What is the keto flu or low carb flu and what to do about it?

Keto flu symptoms, mitigation and getting over excess carbohydrates

Any major dietary or lifestyle change has the potential to cause discomfort or lets face it, even mess you up for a bit. This is sometimes referred to as a ‘flu’. It’s the most common time during which people will quit their dietary or lifestyle shift as many simply feel they are unable to function without significant carbohydrates and snacking throughout day.

Here we’ll discuss the major downside to starting a ketogenic diet or a low carb one, and how to minimize the discomfort often accompanying this adaptation period.

Like most people you’ve probably spent 20 – 60 years feeding your body a significant amount of carbohydrates and much of them from poorly chosen overly processed sources.

Your cells, organs, central nervous system and brain have all adapted to it through hormonal and metabolic responses normally running in the background. Switching fuel sources, like eating less carbs and more fat, is likely to throw your body and brain for a loop.

To be clear, the “keto flu” label is a bit of a misnomer. It’s more akin to carbohydrate withdrawal symptoms resulting from a shifting hormonal states and imbalanced electrolyte adjustments that are along for the ride. Regardless, this buzz term is in the general consciousness now so we might as well keep using it for now.

Before diving into the details, keep in mind that the following four books should teach you nearly everything you need to know about low carb and ketogenic diets, including how to handle the keto flu. The rest of the relevant science is dispersed amongst hundreds if not thousands of papers only a search away on PubMed. If you want to ask questions about it or be part of our community please visit Ask BreakNutrition.


The trials and tribulations people encounter during the induction phase are unpredictable, but usually not too severe. They can range from nothing at all, to mild discomfort and mental fog, all the way through to full blown flu-like symptoms.

For example, the keto flu may involve nausea, fatigue, headaches, cramps, diarrhea etc. In severe cases, high blood pressure and arrhythmia can manifest.

It is wise to make an effort to reduce stress levels during this adaptation phase. Furthermore, exercise performance may suffer for a couple of days or weeks, but this is nothing to worry about. It’s a well-known phenomenon and is not indicative of long-term issues [1].

All it requires is acknowledging that exercise performance will probably suffer whilst the body adapts to using more fat and less carbs. See our post about high-intensity training and low carb diets for more.

It is worth noting that we have a diverse population of bacteria, viruses and other critters in our guts, so any major dietary or lifestyle change can likely disturb our gastrointestinal system and thus toilet habits in the short to medium-term.

The flora and fauna in our guts is commonly referred to as our gut microbiota and it is worth exploring in terms of dietary individualization another time. For now, understand that there’s nothing inherent about ketogenic diets per se that can cause issues such as gastrointestinal distress.

Odds are, it’s your unique and adorable snowflake metabolism taking its sweet time to adapt. Please know that in all-but rare metabolically deranged cases, everyone can adapt to a ketogenic diet or a low carb diet.

Unsurprisingly, there appears to be a reasonable correlation between the dieter’s previous lifestyle and severity of flu-like symptoms. If you’re a person already eating a higher fat and lower carb diet, the more likely you are to embark on a ketogenic diet or merely a low carb one with little fear of discomfort.

The induction phase of a diet typically lasts a few days to a couple weeks, at which stage the symptoms dissipate and energy levels return – usually with a vengeance!

Carbohydrate Addiction in keto flu 

No need for hyperbole here, the point is recent studies [2] are comparing the effects of carbohydrates (typically processed or sugar-laden ones) on the brain to various stimuli which are addicting and dependence forming.

These carb sources engender troublesome food-reward responses which Robb Wolf explores well in his book Wired to Eat [3].

We won’t go into that stuff here, just understand that you may be fighting what seems like unconquerable urges and cravings to start with. Once you understand that food, like other drugs, can either cause or exacerbate addictive behaviors, you can formulate effective strategies to avoid them as well as set appropriate expectations about self-control that may bubble up.

