The Keto Flu: Why It Happens and How to Get Rid of It
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The Keto Flu: Why It Happens and How to Get Rid of It

Flu-like symptoms can be a problem on the keto diet and may be a sign of serious deficiencies. Here's what you need to know about the keto flu.

How to Get Rid of the Keto Flu

The ketogenic diet involves changing your metabolism from favoring glucose from carbs to fat and ketones for energy.

And with this big metabolic change comes some potential side effects. Things like headaches, fatigue, and nausea can pop up in the first week or so of the keto diet. A phenomenon referred to as the keto flu.

The good news is — it’s temporary.

Keto flu is most prevalent when you’re transitioning into a ketogenic state. Once you’re fat-adapted, the symptoms disappear. Still, it’s good to know what you’re up against, plus how a few simple tips and tricks may help prevent keto flu symptoms.

What Is the Keto Flu?

The keto flu is a temporary collection of flu-like symptoms you might experience when trying to enter ketosis for the first time. It goes away once you become fat-adapted — within the first week or so of eating a ketogenic diet.

It happens because your metabolism needs time to adjust to running on fat instead of carbs.

Your body burns carbohydrates (glucose) for energy by default. When you drastically reduce your carb intake — like on a low-carb ketogenic diet — your body depletes your glucose stores and starts burning fatty acids for energy.

This metabolic switch can be tough on your body, hence the flu-like symptoms.

Keto Flu Symptoms

It’s not uncommon for keto beginners to experience the keto flu when they first reduce their carb intake. Common symptoms include:

  • Stomach pain
  • Brain fog
  • Dizziness or confusion
  • Nausea
  • Irritability
  • Diarrhea or constipation
  • Muscle cramps
  • Muscle soreness
  • Lack of concentration or focus
  • Trouble falling or staying asleep
  • Sugar cravings
  • Heart palpitations
  • Low energy levels

Symptoms usually occur within the first day or two of starting your new diet, and the severity and length of symptoms vary from person to person.

Some people don’t experience it at all, while others could experience it during the first week or longer.

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.

Keto Flu Causes

There are four potential causes of keto flu:

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

#1: Keto Adaptation

Your body has two primary energy processes:

  1. Glycolysis: burning glucose for energy
  2. Beta-oxidation: burning fat for energy

Keto-adaptation means adjusting to the process of beta-oxidation, or burning fat for energy.

The ability to switch between burning fat and burning glucose is called metabolic flexibility[*].

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 role. Some people are naturally more capable of handling the energy switch.

Takeaway: Adapting to ketosis is the main cause of the keto flu.

#2: Electrolyte Imbalance

When you radically decrease the amount of high-carb processed foods you were used to eating on the standard American diet (SAD), your body starts to lose water quickly.

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 grams of water).

When you go keto, your cells use up all that glycogen, which means that your water weight gets flushed out.

So now you’re losing both fluids and important electrolytes, which then causes dehydration and electrolyte imbalances.

This combo can cause flu-like symptoms like headaches, fatigue, and aches and pains until everything becomes balanced again.

During your transition, it’s crucial to replenish your stores by increasing your water intake.

You’ll also want to add back the minerals you’re losing (i.e., electrolytes such as sodium, magnesium, and potassium).

This will help ease the transition and ensure you’re still getting an optimal amount of the nutrients you’re losing through your urine.

Properly hydrating with extra water and electrolytes will help you prevent and reduce your keto flu symptoms.

Takeaway: Losing water and electrolytes when you’re transitioning into ketosis can trigger flu-like symptoms.

#3: Lack of Micronutrients

Another common trap many beginner keto dieters fall into is not eating enough micronutrients.

When you cut out certain 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 drastically reduce your carb intake and start eating primarily eggs and cheese to stay keto, you’re at risk of creating nutrient deficiencies.

To combat this, it’s essential to eat a wide variety of nutrient-rich keto foods and stay healthy during your transition.

A diet high in these foods will cover your bases:

  1. Fatty cuts of grass-fed meat
  2. Coconut and cacao butter, as well as coconut, olive and avocado oil
  3. Nuts and seeds (including nut and seed butter)
  4. Poultry, fish, shellfish
  5. Veggies like alfalfa sprouts, broccoli, cucumber, cabbage, olives, spinach, Swiss chard, eggplant, asparagus, cauliflower, Brussels sprouts, spaghetti squash, etc.
  6. Full-fat organic dairy

If you’re short on time or always on the go, supplementing with micronutrients may be an easier option so you’re not missing out on essential vitamins and minerals.

