(Last Updated On: May 10, 2019)

Keto diet has gained enormous popularity in the last couple of years but little is been said about Keto Flu or side effects of Keto.

The other day I came across Alisha (name changed to protect privacy). She was following the keto diet for a month. When she started, her expectation was to lose 5 kgs in a month, instead she ended up feeling terrible.

When I asked her what made her switch to keto, all she had to say is that her friend told her that Keto is the next big thing and that she can lose a lot of weight without restricting calories. What her friend missed out were the finer details that need to be kept in mind when following the keto diet.

Only if Alisha had the knowledge of Keto Flu symptoms and solution to mitigate it, she could have avoided the headache, insomnia and nausea that normally follows after starting keto.

If you came looking for tips on how to avoid keto flu, you will be glad to know that you have come to the right place. You don't have to go through what Alisha had to and that too without getting any result.

If you are already experiencing some of these symptoms, your life will get easy after reading this. If you are still in two minds on taking up the keto challenge, this article will help you to formulate the best approach for starting Keto and avoid Keto flu completely.

Keto Flu Symptoms

Keto flu, in essence, is not the real flu rather a collection of symptoms experienced when first starting the keto diet.

The symptoms are close to that of the flu but I would rather call them withdrawal symptoms from restricting carbs. Yes, you heard it right, carbs are addictive and it can be very difficult to give them up completely.

Apart, from the withdrawal, there is a metabolic adaptation that occurs when switching to any low carb diet. More of this in a bit. Let's first get to know these symptoms.









Stomach Pain

Muscle Cramps

Muscle Soreness

Poor Concentration

Lack of Motivation

Difficulty Sleeping

Bad Breath

When does Keto Flu Kick in and how long does it last?

Keto flu symptoms can kick-in during the first 24 -48 hours of starting with Keto diet.

These symptoms can last from anywhere from 3-5 days to a couple of weeks. Everyone's body is unique and responds differently to the keto diet.

The severity of Keto flu symptoms depends on how metabolically flexible someone is.

Metabolic flexibility is your body's ability to quickly adapt and switch to burning fat instead of glucose.

This flexibility depends on your previous diet (if you were on some form of low carb diet before or not) and your genes.

Some might completely get away without facing any of these symptoms, while others can find it really difficult to adopt the Keto diet.

What is the science behind the Keto flu?

Carbohydrate is the primary source of energy for our body. When carbohydrates are restricted the body has to go through a metabolic change at a cellular level to transition from using glucose for energy to using fats.

This metabolic change is not as easy as a flip of a switch. Over the course of many years living on carbs, our body has almost forgotten to use fat for energy. It is no longer fat adaptable.

This is the main reason for many of the symptoms associated with Keto Flu. The body struggles to maintain blood sugar levels and causes hypoglycemia (low blood sugar). This is accompanied by hormonal changes which result in water and electrolyte imbalance.

Low Blood Sugar

Our body has the capability to generate energy by:

  1. Converting glucose to energy via a process called glycolysis
  2. Converting fat to energy via a process called beta-oxidation

Glycolysis (using glucose for energy) is a more efficient process for the body than directly using fat for energy. The body needs to convert fat to ketones to make it readily available for the brain and other parts of the body. Our brain, in particular, needs a fast energy source.

At the beginning when our body hasn’t learned to produces ketones from fat, an energy deficit is created. This coupled with low blood sugar, make things really difficult for someone switching to fat from carbs.

This is a temporary adaptation phase and the duration is different for everyone. The ease with which you can switch to keto depends on a mix of genetics and your previous diet. If you have followed some form of low carb diet before coming to keto, you will be able to adapt faster.

Water and Electrolyte Imbalance

Electrolytes are the minerals that our body derives from salts, e.g. sodium, potassium, and magnesium. Electrolyte levels in the body are maintained by our kidneys. Electrolyte balance is critical to maintain important bodily functions like heartbeat, nerve signaling, and muscle contraction.

When you stop eating carbohydrates, insulin drops to baseline. Insulin not only maintains blood sugar levels but also signals the kidney to store water. When insulin drops, kidneys no longer get the signal to store water. As a result, water is flushed out along with these important electrolytes.

This is not it. There is another phenomenon that occurs in the liver and muscles.

Our liver and muscles store carbs in the form of glycogen. This is a ready energy source for the body when it is devoid of food (carbs). For every gram of carb that your body stores, it traps three grams of water. Glycogen stores get depleted on the ketogenic diet. This loss of glycogen results in further loss of water and electrolytes in the body.

