What is Keto Flu and How Can You Reduce Its Symptoms?

What is Keto Flu and How Can You Reduce Its Symptoms?

The keto (ketogenic) diet has gained popularity, with many people turning to it for weight loss, managing chronic illnesses, or improving overall fitness. However, transitioning from a conventional diet to a very low-carbohydrate one often presents a challenging hurdle: the keto flu.

Nevertheless, it’s not inevitable if you prepare for it adequately.

Embracing the Keto Flu: Your Journey to Ketosis

The term “keto flu” refers to the transient symptoms that arise following the adoption of a very low-carbohydrate diet, typically involving intakes of less than 50 grams per day. It is also known as the “low-carb flu.”

Although termed flu, it is important to note that the keto flu is not caused by a virus, unlike seasonal flu. However, some of its manifestations are similar to those of the flu.

Keto Flu Symptoms

The symptoms of keto flu are varied and may manifest as:

  • Digestive problems (nausea, bloating, constipation, or diarrhea)
  • Headaches, dizziness, difficulty concentrating, and confusion
  • Bad breath
  • Muscle cramps and pain
  • General weakness, accompanied by fatigue
  • Rashes

It’s important to note that not everyone who embarks on a keto diet necessarily experiences all of these symptoms, and their intensity varies from person to person. Generally, they are most pronounced during the first week and diminish after four weeks.

What Causes Keto Flu?

Keto flu is partially attributed to an electrolyte imbalance that arises when the body enters a state of ketosis. In this state, the primary source of energy shifts from sugar obtained through dietary carbohydrate intake to ketone bodies produced by the liver.

Understanding Electrolytes

Electrolytes are minerals that exist in ionic form, meaning they carry an electrical charge. They comprise cations, which carry one or more positive charges, and anions, which are negatively charged. Examples include sodium (Na+), potassium (K+), calcium (Ca2+), phosphate (PO43-), and magnesium (Mg2+) ions.

Electrolytes play crucial roles in numerous bodily processes, including the transmission of nervous messages, muscle contraction, and the distribution of fluids between cells and the external environment. An imbalance in electrolytes can significantly disrupt bodily functions across multiple levels.

The Keto Diet’s Impact on Electrolytes

Transitioning from a diet rich in carbohydrates to one almost devoid of them results in decreased insulin levels within the body. Insulin, secreted by the pancreas, regulates blood sugar levels downward. Reduced carbohydrate intake leads to diminished insulin production. This phenomenon also accounts for the benefits of this diet for people suffering from diabetes, a condition characterized by poor blood sugar regulation.


Insulin also directly affects the kidneys, instructing them to conserve sodium. Reduced insulin levels promote sodium elimination through urine, resulting in dehydration as water follows suit. Dehydration is a common side effect that appears in the first days of the keto diet.

Lack of sodium can contribute to fatigue, weakness, headaches, and trouble concentrating experienced during keto flu.


In response to reduced sodium levels, the body produces aldosterone in the adrenal glands. This hormone prompts the kidneys to eliminate potassium to maintain sodium balance. Consequently, the keto diet can lead to potassium losses, promoting muscle cramps and potentially heart palpitations.

Keto Diet Causes Temporary Electrolyte Imbalance

These electrolyte-related disorders are transient, as evidenced by a study comparing the effects of two diets, one high in carbohydrates and the other low. The study indicates that sodium losses are more significant in the low-carb diet group for seven days, but this trend reverses after 28 days. Similarly, potassium elimination was higher for 14 days but became identical between the two groups after 28 days.

Switching to Keto May Trigger Digestive Issues

Intestinal disturbances are common when following a keto diet. Diarrhea is the most prevalent digestive issue, often triggered by the high-fat content of the diet. Conversely, some individuals experience constipation due to factors such as dehydration, reduced fiber intake, and decreased food volume.

How to Alleviate Keto Flu Symptoms?

Understanding the root causes of these common problems enables you to explore solutions to manage the symptoms of keto flu and initiate your keto diet under optimal conditions.

1. Combat Electrolyte Loss With Mineral-Rich Drinks

This helps mitigate dehydration, especially during the initial days. However, it’s unnecessary to consume excessive amounts of water, as this could exacerbate the body’s sodium deficit. Determining the precise amount of water to consume daily is challenging, as it depends on various factors. Therefore, it’s best to rely on natural thirst mechanisms and drink regularly, being mindful of any signs of dehydration.

Ideally, prioritize mineral-rich options such as vegetable and/or bone broths. Additionally, moderate consumption of coffee (no more than three cups per day) is acceptable to avoid further electrolyte losses.

2. Increase Your Sodium Intake

To counterbalance the body’s loss of sodium, relying solely on sodium chloride, or table salt, is likely not the most optimal choice. Sodium chloride consists of 40% sodium and 60% chloride ions, which have an acidifying effect on the body.

Instead, using sodium bicarbonate is a more advantageous option. Sodium bicarbonate not only provides sodium but also bicarbonate ions, which possess alkalizing properties. These ions help neutralize the acidifying effect of the ketone bodies produced during the keto diet.

Additionally, certain foods rich in sodium that are permitted on the keto diet can be incorporated. These include seafood, pickles, soy sauce, and others.

3. Increase Your Potassium Intake

To mitigate the inconveniences associated with potassium deficiency, prioritizing foods rich in potassium is advisable. These include:

  • Avocado
  • Brussels sprouts
  • Spinach
  • Certain varieties of asparagus
  • Mushrooms
  • Almonds and hazelnuts
  • Coconut milk

Additionally, you can consider using potassium bicarbonate food supplements.

4. The Medium-Chain Triglyceride Trail

Medium-chain triglycerides (MCTs) are a group of fats easily absorbed by the body, aiding in the transition to ketosis. They are particularly abundant in coconut oil.

A study from New Zealand suggests that 20 days of MCT supplementation, comprising 65% caprylic acid and 35% capric acid, could alleviate symptoms of the keto flu, except for abdominal pain.

5. Adapt Your Exercise for Ketosis Transition

It is advisable to avoid overly intense physical activity at the beginning of the keto diet, a period when performance may be impaired. The body adapts, and performance tends to return to normal after a few weeks.

6. Avoid Calorie Restriction

In pursuit of weight loss and due to concerns about the negative perception of fats, it is common to limit food intake during the keto diet. However, starving oneself can exacerbate the discomfort associated with the keto flu. Moreover, this diet naturally regulates appetite, helping to prevent overconsumption.

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