The “keto flu” can be unnerving if you don’t understand it.

Without prior knowledge, the symptoms can lead a new keto dieter to believe the diet isn’t working for them. Thankfully, that’s not the case at all!

The keto flu is a natural reaction to entering ketosis, it’s very temporary, and there are ways to remedy it. We’ve included all the details you need to know about the keto flu and what to do if you experience it.

In this article, you’ll learn:

What is the Keto Flu?

Your body burns carbohydrates (glucose) for energy by default.

But when your carb intake is drastically reduced, like on the ketogenic diet, your body is depleted of stored glucose and instead turns to burning fatty acids for energy. This is the metabolic process of ketosis.

The keto flu is a natural reaction to our bodies are entering ketosis and switching to a state of glucose-burning to fat-burning.

Your body’s response to entering ketosis can often mimic symptoms of the flu, thus the name “keto flu.”  

The Common Symptoms of The Keto Flu

Most people experience the keto flu when they first start keto. Here are some of the most frequently reported manifestations of it:

  • Stomach aches or pains
  • Brain fog
  • Dizziness or confusion
  • Nausea
  • Irritability
  • Diarrhea or constipation
  • Muscle cramping or soreness
  • Lack of concentration or focus
  • Trouble falling or staying asleep
  • Sugar cravings
  • Heart palpitations

Keto flu symptoms usually occur within the first day or two of starting a ketogenic diet, and the severity and length of symptoms vary per person. Some people may have no symptoms at all, while others could experience several for up to a week or two.

Either way, the symptoms shouldn’t last more than a couple weeks and should go away once your body is adapted to burning fat for fuel.

What Causes the Keto Flu?

The keto flu is essentially the result of three things:  

  1. Becoming fat-adapted or keto-adapted.
  2. Electrolyte loss and dehydration.
  3. Withdrawal from carbohydrates and sugary foods.
  4. Lack of Micronutrients

#1: Keto-Adaptation

Our bodies have two primary sources of energy:

  • Glycolysis: converting glucose into energy
  • Beta-oxidation: converting fat into energy

Keto-adaptation means getting the body used to the process of beta-oxidation. This is easier for some bodies than others.

Metabolic flexibility refers to how well a person can adapt to using a different fuel source: switching from burning glucose to burning fats.

Those with less metabolic flexibility are more likely to experience keto flu symptoms as their body adjusts to using fat for energy.

Genetics also play a part. Some people are simply better able to handle the energy switch.

#2: Electrolyte Imbalance

When you make the radical switch of cutting out the high-carb processed foods you find in The Standard American Diet (SAD), your body will rapidly lose water.

This is because all the glycogen (stored glucose) you’ve been accumulating on a high carb diet is bound to water in your body (each gram of glycogen is stored with 2–3 g of water).

When you go keto, your cells use up all that glycogen, and the water holding it has to be flushed out. 

All this water flushing out of your body will carry electrolytes with it, which causes dehydration and electrolyte imbalances.

This can cause flu-like symptoms until everything becomes balanced again.

#3: Carbohydrate Withdrawal

Some research has shown sugar affects the brain in a way similar to heroin or cocaine[*]. It’s pleasurable, and we get a nice shot of the “feel good” hormone, dopamine, when eating sugar.

Plus, the addictive nature of these foods doesn’t help[*].

When sugar is drastically reduced from starting a keto diet, we can experience withdrawal effects like mood swings, irritability, cravings for sugar, and other symptoms of the keto flu.

Someone who has come from eating a diet full of processed and refined carbs and sugars is more likely to also experience these withdrawal-like symptoms and have more trouble adapting to fat burning.

Now that we’ve covered the main reasons behind the keto flu, let’s talk about how to alleviate these issues.

#4: Lack of Micronutrients

One of the easiest traps ketogenic dieters can fall into is not getting enough micronutrients from their diet. 

When you cut out vegetables, fruits, and grains, you need to eat adequate amounts of keto-friendly foods to get the micronutrients you were getting from those foods.

For example, if you stop eating carbs and start eating primarily eggs and cheese to stay keto, you’re at risk of creating nutrient deficiencies.

You need to eat a wide variety of nutrient-rich keto foods (such as organ meats) to make sure you stay healthy in your keto transition.

It’s also important to avoid foods on your keto diet that will make you unhealthy.

Supplementing with micronutrients can also help.

How to Get Rid of the Keto Flu: 5 Steps

Although the keto flu is temporary, there are things you can do to reduce or even eliminate symptoms during the transition into ketosis.

If you suspect you’ve been hit with the keto flu already and it’s too late to prevent it, here’s what you can do to get rid of it:

#1: Stay Hydrated

The water loss that occurs at the beginning of a ketogenic diet needs to be replenished.

Make sure you’re drinking plenty of water throughout the day to help reduce symptoms like headaches, fatigue, or nausea that are often caused by dehydration.