Stress Response from Hormonal Imbalance

Most individuals when starting with Keto diet, end up eating too few calories as fat in itself is very satiating macronutrient.

Apart from this, they forget to add green vegetables to their nutrition plan. This results in a diet that is both deficient in calories and micronutrients. This puts a lot of stress on the body and raises cortisol (stress hormone). Cortisol released by the body tries to raise blood sugar in an attempt to compensate for the low blood sugar caused by carb restriction. Blood sugar gets completely deregulated.

Carb restriction also results in a decrease in thyroid hormone (T3 in particular). Thyroid hormones are responsible for several functions in the body along with energy (carbohydrate) metabolism. If T3 drops below a certain threshold, it can result in fatigue and lack of focus. Lowered T3 has been hypothesized to improve longevity and preserve muscle mass. It doesn’t appear to cause hypothyroidism in humans with normal thyroid functions.

Things to avoid when you are experiencing Keto flu

When you are sick, it is best not to push your body. Keto flu just like any other sickness limits your body to perform optimally both physically and mentally. It is recommended to avoid the following things until the keto flu symptoms subside.

Physical Activity that is demanding on your body

High-intensity workouts need a readily available source of energy. When you lift weight or sprint, your body taps into glycogen stored in muscles to provide the energy needed to execute the exercise. On a keto diet, the glycogen stores are depleted and it becomes extremely difficult to perform workouts with the same intensity.

After the initial, adaptation phase, you should be able to perform better at the gym if not beat your past records. Yes, that’s right carbs are the go-to source of energy if you want to optimize the process of adding muscles to your frame. But I guess, you are here to lose weight as most people who switch to keto have only weight loss goals in their mind.

You should note though, there will be no loss of performance in endurance type activity like walking, lifting light weights, etc. So don’t stop lifting completely, instead drop a plate or two, until you become keto (fat) adapted.

Lack of sleep

Just like any other type of sickness, keto flu too requires you take more rest. People often feel fatigued when starting with Keto which can increase cortisol levels. If sleep deprivation is added to the mix, it can make Keto Flu worse.

You should try to focus on getting at least 8 hours of sleep.

Try turning off all digital devices with a screen an hour before your bedtime. Blue light from these devices tricks our brain to think it’s daytime and decrease natural melatonin. 

The bedroom needs to be dark and cool when you hit the bed, to create an optimal environment for sleep. If you still struggle to get sleep, you can take melatonin supplements. They are non-habit forming and help you fall asleep easily.

Calorie Counting on Keto

Calories from fat are not the same as calories from carbohydrates. Eating fat vs carbohydrate has a different metabolic and hormonal effect on the body. Fat is slow to digest and doesn’t raise insulin. Whereas, carbs are fast digesting macronutrients that spike insulin.

Over-consumption of food is easy on a high carb diet but difficult on Keto which is high in fat. Fat is very satiating macronutrient.

Still, people try to skim calories as counting calories have been so deeply engraved in us. When starting with any radical diet like keto, counting calories is the worst thing you can do to yourself.

There is no need to track your calories, in the first month on keto. Try to eat enough of healthy fats from whole food sources like Avocados, Eggs, fatty fish, cheese and paneer. This will help you stay satiated without worrying about over eating.

Tip - Avoid processed cheese as they have been engineered for your taste buds. You will easily end up eating more.

Solutions to Common Symptoms of Keto Flu

Keto flu symptoms vary from one person to another. But there are easy fixes for these symptoms.

Headaches and lack of focus

When switching to keto diet, headaches are very common. This mainly occurs due to electrolyte imbalance and dehydration. In the absence of carbs on Keto, insulin is at a baseline and kidneys start flushing out water along with critical electrolytes. These electrolytes are critical to various functions in our body.

Sodium helps maintain the balance of water in and around the cells in our body. It's important for proper muscle and nerve function. It also helps maintain stable blood pressure levels.

Potassium helps in proper functioning of the heart, digestion and muscle function.

Magnesium contributes to muscle and nerve function. It maintains healthy blood glucose levels and plays a part in protein synthesis. It also helps you to relax and sleep.

Recommended intake for Electrolytes:

  • 5000 mg of sodium chloride (salt)
  • 1000 mg of potassium (chloride or sulfate)
  • 300 mg of magnesium (chelated)

Transitioning from a western diet automatically lowers your sodium levels. To add to this, kidney switches to diuretic mode on Keto diet and constantly flushes out water along with other electrolytes.

