 grams per day for the average person. On the ketogenic diet, the recommended carb intake is less than 50 grams per day. This is an extreme reduction, and it can be shocking to the body.

People can even experience withdrawal-like symptoms. This is why many of the symptoms you read above are similar to the withdrawal of a substance such as caffeine. It can take your brain and other organs some time to adapt to this new fuel source.

The keto diet is a major change. Your body simply needs time to adapt to this new way of eating. Some people have a harder time adapting to this new way of eating than others.

We don’t know for sure the mechanisms behind the keto flu. However, the following are theories regarding the keto flu:

  • Detox factor

  • Carbohydrate withdrawal

  • Immune reaction

  • Changes in the gut microbiome

  • Losing a lot of water

  • Losing a lot of sodium and other electrolytes

  • Temporary mineral imbalances

Another factor involved in the keto flu is insulin imbalance. A lack of carbs decreases the amount of insulin in the bloodstream. This results in an increase in the amount of sodium, potassium, and water released in the urine. This can cause dehydration.

Insulin is also responsible for transporting glucose to the brain. Before the brain starts using ketone levels as fuel, it will have less energy. This happens at the start of the keto diet, as blood sugar levels adjust.

How to get rid of keto flu

The keto flu will often go away on its own after a few days or a few weeks. This happens after the body adapts to this way of eating. One keto flu remedy is time. You could suffer through those few days or weeks while your body adjusts. Or, you could address the root cause and feel better more quickly.

Do keep in mind that although we call this the keto “flu,” it’s not true flu. You won’t develop a fever or overly severe symptoms. If you feel that your symptoms are severely affecting your life, go to your healthcare provider. This could be something else, and you’ll want to have your doctor rule that out.

Don’t purposely restrict your food intake

If you have the keto flu, you may have nausea or a keto headache. This can reduce your appetite. In this case, it makes sense that your food intake would be lowered. However, if you do have an appetite, it’s important not to restrict your food intake.

Some people on the keto diet get very hungry and worry that they’re eating too many calories. It is not a good idea to focus on caloric intake when you’re trying to adjust to the keto diet. In fact, letting yourself get too hungry or stressing about what you’re eating can make keto flu symptoms worse.

Don’t worry; once you’re in ketosis, your appetite usually decreases. This way, you’ll naturally end up eating less food. It’s always important to pay attention to your body’s hunger and fullness cues.

If you get hungry between meals, have keto-friendly snacks ready to go, like boiled eggs. As much as we don’t want you to get too hungry, we also don’t want you to get too full. You can avoid this by eating slowly and paying attention to your fullness signals.

Stay hydrated

Making sure you drink enough water is good for general health. It can also reduce symptoms of keto flu. This is because a keto diet can cause you to rapidly lose stored water. This can increase your risk of dehydration. This is because of glycogen.

Glycogen is the stored form of carbohydrates. Glycogen binds to water in your body. When you reduce your carb intake, glycogen levels drop, and water is released from the body.

Maintaining proper hydration can help with symptoms such as fatigue and muscle cramping. Replacing lost fluids becomes even more important if you are experiencing diarrhea. This is because diarrhea causes even more fluid loss from the body. The more you weigh, the more water you will probably lose in the early stages of the keto diet. This means you’ll need to replace this with more water.

A good rule is to drink a minimum of 2.5 Litres of fluid every day during your first week of the keto diet. Don’t forget that herbal tea intake contributes to your fluid intake as well. However, do try to keep your caffeine intake to a moderate level. This is because caffeine is a diuretic, and too much of it can lead to dehydration.

Avoid intense exercise

As we all know, exercise is an important health habit. However, if you are experiencing keto flu symptoms, then you should avoid strenuous exercise. When you have the keto flu, you feel tired and have muscle cramps.

Give your body a rest! Avoid activities such as long-distance running, intense weight lifting, and biking. These could worsen your symptoms. However, light activity can actually help to improve symptoms. This includes exercise such as yoga, walking, or leisurely bike rides.

Research shows that physical performance declines during the first week of the keto diet. However, performance recovers and can even improve after four to six weeks. We recommend taking it easy for your first few weeks on the keto diet. Then slowly increase the intensity of your exercise over time.