Here’s how:

  • Keep water near you to drink regularly throughout the day.
  • Always drink when you feel thirsty.
  • Often thirst is a sign of dehydration already, so try to get ahead of it.
Takeaway: Drink more water to get rid of headaches and fatigue.

#2: Replenish Electrolytes

As mentioned above, electrolyte imbalances can cause keto flu symptoms. Here are some of the best ways to mitigate this:

    • Increase your salt intake. This will help counteract the water loss that happens when starting a keto diet and replenish sodium.Get your sodium from Himalayan Pink Sea Salt instead of regular table salt. 
    • Supplement with magnesium.
    • Eat keto foods high in potassium like leafy green veggies, salmon, nuts, avocados, or mushrooms.
    • Eat keto foods high in calcium like leafy greens, sardines and salmon.
    • Drink bone broth. Bone broth is not only incredible for your skin, but it provides electrolytes like sodium and potassium while also being hydrating.
    • Take an electrolyte supplement. If you need instant relief, taking an electrolyte supplement will help replenish yours faster than foods can. See our Vitamin and Mineral Supplement guide for more.
Takeaway: Take an electrolyte supplement to balance your electrolytes.

#3: Exercise

Exercise performance may temporarily suffer while your body is adapting to higher fat and low carb intake.

At the same time, getting light exercise 2-3 times per week can help make your body more efficient at switching between carbs and fats for energy (also known as metabolic flexibility)[*], which helps to decrease keto flu symptoms more quickly.

Takeaway: Exercising can boost metabolic flexibility and get you off the keto flu quicker.

#4: Increase Fats 

Your body is no longer getting its energy from carbohydrates and sugars, so it needs plenty of fat for fuel. Make sure the calories from carbs are replaced by eating plenty of keto-friendly fats.

Supplement with MCT oil powder to help further increase ketone levels for fuel.

If the keto flu is persisting longer than a week, re-evaluate your macros. You might still be eating too many carbs and not enough healthy fats.

Sometimes, people think they’re transitioning into ketosis when in reality hidden carbs can be holding them back.

Takeaway: Make sure you’re reducing carbs enough and eating more keto-friendly foods to transition to ketosis.

#5: Take Exogenous Ketones

Remember that one of the reasons you may have the keto flu is your body is trying to become keto-adapted — which means creating and using ketones for energy.

Exogenous ketones are ketone salts you can ingest.

They provide your body with additional ketones to help it become more fat-adapted and enter ketosis more quickly. This can be really helpful in preventing or even eliminating keto flu symptoms.

Takeaway: Supplement with exogenous ketones to become keto-adapted quicker.

How To Prevent The Keto Flu: 3 Steps

If you’re just starting the keto diet and want to prevent the keto flu altogether, it can be easily avoided if you follow these steps:

#1: Follow A Nutritious Ketogenic Diet

One of the main reasons beginner keto-ers start to feel unwell on keto is a lack of proper micronutrients in their diet.

The ketogenic diet is not just about macronutrients. You could technically hit your macros by eating nothing but cottage cheese, but that would lead to nutrient deficiencies and, eventually, the keto flu.

The key to transitioning to keto with few to no side effects is starting with a healthy ketogenic diet that covers all your nutritional needs.

Here’s a list of all the healthy foods you can eat on a ketogenic diet 

You can follow this 7-day meal plan to get used to eating keto. 

It’s also important you avoid unhealthy foods that raise your blood sugar, insulin levels, and kick you out of ketosis.

Takeaway: The key to winning at keto is following a healthy ketogenic diet that covers all your nutritional needs.

#2: Get Plenty of Sleep

Getting at least seven hours of sleep a night is important for anyone, and even more so for the keto dieter.

Your metabolism is getting used to switching fuel sources, so getting plenty of sleep can help reduce stress and fatigue.

If you struggle to get enough sleep per night, try incorporating a power nap or two into your day.

Takeaway: Getting plenty of rest while your body adjusts to using fat for fuel can make the process easier on your body.

#3: Take Adequate Supplements

The easiest way to avoid side effects when you first start keto is to take the right supplements from the start.

Your keto diet should be based on healthy whole foods, but supplements can help fill in any nutritional gaps and make your life easier.

Here are the supplements you should take for different goals:

Takeaway: Taking the right supplements from the start can help you avoid keto flu symptoms altogether.

Takeaway: How To Get Rid Of The Keto Flu Now

The ketogenic diet is a great tool for improving your health,weight loss and feeling your best, but the keto flu can get in your way if you don’t know how to get over it.