To combat this, you would need to eat food rich in electrolytes like avocados, salmon, nuts, green vegetables and meat. Chicken and beef broth are great options to replenish electrolytes.

# 1 If you are on the go, try to drink lot of water sprinkled with sea salt all day. It will not only help you to stay hydrated but also maintain focus and energy.
Headaches should disappear once your body has enough electrolytes to regulate various functions.

Stomach Cramps and Constipation

If electrolytes are out of balance in your body, you may be experiencing cramps in stomach. The cramp can also be due to constipation which is very common on keto. Transitioning to any low carb diet will impact gut microbiome and alter bowel movements. If you are not drinking enough water, you can make things even worse.

To balance electrolytes like potassium and magnesium, try to have bone broth and leafy green vegetables daily.

# 2 The fiber from green vegetables will help you to relieve constipation.
There are hardly any pure carbs in leafy greens, so you don’t have to worry about getting kicked out of ketosis.

Distinctive Smell in Breadth

You may experience a breadth that is similar to the smell of nail polish remover when starting out with keto. This is called keto breath. This is nothing but Keto acetone that you are exhaling while breathing.

During the adaptation phase, the body doesn’t know how to fully utilize ketones. The unused Ketones get excreted through urine and while exhaling.

This is not a permanent state and once the body adapts to the Ketogenic diet, it shouldn’t be a problem anymore. In the interim, you can try maintaining good oral hygiene, increase water intake and use a mouth freshener.

Food Cravings, Fatigue and Mood Swings

Most people report low energy levels when starting out with Keto. This can impact physical performance and can last from a few days to weeks depending on how fast the body can create new enzymes for fat metabolism.

The fatigue may be caused by lowered thyroid hormone and an increase in cortisol. Thyroid hormone - T3 in particular decrease as a response to lower carbohydrate intake. Cortisol levels increase as the body struggles to maintain normal blood sugar levels. This can alter your mood and also make it difficult to sleep properly.

While your T3 hormone may not be restored to previous high levels, your cortisol levels usually get restored in a few weeks time. In the meantime, you should focus on increasing your water intake and monitor your electrolyte levels. Try to add a pinch of salt to every glass of water you drink.

#3 If you can have animal broth at least once daily, it will make a huge difference to your energy levels.
#4 Vitamin B5 is an important micronutrient and helps fight fatigue and lethargy. 
#5 It is also important to eat enough food (calories) during this transition phase.

The abrupt removal of carbs and sugar can affect your mood and cause cravings. You can try replacing these foods with low carb alternative or better completely try to give up on all sweet tasting things. It can sound impossible at first but things get easy as time passes.

Who should avoid Ketogenic diet?

Ketogenic diet is an effective tool to accelerate weight loss but it doesn’t mean that it is suitable for everyone.

One of the difficulties with keto diet is to get proper nutrition especially micronutrients - vitamins and minerals. A well formulated Keto diet tries to compensate for most micronutrients but is not ideal for optimal health.

As such pregnant and breastfeeding women should avoid Ketogenic diet.

Children and teenager should not practice Ketogenic form of eating as this is not optimum for their growth. Children with epilepsy are recommended Keto diet under strict medical supervision to control their seizures.

If you are someone suffering from kidney disease, liver disease or pancreatic conditions, avoid keto diet at all cost.

Individuals with diabetes may follow Ketogenic diet but they would need to monitor their insulin and blood glucose levels.

Ketogenic diet is loaded with saturated fats and dietary cholesterol when compared to a regular carb diet. People with sensitivity to dietary cholesterol are recommended to avoid Ketogenic diet.


Keto flu symptoms are very individualistic. Some people find it very difficult to adapt to Keto, while others transition smoothly without any concern. Even for those who experience Keto flu, it is a temporary phase. Things get better with every passing week and your body usually restores to normalcy in 3-4 weeks.

The severity of these symptoms depends on lifestyle factors. If you are coming from a high carb diet, it can be a difficult journey for you. However, if you can get things right from the start, you should be able to manage these symptoms. If there is anything that you want to take away from this article, it should be below.

  1. Drink lot of fluids.
  2. Add a pinch of salt to every glass of water.
  3. Regularly intake bone broth.
  4. Eat enough calories.

If you still can’t figure out where to get started, you can always a book a free phone consultation with us.

Is there anything that I left out? Let me know, in the comments below.


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