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What Is Keto Flu and How to Reduce Its Symptoms?

What Is Keto Flu

Are you on a mission to lose weight by going on the Keto diet? The low-carb, high-fat ketogenic dietary regimen has really spiked the interest of folks in recent years, due to the diet’s successful results for weight loss, or for maintaining a lean-muscle body. However, many report experiencing unpleasant symptoms, known as keto flu. These are related to the metabolic state the body enters, soon after carbs have been severely reduced. So, what is keto flu exactly?

Keto flu is a term, describing flu-like symptoms you might have in a ketosis state. It is caused by decreasing your carbs intake and eating fatty foods. Fatigue, headache, irritability, constipation, and nausea are some of the side effects you may get during your first week into the keto diet.

Once your body adapts to burning fat for energy instead of carbs, keto flu symptoms will most likely disappear. Keep reading to find out how to alleviate your body’s response to entering ketosis and how to prevent keto flu symptoms.

Key Takeaways

  • At the start of your keto diet, your body needs to adapt to a new metabolic state (ketosis), which promotes the production of ketones.
  • Ketosis can have side effects in the form of flu-like symptoms, known colloquially as keto flu.
  • You can minimize or prevent keto flu symptoms by making sure you don't experience severe sodium deficiency.

How Do You Know if You Have Keto Flu?

Reducing the quantity of total and net carbs you eat when on the keto diet can lead to some people feeling a bit unwell. The reason behind this is that people adjust differently to how their body responds to the new source of energy. As mentioned above, carbs no longer take an active part in the production of fuel (in the form of glucose) for maintaining your energy levels.

To know if you have keto flu for certain, watch out for the following symptoms:

  • Muscle aches and soreness
  • Brain fog and poor concentration
  • Headache
  • Episodes of insomnia
  • Body aches and cramps
  • Nausea
  • Irritability
  • Stomach pains and constipation (or diarrhea)

How Long Keto Flu Symptoms Last

Keto-flu symptoms may last from the first couple of days of decreasing significantly your carbs intake to about a week into the keto diet. Some people, however, may suffer the side effects of being in ketosis for much longer, even for a month. Conversely, others may never experience keto flu symptoms or any general discomfort, as they can easily adapt to any metabolic state and dietary regime.

Related: Whole30 Diet vs Keto Diet - The Key Differences

Does Keto Flu Mean You Are in Ketosis?

Keto flu means that you’re in the process of inducing a new metabolic state, called ketosis. Not everyone experiences keto flu, however, despite entering into a ketosis state when on the keto diet.

What Is Ketosis?

Ketosis occurs when your body no longer relies on carbohydrates for its energy supply. You use up and burn your fat deposits to function instead. The human body naturally produces energy by turning blood sugar into glucose after you ingest carbohydrates with food and drink. Therefore, a low-carb diet, such as the keto diet, hinders this process and induces a metabolic shift to ketosis.

During ketosis, your insulin drops, as glucose levels decrease. Your body starts using up your fat stores. When fat breaks down, your liver increases the production of chemicals, called ketones. Ketones now are the main source of energy for your body.

It’s wise to check your ketone levels, according to Dr. Mark Hyman, who advises that they should be in the range of 0.5 and 1.5 mg/dL, and don’t exceed 3 mg/dL. You can easily do this with ketone test strips, which are widely available.

Note: People suffering from type 1 diabetes are at risk of developing ketoacidosis if they go on the keto diet.

Ketosis Test

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What Causes Keto Flu

A sudden high-carb-to-low-carb diet switch makes your body respond. The reduced level of insulin promotes frequent urination that leads to sodium loss and an electrolyte imbalance. This is the main cause behind your keto-flu symptoms.

Keep keto flu at bay by maintaining a healthy and balanced diet! Take advantage of Cook Unity’s keto meal delivery service in your area and enjoy beautifully prepared and nutritious keto-friendly dishes from award-winning chefs!

Related: Paleo vs. Keto for Inflammation: Which One Works Better?