If you already fell victim to this common hurdle, do this right now:

  • Drink more water
  • Take electrolytes
  • Drink bone broth
  • Increase your intake of high-quality fats
  • Do light exercise if you can
  • Take exogenous ketones to enter ketosis

If you haven’t gotten the keto flu and want to avoid it all together, prioritize this:

Be Patient and Take Care of Yourself

Use the healthy tips above to help reduce symptoms and possibly even avoid the keto flu all together. Also keep in mind that the keto flu induction phase is just the beginning, and if you experience it, symptoms will subside — just give them time.

Once the hard part is over, you’ll be reaping the benefits of keto and thanking yourself for staying strong.


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Responses (15)

  1. This was very helpful. I’m experiencing at least half of these symptoms and am really struggling so will incorporate some of your suggested helps.

  2. I’ve been on the keto diet for about 45 days, ad no issues at first but now I am experiencing many of these symptoms. Any ideas on why this is happening?

  3. Been on it for almost a month. I have sour stomach, weakness, sleeping is off, dizziness, light headedness and just feel like crap. Need to exercise but don’t have energy.

  4. I’m only two weeks into it I get to sleep just fine it’s staying asleep what’s hard. I woke up today with no energy and feeling like I had to vomit. I went back to sleep till 3 pm. I hope this goes away fast cause I have work and a family to take care of. I don’t want to cut my self short and cut my self off this diet cause it is working.

  5. Two weeks in and yesterday felt hot and sweaty with tummy pains…..now diarrhea. Urine test strip was dark purple so lots of ketones in my wee. Feeling hot and sweaty.
    Strangely though feel like my fibromyalgia brain fog has completly lifted and have more energy. Doing intermittent fasting and having two meals in an eight hour window.
    Going to soldier on but cant be too far from the toilet today lol.
    PS….not hungry

  6. The trick to this is not to cut carbs out drastically. Many people go crazy limiting themselves to 20g of carbs when your body is used to hundreds. The key to success is to slowly cut back on carbs until your body reaches 20-25g tolerance.

  7. I have learnt a lot from this explanation. I am feeling some of the symptoms. I have a terrible headache for which I take Tylanol. I hope to get out of this state quickly. Iam seeing results from the low carb diet.

  8. How do I know if I have keto flu or real flu or allergies? The keto test strips say I only have a small number of ketones. So, does that mean I can’t have keto flu? One weird symptom I rarely get with flu or allergies is I am very light-headed when I stand up.

  9. For me it is a little different, I stopped eating Bread, rice last year and ofcourse sugar. Then I stopped most of the potatos and pasta. Maybe on of the once a week. Everything fine! Then last month a tried the 5 day water fast, used some salt every day, Keltic salt. The last day at the end I started to feel like having a flu. Before I started the fast, I have to mention, I was in full Keto. So 2 hours before the 5 days ended, I stoped. It took 16 hours to feel better.
    Last week I have tried again. Now the 3th day I became sick, no power, realy bad. I continu 24- hours, but the I stopt. After now 2 days, slowly I star to feel better. What is the reason for this?? I am still in Ketosis

  10. I’ve only bee doing the Sroldiet for six days. I have lost seven pounds and felt fine until tonight. I woke up aching all over my body feeling cold. I mean really aching! I’ve never had the flu but I imagine it’s like this. I literally lived on sweets and carbs. So I’m sure that’s it. I craved water when I woke up like this and I understand that’s normal. I’m not giving up!

  11. Hi Jel, within the first 2-4 days of beginning a keto diet, a common side effect is known as the “ketosis flu” or “induction flu” because it mimics the symptoms of actual flu. We recommend to stay very hydrated and increase your salt intake. Also be sure you’re eating enough.

  12. Hi Dawn, common symptoms of keto flu are headaches, tiredness or lack of motivation, lethargy, brain fog or confusion and irritability. If you experience this, we recommend to stay very hydrated and increase your salt intake. Also, be sure you’re eating enough.

  13. Thank you for this vast amount of specialised information. I am delighted (with a natural degree of excitement) to have found your Perfect Keto site.
    A few years ago I sampled the benefits of intermittent fasting but I failed to read any connection with the Ketogenic lifestyle, so I continued ignorant of such.
    Recently, I experienced a lengthy and debilitating bout of a winter virus and decided that I either consider my health as my priority or I probably would not survive another winter.
    As I also take full responsibility for my health and understand the law of attraction, it was not a surprise to me to find the internet stacked with Youtube Keto information when I started to search. One site led to another.
    But I was surprised to find Perfect Keto with its comprehensive knowledge and professional approach to this powerful health subject.
    I have, of course, not finished my reading (study) of your pages and did not know if this was the correct place to put a comment (sorry about the length of it).
    I simply wish to say a sincere thank you for helping me to transform my life (an ongoing process) by sharing your knowledge.
    My gratitude to the internet expands.

  14. Hello. I guess I have had the keto flu now for almost 3 weeks. I have never had body pain/soreness like this in my life! OMG! I will never cheat again. Hope it subsides soon.

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