Each scoop of this Perfect Keto Micronutrient Powder comes packed with pure, plant-sourced nutrition from 26 different fruits and veggies, helping you get a healthy dose of these important micronutrients without having to physically eat almost 30 healthy foods.

It’s also free of sugars, cheap fillers, and additives so you’ll never have to worry about any questionable ingredients kicking you out of ketosis.

Foods to Avoid on a Keto Diet

Speaking of, there are certain foods you should avoid on a ketogenic or low-carb diet. You’ll want to steer clear of packaged foods since these often contain chemical ingredients, which can prevent you from reaching and maintaining ketosis, thus prolonging your keto flu. Other foods to avoid on keto include:

  1. Grains like wheat, barley, oats, rice, quinoa, rye, buckwheat, and sprouted grains
  2. Beans such as kidney, black, pinto, lima, and chickpeas
  3. Most fruits, especially tropical ones like bananas, oranges, pineapples, papayas, and mangoes as well as apples and grapes
  4. Starchy vegetables including sweet potatoes, carrots, parsnips, potatoes, and corn
  5. Cane sugar, raw sugar, and high fructose corn syrup, as well as sweet syrups like honey, agave, and maple syrup
  6. Milk and low-fat dairy
  7. Factory farmed, conventional meat options such as grain-fed or highly-processed meats, farm-raised fish, etc
  8. Unhealthy vegetable oils like soybean, canola, corn, grapeseed, peanut, sesame, sunflower, and safflower
  9. Processed foods
  10. Artificial sweeteners
  11. Sweet alcoholic and non-alcoholic beverages

Takeaway: Micronutrient deficiencies can trigger the keto flu. Eating a nutritious ketogenic diet is key.

#4: Carbohydrate Withdrawal

Some studies suggest that sugar affects the brain in a way similar to addictive substances like heroin or cocaine[*] — consuming sugar provides the “feel good” hormone known as dopamine.

That’s why carb withdrawal can contribute to the keto flu. You’ll see this in the form of mood swings, irritability, cravings for sugar, and other adverse symptoms.

This is especially pronounced in people who eat more processed and refined carbs and sugars. People in this category also have more trouble adapting to fat burning, therefore they have a harder time losing weight.

But this doesn’t mean you should abandon ship.

If you’re experiencing these negative withdrawal symptoms, it’s a sign your body is getting closer to reaching ketosis and you just need to power on.

At this point the keto benefits really start to kick in.

Once the sugar and carbs are finally out of your system, you’ll start to lose weight and realize that after the initial discomfort, the keto benefits are well worth it.

Takeaway: Carb withdrawal can worsen keto flu symptoms, particularly if you’re used to eating high-carb, processed foods.

5 Steps to Get Rid of the Keto Flu

If you’re already experiencing the keto flu, take comfort in knowing this is temporary and there are things you can do to reduce or even eliminate symptoms during your transition to ketosis.

If you suspect you’ve been hit with the keto flu and you’re past the point of prevention, below are some things you can do to get rid of it.

How to get rid of the keto flu

#1: Stay Hydrated

As mentioned earlier, drinking extra fluids and staying hydrated should be your top priority.

The water loss that occurs at the beginning of a ketogenic diet needs to be replenished. The more often you do that, the easier the transition will feel.

Drink plenty of water throughout the day to help reduce symptoms like headaches, fatigue, or nausea that are often caused by dehydration.

Here are some easy ways to accomplish this:

  1. Keep a reusable water bottle near you, filled at all times so you can drink it wherever you are.
  2. Always drink when you feel thirsty, but try to catch it before thirst strikes.
  3. Drink most of your water during the day so you’re not waking up in the middle of the night for a trip to the bathroom.

Takeaway: Drink more water to get rid of headaches and fatigue.

#2: Replenish Electrolytes

On top of getting enough water, your next focus should be balancing your electrolytes.

You may not have considered your electrolytes before keto unless you were exercising vigorously or had too much to drink the night before.

The transition from using carbs for energy to using fat for energy will flush important electrolytes from your system.

And each person loses electrolytes differently.