How to Reduce Keto Flu Symptoms

You can take a range of steps to reduce keto-flu symptoms that may relieve your discomfort, pains and aches. From making sure that you are hydrated to staying on top of your body’s vitamins and minerals requirements, there’s a lot you can do to manage any ketosis side effects.

Check out below how to reduce keto-flu symptoms:

  • Drink more water - Dizziness and headaches tend to go away when your body is sufficiently hydrated.
  • Increase your salt intake - As mentioned above, your body’s sodium levels may drop. So, make sure to add salt to your diet, as sodium has a key role in maintaining a healthy fluid balance in your body.
  • Ensure you get sufficient rest - Get good 7-8 hours of sleep per day, even if this means reducing your caffeine intake.
  • Take additional supplements - Vitamins, as well as minerals like magnesium and potassium, which are electrolytes, can potentially alleviate ketosis-related discomfort.
  • Include healthy fats into your diet - The keto diet is a high-fat dietary program. So, don’t forget to eat a variety of healthy fats if you want to eliminate keto-flu symptoms fast.
  • Eat more fiber - Fiber doesn’t count towards your net carbs intake and suppresses the feeling of hunger for longer. It can also help against constipation.
  • Don’t exert yourself too much - Light exercise is fine but don’t become fanatic with your visits to the gym.

Related: What Fruits Are Keto-Friendly? 8 Healthy Options

How to Prevent Keto Flu

Electrolyte Sources

Image by Drinkhydrant

To prevent keto flu, make sure that you gradually induce and stay in nutritional ketosis. Any sudden changes to your diet are likely to put your body under some stress. So, just take it easy at the beginning and drink enough fluids, such as unsweetened herbal tea and water. Fresh homemade lemonade can also do wonders for any electrolyte imbalance you might experience.

Additionally, you can minimize the risk of getting keto flu symptoms if you focus on eating healthy, whole-food meals. Try not to place your focus on fast weight loss results by restricting your overall food intake or by cutting out carbs completely. On that note, avoid attempting the so-called dirty keto diet that allows processed foods, which are hardly nutritious.

In other words, if you ignore your fiber and microelements intake, and only worry about your macros, the chances are that you’ll quickly deplete your body of important minerals and critical micronutrients. If you become deficient in those, this can induce an electrolyte imbalance and may lead to more severe keto-flu symptoms.

Related: What Alcohol Can You Drink On Keto? Go Keto-Friendly Booze

What Is Keto Flu? FAQs

Q: What Are the Side Effects of Ketosis?

A: The side effects of ketosis can include flu-like symptoms, such as (keto-flu) body aches, headache, gastrointestinal discomfort, nausea, weakness, and more.

Q: How Do I Get Enough Electrolytes on Keto?

A: Sodium, magnesium, potassium, and calcium are electrolytes that you can obtain via supplements and food, such as leafy greens (spinach), vegetables (tomatoes), herbs (dill), fermented foods (kimchi), fish (salmon), mushrooms, fruits (avocado), seeds (pumpkin), nuts (brazil nuts), etc.

Q: Why Do Some People Get Keto Flu?

A: Some people are more sensitive to metabolic changes and may get keto flu. This is especially valid for folks, whose diet, prior to their ketogenic regimen, included predominantly refined carbohydrates.

Q: Does Keto Flu Stop if You Eat Carbs?

A: Yes. Keto-flu symptoms will fade if you increase slightly your carbs intake. You can do this by having more low-carb veggies and fruits if you like.

Q: How Long Is It Safe to Be in Ketosis?

A: According to experts, it’s generally safe to stay in ketosis for up to 6 months. However, a person who is on the keto diet for such an extended period should be monitored to avoid any potential health risks (kidney and cardiovascular damage, for instance).

Related: How Long Does It Take to Lose Weight on Keto?


Keto flu presents itself as a light to moderate discomfort that resembles flu-like symptoms. It’s caused by the shift to a new metabolic state, known as ketosis, during which sodium levels can decrease significantly. To prevent and reduce ketosis side effects, you should stay hydrated, eat whole ketogenic foods that are high in healthy fats, fiber and electrolyte micronutirents. You should also have plenty of rest.