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.



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 bar
  • 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.


#1 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.

#2 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.

#3 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.