The ketogenic diet or popularly known as the keto diet is a very low carb, moderate protein, and high-fat diet. It allows the body, or rather the liver, to produce small fuel molecules called “Ketones”, an alternative fuel source when blood sugar (glucose) is in short supply. Furthermore, when the body produces ketones, it enters a metabolic state called “Ketosis.” At this point, one may experience headaches, fatigue, difficulty focusing (brain fog), cramps and even changes in bowels (diarrhea and/or constipation). This is called Keto Flu.

What is Keto Flu and Why Does it Happens?

People may feel one or more of these symptoms during the first week of the Keto diet. This is not really the flu or even contagious. This is just a term used to describe flu-like symptoms associated as the body started switching from burning glucose to burning fats for fuel. Moreover, this is the symptom of “withdrawal” from carbohydrates.

As the body doesn’t have enough carbs to use for energy, the liver begins to produce glucose for energy using its stores. This process is called “Glucogenesis”. Sooner or later, the liver wouldn’t be able to produce enough glucose. The body will start to break down fatty acids, which will produce ketone bodies, in a process called “Ketogenesis”. Ketone bodies are then used as fuel, and the body enters a state of ketosis.

The amount of insulin decreases in the bloodstream, thus, people may experience an increase in the amount of sodium, potassium, and water that is released in the urine.

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Keto flu varies from one person to another. It may be shorter to one person that may last for only a few days, while the other may experience for up to several weeks. It may be worst for someone and on the other hand, symptoms may be mild to another one.

Here are some common symptoms:

    1. Headache
    2. Fatigue
    3. Dizziness
    4. Nausea
    5. Vomiting
    6. Insomnia
    7. Constipation
    8. Lack of motivation
    9. Temporary hair loss
    10. Poor focus and concentration

Here are other symptoms that usually occur between day 1 and 4 of the diet:

    1. Muscle cramps
    2. Palpitations
    3. Bad breath
    4. Diarrhea
    5. Rash
    6. General weakness

And here are short term symptoms that are preventable and easy to treat:

    1. Dehydration
    2. Low energy
    3.  Hypoglycemia


  1. More water and sodium being flushed out of the body. One of the functions of insulin is to trigger the kidney to hold sodium and water. As soon as insulin levels drop, sodium is released from the body taking water along, thus causes up to 10 pounds of water weight to be lost during the first 5 days of ketogenic diet. Glycogen loss and low insulin levels cause to excrete so much water and sodium that we experience some of the most common keto flu symptoms. These are  dizziness, nausea, cramping, headaches, and gastrointestinal issues. Fortunately, these symptoms can be avoided by drinking plenty of water and supplementing with the right minerals. 
  1. Another cause is the decrease of T3 Thyroid Hormone levels complete carbohydrate restriction leads to up to 47% decrease in T3. T3 is the most potent thyroid hormone that our body makes. 

In a study done with 8 groups of obese individuals, researchers found that different amounts of dietary carbohydrates affect T3 and reverse T3 levels in different ways. T3 levels only decreased when the subjects consumed 120 grams of carbohydrates per day or less (regardless of how calorie-restricted they were). Reverse T3 levels, on the other hand, began to increase when carbohydrate intake was between 40 and 50 grams of carbohydrates per day. This reflects that restricting carbohydrates to that level is impacting thyroid function and causing some keto flu symptoms.

  1. The third cause is the increase in cortisol levels. You will know if you have higher cortisol levels than before if you feel generally irritable and your sleep quality decreases. However, when you addapt to keto diet, your cortisol levels will decrease. you will be using more ketones and fat for fuel instead of sugar which will take a few weeks from the start of the diet. 
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     People experiencing symptoms of Keto Flu are due to these changes. Fortunately, this is just temporary. Symptoms may reduce once the body reached the state of nutritional ketosis. There are even some remedies that can relieve most or all of these symptoms and feel the benefits of your new eating lifestyle.


  1. Top on the list is to increase water and electrolyte intake. Loss of salt and water/electrolytes is responsible for most keto flu.  There are electrolyte supplements available over the counter. You may opt to increase your salt and water intake. A consumption of at least 1 teaspoon of sea salt is recommended. For a tastier alternative, consume bone broth, bouillon, chicken or pork or beef stock. Add a pinch or two on these broth. You can also make a concoction of just sea salt or Himalayan pink salt and water, lemonade adding some sea salt or ACV (apple cider vinegar) water with pinch of salt. Moreover, coffee and tea contribute to your fluid consumption.

In addition, incorporate electrolyte-rich foods such as avocado, nuts, fish, dark green leafy vegetables and fermented vegetables.

Increasing water and electrolyte intake will help alleviate most of the keto flu symptoms such as headaches, dizziness, lethargy, cramps, palpitations, and others within 15 to 30 minutes. This may also help another issue that some people experience: constipation.


  1. Increase in healthy fat intake. Increasing fluid and salt intake usually resolve most of the keto flu but the increase of fat intake will help out more especially if you are still feeling poorly. A well-balanced keto diet includes enough fat so that you are not hungry after a meal. can go for several hours without eating, and have ample energy. 

Supplementing with MCT oil can also help tremendously.

  1. Exercise moderately

    . Activities like intense biking, running, weight lifting and strenuous workouts should be avoided for a while when your body is still adapting to the new fuel source and it is a good idea to give your body a rest. Walking, stretching, or doing gentle yoga or other mind-body exercises should be fine and may even help you feel better.

  1. Do not restrict food consciously. Focusing on calories or macronutrients when you’re trying to become keto-adapted is not a good idea. Letting yourself get hungry or stressing about the amount of food you’re eating may actually make keto flu symptoms worse. Once you’re steadily in ketosis, your appetite will likely go down, and you’ll naturally end up eating less.

Eat as much of the allowed foods as needed until you are no longer hungry and have carb-free snacks.It helps hard-boiled eggs available in case hunger strikes between meals.

While keto-flu symptoms are commonly reported by those shifting to a ketogenic diet. if you are feeling particularly unwell and experiencing symptoms like prolonged diarrhea, fever or vomiting, it’s best to contact your doctor to rule out other causes.

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Is being in Ketosis safe?

When the body produces ketones, we can say we have  ketosis. Ketosis is considered safe unless a person is:

  • Taking diabetes medication
  • Taking hypertension medication
  • Breastfeeding
  • Pregnant
  • A child
  • A Teenager
  • Having any kidney disease
  • Suffering any liver disease
  • Having any pancreatic condition

Is Keto Flu a Sign of Ketoacidosis?

Keto flu is not the same as ketoacidosis. People on the keto diet do not have ketoacidosis. Although they both involve the production of ketones in the body, ketosis is generally safe while ketoacidosis can be life-threatening.

Ketoacidosis is a metabolic state that cause uncontrolled production of ketone bodies that cause metabolic acidosis. It is also a condition that results in changes in blood pH and requires medical attention. The most common cause of ketoacidosis is Diabetic Ketoacidosis. But  alcohol do such things, medication, toxins and rarely starvation.


Most people  experiencing keto flu reported experiencing general fatigue, headaches, and abdominal symptoms. Research shows that the Ketogenic diet is safe and the symptoms are minor and will subside as time goes by and easily manageable. Making certain dietary changes – including consuming plenty of fluids and electrolytes – can help manage symptoms of the keto flu.  Research enough on many different diets to encourage diversity and break monotony to keep things interesting

Attribution: Photos created by freepik.


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