There are a few different ways to approach carb restriction, which effectively entails overcoming an addiction. There are different approaches to succeed in the induction phase:

  • Cold Turkey

    • It’s self-explanatory really. Jump into the deep end and learn to swim – just drop carbs as low as possible (0 – 50g a day) and eat as much fat to quell hunger.
  • Gradual reduction or substitution

    • Depending on your current lifestyle, you might choose to drop the carbohydrates by 10g a day and increase the fats to satiation and satiety [4].
  • Gradual Elimination

    • Each week remove another carbohydrate source. For example:
      • Week 1: Best place to start is soda, switch out for sugar-free diet versions, also halve the sugar you add to your coffee or tea.
      • Week 2: Then remove any of the daily desserts and sugary snacks – typically cakes, muffins, pastries and chocolate bars.
      • Week 3: Say goodbye to the starch monsters – pasta, pizza, packets of crisps and most stuff that comes in packets and boxes.
      • Week 4: Wave goodbye to your breads, rolls and potatoes.
      • Week 5: Hopefully by now most of your sugar cravings have subsided and you’re down to <100g of carbs a day. If you are significantly overweight, it’s not unlikely to spontaneously drop anywhere from 5 – 20 lbs without much difficulty.
      • Last step in the induction phase, if you wish to go lower, is to see if you can can handle going zero carb for a week, to really kick off ketosis. This means eliminating whatever minor “healthy” sources might still be lingering, like fruit and “sneaky” carb sources such as sauces for instance. Lower isn’t necessarily better, but aiming for zero carb can make your first foray into ketogenic diets less complicated.

Here is a small infographic about how to drop the carbs (feel free to share ?):

Keto flu as a symptom of the Induction phase

On a “normal” diet there are many people who eat a lot of processed foods, which by and large, are fortified with salt. 75% of salt consumed by Americans comes from processed and restaurant food, not the salt shaker [5].

A ketogenic diet in its basic form mostly revolves around meat, fish, nuts and non-starchy vegetables, so when transitioning from a normal to a ketogenic diet, people spontaneously reduce their salt intake radically.

This reduces water retention [6]. In other words, you become less bloated. Furthermore, lowering insulin levels and thus increasing insulin sensitivity can signal the kidneys to discard excess water [7].

For this and other reasons, you also tend to increase your water consumption, with the end result being lower water retention on top of increased water intake. This can be a big double-whammy, flushing a lot of electrolytes out.

Electrolyte imbalance – particularly sodium, potassium and magnesium deficiency – is the most common factor in the transitory flu-like symptoms. There is a laundry list of symptoms that deficiencies are associated with – all the way from sneezing to death – so it’s important you keep these levels in check.

Don’t worry though, your body is extremely good at letting you know when something’s up. It’s not as if you’ll develop some lifelong debilitating critical organ damage because you didn’t pay attention to a muscle cramp or mild headache that one time. Basically, don’t obsess, the stress will wear you out more than a mild short-term deficiency mineral deficiency.

To mitigate these symptoms it is usually recommended to increase salt intake, as this will help to counteract the initial water weight loss that occurs at the start of a low carbohydrate diet. Staying in the range of 5 – 7g of salt per day, about twice as much as the CDC’s official guidelines [8], may be necessary depending on your body weight and a few other factors. It can be exciting for a first-timer on a ketogenic diet to see up to 5kg (10lbs) just disappear off the scale in the first week despite eating more energy-dense foods to satiety.

However, if it’s at the expense of feeling like crap, then it’s best to slow things down and let your body adapt.

You’re already switching fuel sources, losing some electrolytes and embarking on a not insignificant lifestyle change, so don’t add severe caloric restriction on top of it all (even though fat-loss may be your long-term goal).

Especially in the induction phase, eat enough to feel full and don’t skimp on the sodium which and other minerals like potassium and magnesium. Remember, get your sodium from the salt shaker, not from processed or restaurant foods.

Now that you’ve got your fluid management under control, keeping an eye on the other electrolytes and minerals isn’t as big an issue in the short term. Nevertheless, it’s still worth supplementing potassium and magnesium – at least in the first few months.