Keep these general guidelines in mind to mitigate a potential imbalance:

  1. Increase your sodium intake. This will help counteract the water loss that happens when starting a keto diet and replenish sodium. Get your sodium from Himalayan pink salt instead of regular table salt.
  2. Supplement with magnesium. Low magnesium levels can lead to depression and insulin resistance, among many other issues, so it’s important to include this mineral in your diet. Some rich food sources of magnesium include hemp and pumpkin seeds, cooked spinach, halibut, cashews, salmon, macadamia nuts, avocado, and dark chocolate[*][*][*].
  3. Eat potassium-rich keto foods. Potassium is another key mineral that should be on your radar but probably isn’t. This electrolyte is involved in heartbeat regulation, muscle cramping, energy production, bladder control, and body temperature[*]. If you’re feeling any issues connected to these areas, consider adding more potassium-rich foods like avocado, Brussels sprouts, mushrooms, zucchini, and pumpkin seeds to your keto meal plan.
  4. Eat calcium-rich keto foods. Broccoli, leafy greens, chia seeds, sardines, and salmon are all packed with calcium. And bone health isn’t calcium’s only job. It’s also vital for blood clotting, muscle contractions, and good cardiovascular health[*].
  5. Take an electrolyte supplement. If you need instant relief, taking an electrolyte supplement will help replenish your levels faster than foods can. Check out the vitamin and mineral supplement guide for more information.

Takeaway: Keep your minerals in check, or take an electrolyte supplement to balance your electrolytes.

#3: Exercise

The type of exercise you do matters during your transition from burning carbs to fat.

Your exercise performance may temporarily suffer while your body is adapting to a higher fat and lower carb intake.

So while you probably won’t hit a personal record during this time, that doesn’t mean you should stay in bed.

Getting light exercise 2-3 times per week can help make your body more efficient at switching between carbs and fats for energy (i.e., metabolic flexibility), which helps decrease keto flu symptoms more quickly[*].

Low-intensity aerobic exercises — such as walking, swimming, or practicing yoga — are smart during this time since your body already uses fat as its primary energy source when performing this type of exercise.

Once your body gets through the transition, you should be able to resume your normal exercise routine.

Learn more tips on exercising while on keto.

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

#4: Increase Fats 

Since your body is no longer getting its energy from carbohydrates and sugars, it needs plenty of fat and protein for fuel.

This means you’ll need to make sure the calories you used to get from carbs are partially replaced by eating plenty of keto-friendly fats.

Some of those include:

  1. Grass-fed butter or ghee
  2. Heavy cream
  3. Coconut oil
  4. MCT oil
  5. Eggs
  6. Palm oil
  7. Cacao butter
  8. Extra virgin olive oil
  9. Avocados and avocado oil
  10. Goose fat
  11. Lard and bacon fat
  12. Pecans, macadamias, and walnuts
  13. Flaxseed, sesame, and chia seeds
  14. Fatty fish

Increasing your fat consumption while reducing your carbohydrate intake will help ease your transition since you’ll be pushing your body into using fats for energy.

Supplementing with MCT oil can also help you beat the keto flu by increasing your ketone levels, which can shorten your transition period.

If you find the keto flu persists 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 might be holding them back.

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

#5: Take Exogenous Ketones

Remember, one of the reasons you may have the keto flu is because your body is trying to create and use ketones for energy.

One way to help mitigate keto symptoms is to add exogenous ketones, or ketone salts, to your morning routine.

These energy molecules are the same ketone bodies your body naturally produces, in supplement form.

Supplementing will flood your system with ketones so you get some of the benefits of being in ketosis before you’ve even burned through your glycogen stores.

You can use exogenous ketones during your initial transition or anytime you want a quick boost of energy and mental clarity.

Takeaway: Supplement with exogenous ketones to help get keto-adapted more quickly.

How to Prevent the Keto Flu

If you’re just starting the keto diet and want to prevent the keto flu altogether, it can be easily avoided by following the steps below.

Steps to prevent the keto flu

#1: Follow a Nutritious Ketogenic Diet

One of the main reasons beginner keto dieters start to feel unwell on keto is the lack of proper micronutrients.

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.

To make your life easier, 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 keto dieters. 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 at night, try taking a power nap or two during the 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.

How to Remedy the Keto Flu

The ketogenic diet is a great tool for improving your health, aid weight loss, and help you feel 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:

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

Be Patient and Take Care of Yourself

Use the healthy tips above to help reduce symptoms and even avoid the keto flu altogether. Also keep in mind that if you experience any flu-like symptoms, they will subside. Just give it 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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16 thoughts on “The Keto Flu: Why It Happens and How to Get Rid of It

  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.

    1. 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.

  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

    1. 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.

  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. 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.

  12. 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.

  13. I started immediately hot/cold
    Aching all over. Sick to my stomach. Knee replacements ache.
    Chestheavy. Coughing
    Went to Dr she gave me antibiotic for viral flu.
    Starting reading more about the plan
    Yes Keto Flu

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