Replace electrolytes

Replacing dietary electrolytes may help reduce keto flu symptoms. While eating a keto diet, insulin levels decrease. When insulin levels decrease, the kidneys release excess sodium from the body. Ensuring that you get enough of these important nutrients in the diet is a great way to keep the keto flu at bay. You can also use supplements, such as a magnesium supplement, to help with this.

Get enough sleep

Common symptoms of keto flu include fatigue and irritability. If you’re not getting proper sleep, then cortisol levels rise. Cortisol is the stress hormone. High cortisol can negatively impact mood and worsen symptoms of the keto flu. If you are having a hard time sleeping, try the following tips:

  • Reduce your caffeine intake: Caffeine can be overstimulating and impact your sleep. If you consume caffeine, do so at a moderate level and keep it to the morning hours to have less effect on sleep.

  • Cut back on screen time: Try not to look at screens in the two hours before bed. Yes, this includes your TV, computer, tablet, and even your phone!

  • Take a bath before bed: This is a good way to wind down before going to bed. Adding some Epsom salts or lavender essential oil can enhance your relaxing bath experience.

  • Wake up early: Waking up at the same time every day can help with your body’s internal clock rhythm. This can help to improve sleep patterns and sleep quality over time.

Why do some people get keto flu?

People react to the keto diet differently. Some people don’t get the keto flu at all when they start on the ketogenic diet. Others may have symptoms for weeks.

The symptoms people experience are usually connected to how their bodies adjust to a new fuel source. Carbohydrates are the usual source of fuel for the body. When they are reduced, the body uses ketones from fat as fuel instead of glucose.

People who are used to consuming a lot of carbs may have more intense keto flu when starting a ketogenic diet. This is especially true of those who eat a lot of refined carbohydrates, such as pasta, sugary cereal, and pop.

There is no one solid reason why some people adapt to a keto diet better than others. However, we do know that genetics, electrolyte imbalance (magnesium, sodium), dehydration, and carb withdrawal are potential driving forces behind the keto flu.

Who should avoid the keto diet?

The keto diet isn’t necessarily a healthy decision for everyone. For example, pregnant or breastfeeding people may not react to the ketogenic diet in the same way as the average person. These people should only use the ketogenic diet if it’s for therapeutic purposes and under medical supervision. The same goes for children and adolescents.

People with certain health conditions should also avoid the ketogenic diet. This includes people with kidney disease, liver disease, and pancreatic conditions. People with diabetes should consult with their health care provider before starting a keto diet. Their doctor will be able to determine whether this diet is safe or suitable for them and their needs.

There is about 25% of the world’s population that does not react well to dietary cholesterol. For these individuals, the keto diet may not be appropriate.

How long does it usually last?

The keto flu comes on within the first few days of the ketogenic diet. Symptoms usually last about one week. However, it is possible to experience keto flu for longer than this. If an individual has a harder time adapting to the high healthy fat low carb diet, their symptoms could last for several weeks.

As your body adjusts to the conversion of ketones into energy, your symptoms should gradually decrease. As you can see, low carb flu symptoms are common. However, if you’re feeling unwell, then it may be a good idea to contact your health care provider. If you are experiencing diarrhea, fever, or vomiting for a long time, you should contact your doctor. They will be able to rule out other causes of these symptoms.

If you are thinking about transitioning to a ketogenic diet, it’s important that you know what to expect. You may experience some keto flu symptoms. You now know what kinds of symptoms to look out for. Although there is not one specific known cause of the keto flu, you now know the theories behind this condition.


If you experience these symptoms, you now know what to do. Make sure you are eating enough food, particularly fat, carbs, and electrolytes. You can do so by consuming things like bone broth or MCT oil.

Hydrate, hydrate, hydrate. Avoid strenuous exercise, and make sure you are getting enough sleep each night. If all this fails, you may want to slow down your entry into the ketogenic diet.

Perhaps try a “mini-version” of the keto diet first. Ease yourself into it. It can be the quick entry into the keto diet after years of eating a carb-laden diet that is at your detriment.

If you have prolonged symptoms, speak to your health care provider. This way, you can make sure that it really is the keto flu and not some other cause. Otherwise, know that the keto flu only lasts for a few weeks maximum. Once your body has adjusted, you are likely in the clear. 

Top Products

Total Health


Glucose Control