You can either seek out supplements in the form of tablets or you can acquire it in the form of a homemade broth (or bouillon).

How much should I supplement to manage the ketu flu?

It’s not all that complicated, no need to go into huge detail here, even though there are entire books dedicated to this. The general consensus among low carb experts is you’re aiming for something like this every day, initially:

  • 5g of Sodium (salt)
  • 1g of Potassium (use “Lo Salt and similar brands that are about 2/3 Potassium and 1/3 Sodium)
  • 300 mg of Magnesium

Practically speaking, this simply means lightly salting your meals to taste and when making sauces, use generous helpings of sodium and potassium, as well as taking a Magnesium tablet with or after dinner. Avocados.

The best natural way to obtain these is in a cup of bone broth, which is dead easy to make. It comes down to a little simmering of beef/lamb/chicken/fish bones for 12 to 24 hours, and drinking it as a soup.

Bone broth delivers these and many other great nutrients aplenty, and in a readily bioavailable form. Just google broth recipes.

Otherwise, the soup section of your supermarket should have stocks and bouillon cubes available. For the latter, just check there’s enough minerals in it and that they don’t come replete with a host of unnecessary ‘flavoring’ and sugar.

Pro-tip: potassium and other important nutrients are lost in the water of boiled veggies and drippings of cooked meat, so remember to use them in your sauces [9].

The magnesium story is really complex and confusing as to which versions are best for bioavailability, the short version is typical cheap magnesium supplements are in the oxide form, and generally these aren’t absorbed that well and will mostly just be a laxative.

What you want is something that’s chelated which in non-sciencey terms means it’s bound to a protein and helps your body to absorb and use it efficiently. This is called making it more bioavailable.

Magnesium citrate will probably get you the best bang-for-your-buck [10]. It’s well absorbed, but may have a mild laxative effect in some sensitive people. Magnesium (bis)glycinate is typically a bit more expensive, although not much, and it’s absorption levels and lack of gut issues makes it worth it for some people. Magnesium bisglycinate is a top-tier choice in this regard [11].

When it comes down to it, magnesium bisglycinate and magnesium citrate are the best options for people trying out a ketogenic diet or are simply going low carb.

Then what?

Once you are feeling consistently good, which could take a day or a month, it may be worth dropping the supplementation to see how you feel and reassess. If need be, make the adjustments slowly.

As already mentioned, we don’t need to stress every day about whether our “levels” are right. The at-home monitoring technology for this is non-existent yet. Simply by eating quality foods and eliminating the worst offenders (flours and sugar)  should take care of most of that. Ultimately, you cannot medicate or supplement away the effects of a poor diet, but you can decide to focus more or less on eating well so as to minimize the need for supplements and medication.

A good bone soup from your typical land animals, once or twice a week, a small portion of liver now and then, eggs as often as desired, and oysters, mussels and other seafood when you can should easily cover most of the holes in your nutrient profile.

Other resources

If you’re concerned about the health ramifications of limiting “essential” carbohydrates and consuming more fat, then read Nina Teicholz’s book The Big Fat Surprise [12]. Truly a must read.


  • Refined starchy carbohydrates are the flours used for pastas, cakes, cookies, thickeners etc. have addictive properties. Reducing or stopping your consumption of them may induce withdrawal symptoms akin to a flu – hence the name “keto flu” or “low carb flu”. This is transitory and nothing to be alarmed about.
  • Depending on your personality and physiology, you may find it easier to immediately stop consuming refined starch carbohydrates or gradually reduce them. The opposite may be true for someone else. Whichever strategy you choose, don’t be too hard on yourself if you struggle with feelings of guilt or other negative emotions – addiction is as real with food as it with drugs.
  • During the induction phase and medium-term, you may find it helpful to supplement daily with 5 – 7g of salt, 1g of potassium and 300mg of magnesium. These are approximate figures requiring individualization.

30 comments On What is the keto flu or low carb flu and what to do about it?

  • This is the most helpful discussion of the electrolyte issue that I have seen.

  • day three after dropping carbs and sugar cold turkey, and I am urinating about every hour or 2 while drinking tons of water, constantly in a state of hazy confusion, dizzy and wobbly on my feet, dropped five pounds in 3 days, and I’m not sure if this is good, even normal, or if I’m about to die.

    • I feel the same way…today is day 4 for me and yesterday I had a horrible migraine and today can barely function. I have zero energy and no desire to eat anything. It literally feels like the flu. I too have lost 4 pounds since monday which is great but I don’t know if how I am feeling is healthy.

      • Salvatore Castellano

        Right there with you guys. I’m a week in and feel lazy as ever. My past few workouts have been the worst of my life =[ with absolutely no energy. Going to stick it out another week or so.

        To note, I did drop carbs cold turkey.

        • Hi Salvatore,

          good! this means you’re going through carbohydrate withdrawal, meaning your getting AWAY from those bad foods, now granting you the opportunity to replace them with good foods that will nourish you. this is temporary. if you’re finding it hard, try 3 things: (1) supplement salt (and magnesium and potassium) (2) sleep early & long (3) change your exercise routine such that it’s less stressful during your adaptation phase.

          Best of luck!

    • Hi Aisham,

      I’m not a medical doctor so if you’re worried please see one. i also don’t know if you’re on meds, diabetic, what your blood markers are etc. so it’s not possible to advise you specifically. however, brain fog is expected as is fatigue. these reactions are typically symptomatic of someone going through carbohydrate withdrawal. so you should keep it up, making sure to hydrate, take in magnesium, potassium, supplemental salt and to feed your system with good quality protein and fat. this should allow you to get through it.

  • I am so over this! I’m day 10 & have been feeling like crap for 4 days now. My heart will randomly race, unbelievably dry mouth no matter how much water I drink. Constant headache, I’m as weak as a kitten (I have to drag myself out of bed!) Sweating like it’s 40+ degrees. I’m emotional & also using the toilet excessively! It really does feel like withdrawals. I know it will all be worth it, or so I’m told lol but I’m really struggling 🙁 I am so glad I found these blogs & to know that it’s not just me struggling. I really hate feeling like this & can’t wait for it to get better!

    • Hi Kiri,

      I’m not a medical doctor so if you’re worried please see one. Just checking up on your progress – email me at [email protected] if you need some assistance. Or contact me via the Drift pop-up.

      i also don’t know if you’re on meds, diabetic, what your blood markers are etc. so it’s not possible to advise you too specifically. make sure to hydrate (but only to thirst), take in magnesium, potassium, supplemental salt and to feed your system with good quality protein and fat. this should allow you to get through it.

  • Hey Raphael, great write up! I definitely find it convenient to supplement, have you checked out keto-lytes which can help with keto flu? https://www.ketoshop.com/products/keto-lytes-electrolyte-and-keto-flu-support

    • Hello Michael,

      Thank you. Yes the keto-flu can be helped with supplementation of minerals like NaCl, Mg, K and Zn. I’m not familiar with your products so I’ll have a look. We’re interested in selling products that can help people transition into their new diet or improve their nutritional status, especially as related to to low-carb and ketogenic diets. However, we’re very cautious about working with people who push claims that their products cannot support – I hope you understand how cautious we are given the states of the supplement industry and field of nutrition science.

      Nevertheless, if there’s information about your product and company you think I should know about please let me know by email raphael[at]breaknutrition.com

      Cheers Michael!

  • Day 4: horrible metallic sensation in my mouth, I feel nausea, I want to keep eating just to get rid of the sensation…I do try to curve the eating, though. I’m not sure if I dropped any pounds (I don’t want to feel the deception). Does the metallic taste wane?

  • I am on day 3 and feel very nauseated today. I have only lost 1 pound so far which I am sure is ok but I do not feel good at all. I am going to stick it out. I just drank some beef broth so hopefully that will help! Thanks for the great tips and its good to know that this is normal.

  • I am on day 3 and am so glad I found this site and info! It helps to read others comments and know that what I’m feeling is “normal”. I’ve had a headache for 2 days, little dizzy, lethargic, feel hungry but nothing sounds good and several bowel movements per day. I feel a little achy like the flu. I’ve heard of “keto flu” so I looked it up and came here. I don’t have any supplements appears I need to get some! Also, I rarely add salt to foods (except bad foods like fries and tortilla chips so that’s out). I quit processed carbs and sugar cold turkey but am still having some fruit which has sugar (berries) and LOTS of veggies. Thank you for providing this info!!

  • Joe Rogan has an amazing Podcast. But I think he is dead wrong about Keto being healthy(at least for the majority of apes)
    Google the “negatives” of this Keto diet thing. It aint encouraging! I tried this Keto diet for 5 days(I am a very healthy/active 39 year old man). On day 3 I looked like I was dying of a deadly Virus; suffered from: Headache, nervousness, anxiety, depression, weakness, anger, lethargy, pale skin, acne, 10 lbs weight drop etc, etc & etc.
    I finally asked a couple friends if they knew about this diet. I also queried a lot of websites(in other words, I stopped cherry picking only positive articles). This diet is only recommended for a very small percentage of the talking apes. It fucks up the rest of us. We are supposed to eat Carbs; not the center aisle grocery store stuff-healthy carbs!
    So my semi-educated and lab rat linked opinion is avoid this diet. Life is hard enough and so many people already deal with mental issues-dont add flames to that fire. Ironically, many believe that this diet will ultimately help save people mental distress; garden variety depressions and all the fun ailments that this digital age has plagued a society of inherently social apes.

    • Hello, been on keto for 2 months, lost 30 pounds and Yes, I did go through keto flu but kept on track. I feel wonderful despite having type 2 diabetes. I am off all bp meds, cholesterol meds and insulin. I am doing this lifestyle along with the supervision of my doctor. Yes, it works and I eat healthy carbs, they are called Vegetables. Do it with a doctor, you won’t be sorry.

    • Hi Irving,

      I have to disagree with your contention that ketogenic diets are unhealthy for us per se. You can certainly be on a ketogenic diet that is unhealthy. I’ll give you a few examples; it could be too low in calories, it could be nutrient poor, it could include industrialized foods that just so happen to hit the macros and it could also simply be adpoted too infrequently to ever give the person sufficient time to get through the adaptation phase.

      That being said, you seemed interested in the evolutionary perspective, whether or not this is compatible with our species (if I understand you correctly). I wrote about this here http://breaknutrition.com/ketogenic-diets-in-human-evolutionary-history/. I encourage you to follow up the references I use. My view is that the metabolic status of ketosis is one all humans are in to some degree of other, whether it is as breast feeding infants, whether it is when intermittently fasting, or because of post-exercise glycogen depletion, of because temporary weather patterns killing off vegetation (forcing humans to rely on what we could hunt). It’s perfectly natural to be ‘in’ ketosis and to be ‘out’ of it.

      A well-formulated ketogenic diet already has clinical data supporting its utility for certain mental health issues. I discuss this with a Harvard educated MD psychiatrist Dr.Ede in a recent podcast http://breaknutrition.com/episode-22-dietary-insanity-dr-ede/.

      I like Joe Rogan very much and am happy he’s getting ‘the word out’ about ketogenic diets because many people stand to benefit. That being said, he does get quite a bit of the science wrong about the diet. But he’s not malicious when doing so.

      Lastly, I would simply suggest that if you couldn’t do the diet for more than a few days then there are 2 possibilities, 1 much much more likely than the other. (1) you are seriously insulin resistant and addicted to carbohydrates so you’re suffering from a particularly severe form of the keto-flu or (2) you have a rare genetic mutation in fatty acid metabolism.

      I would put my money on (1). Ironically, if this is the reason then you’d stand to benefit all the more to get fat-adapted. FYI this doesn’t imply being keto always, far from it – but it does mean periodically restricting food (fasting) and/or carbohydrates.

      Best of luck to you Irving!

  • Thought it might be helpful to post my reaction. Found this article because I’m lacking energy the last 4 days. No other symptoms and I quit carbs cold turkey 2.5 weeks ago, without initial transition problems either. I’ve always drank a ton of water so that hasn’t changed. Sure it’s just from my lack of electrolytes and so I’ll do a better job of getting those. With all the other comments of people having serious “flu” symptoms thought I’d post for people having a less tough time transitioning! I’m eating this way to get processed carbs out of my life – won’t worry so much about good carbs as in fruit and some veggies. I absolutely know I’m one of those people that is addicted to carbs! Like eat twice as much as my husband, be stuffed, and still want to eat more. Those feelings are totally gone!

    • Thanks for giving us your side of things.

      Drinking to thirst is really important because some people tend to ovedo the water and further flush out precious electrolytes, made all the worse if not supplementing with them.

  • Pingback: 6 Things That Happen to Your Body When You Go on a Ketogenic Diet – Out of Shape Runner ()

  • Been eating keto clean for about 3 weeks or so. I have not been targeting macros but have just eliminated all processed foods, sugars, etc adding organic grass-fed meats and healthy local small-farm fresh eggs. I admit to starting most days with one cup of homemade bulletproof coffee using salted grass-fed butter and a quality coconut oil, organic heavy cream and sometimes a little bit of unsweetened cocoa powder. I am highly insulin resistant but not yet diabetic. My fasting glucose levels are always between 100-104 and my A1C is in the non-diabetic range. I am taking metformin due to my insulin resistance. I’m considered obese per my BMI and the doc wants me to drop body fat and add lean muscle. I’ve noticed if I SEVERELY limit my carbs for more than 3 days, I’m laid flat out, my husband hovers checking me for fever, I don’t want to eat, I get chills, diarrhea, etc but it goes away within 24 hrs or so. Years ago, I eliminated salt from my diet using only small amounts of sea salt, and after doing this for years, my labwork proved I was deficient in iodine. So I once again salt my food and take kelp tablets (nasty pond water fish tank stinky pills) until my levels come back up. I drink warm bone broth that is very low sodium so I add my own salt. It’s also fat free, so I add a small bit of butter to it, too. Overall, I feel SO MUCH BETTER, my body doesn’t ache like it used to (I also have pretty bad fibromyalgia). I include plenty of avocado, pumpkin seeds, cashews, and greens (spinach and kale) to my diet. But my one problem is not ever actually feeling hungry. Many times, my clue that I need to eat is feeling run down or weak. Then it will dawn on me that I haven’t eaten for several hours. I drink plenty of water, but I never feel hungry anymore.

    • Hi TerriH,

      ‘several hours’ (assuming that’s less than 10?) is not a long time to go without feeling run down. If you’re still feeling run down you should address that. I’d suggest dropping the bulletproof coffee, getting in more sodium 4-7g/day depending on need/body weight, supplement with the right Potassium and Magnesium, and make sure the bulk of your food is quality animal protein. Veggies are fine as long as they don’t displace too much meat and you don’t suffer gastrointestinal issues or other adverse reactions from them.

      Drink to thirst 😉

  • I found this extremely helpful thankyou.
    Currently on just day 1 going cold turkey off carbs and augar and feeling extremely ill. Nice to know its normal.Wow how addictive are these nasties!
    I am always an oats for breakfast person but wanted some low carb /keto breakfast ideas.I wondered if anyone had some they could share and inspire me with? Thanks!!

  • I’m feeling really nauseous. I had to break down to eat crackers and ham and bean soup to help my nausea issuehow will this step me back. I’m still nauseous.

    • this is a common experience, one the co-founder of this website has gone through too – so fear not!

      what counts is following our advice and making sure all your other ducks are in a row

      – sleep
      – stress
      – movement (not exercise, but at least some walking and not being too sedentary)

  • I am curious how the Atkins Diet differs from the Keto diet. Can anyone shed some light on it?
    Thank you.

  • Do you have a higher res image of the infographic? It would help my friends and family ease in into cutting carbs.

Leave a reply:

Your email address will not be published.