The aim of the ketogenic diet is to take away your body’s primary fuel source (glucose) and push it to burn fat instead for energy, breaking down your fat reserves into ketones to be used as fuel. This sudden transition from one biological process to another, along with a radical change in the types of food you’re eating, can cause side effects commonly known as the keto flu.
SEE ALSO: Signs of being in ketosis
In this article we’re going to discuss everything you need to know about it, including what causes keto flu, how to prevent it and how to treat the symptoms in case you get hit by it.
If you’re just getting started with keto then we recommend checking out our beginner’s guide to the keto diet, as well as these 7 tips for starting keto to make sure you’re doing keto right, and reducing the chances of getting keto flu in the first place.
What is keto flu?
Keto flu is the name given to some adverse effects you may experience on the keto diet, especially in your early days. It’s not caused by any viruses or bacteria, but it’s called “flu” because the symptoms can be similar. Some such symptoms include headache and diarrhoea  as well as feeling lethargic and tired.
The effects don’t last for long, and many people don’t experience them at all in their transition to the keto diet. If you do, it’s important to understand the underlying causes.
What causes keto flu?
1. Suddenly cutting carbs
You may have a rough time transitioning into the keto diet if your diet has been full of sugar and unrefined carbohydrates all your life. In the early days hunger and cravings for carby foods are going to be pretty strong.
This is because research states that our brain can perceive palatable foods the same way it sees drugs.
Addictive substances like some drugs can release dopamine, a hormone that makes you feel happy and causes you to repeat the behavior that made you happy. This is how people become addicted to things.
The same thing can happen when you eat sugary and oily foods regularly, especially if you have any food disorders . Your body doesn’t appreciate the fact that you stopped feeding it with something that makes you happy, and therefore you may experience some adverse effects as a result.
A study conducted by the state university of America found that highly processed foods and foods with a high glycemic index are more likely to cause food addiction. They also noted that these foods share the same characteristics as drug abuse .
Tiredness is the other big factor early on. In the early days after cutting out carbs, you’ll have taken away your main fuel source, glucose, which is easily used by your body and which it’s become used to having a constant supply of.
By cutting out carbs suddenly, your body will continue to use what reserves of glucose it has stored, in the form of glycogen in the muscles and liver. The problem is these reserves are pretty minimal and will run out in a day or so.
In the meantime, your body will be ramping up the breakdown of fats into ketones, to be used as a replacement fuel. If you’ve done keto regularly before, or regularly fast, this ramping up of ketone production may be quite quick and the transition from one fuel source to another quite seamless.
The problem comes if your body isn’t used to this transition and you find yourself in a situation where you’ve run out of one fuel source (glycogen), but haven’t really got the replacement (ketones) up and running yet.
When this happens you may find yourself feeling sluggish, and unfocused, and very hungry as your body wants some fuel ASAP.
The good news is, in a short space of time, if you stick to it and stay low carb, your ketone production will accelerate and these early tiredness symptoms will be replaced with a renewed sense of energy, hang in there!
2. You lose a lot of electrolytes
Have you ever wondered why people lose weight fast as soon as they start the keto diet?
It’s because when you drastically reduce your carb intake, your body will start using stored glycogen for energy before it switches to ketones. Each gram of stored glycogen is wrapped with roughly 3-4 grams of water .
In these early days you’ll be dropping a ton of water weight as you use up those glycogen reserves.
Along with the fast weight loss, you will also be losing a lot of electrolytes with that water via your urine, sweat, and bodily fluids.
These electrolytes are minerals that play essential roles in your health and wellbeing. Too much or too little of any of them can cause mild-serious consequences.
It’s very common in the early days of transitioning to keto to quickly deplete these electrolyte reserves, and this can be one of the main causes of the various flu like symptoms you get transitioning onto the keto diet.
There are three main electrolytes associated with keto flu symptoms:
- Potassium: mainly responsible for muscle contraction, and regulating fluid balance. It also has other health benefits, such as reducing the risk of cardiovascular diseases and osteoporosis.
- Sodium: plays a vital role in maintaining homeostasis and electrolyte balance.
- Magnesium: crucial for the functioning of more than 300 enzymes and helps regulate nerve function.
Symptoms: What does keto flu feel like?
Here are the signs and symptoms of keto flu for depleted levels of each of the three main electrolytes discussed above. If you find yourself experiencing any of these in the early days on keto then follow the tips to add more electrolytes back into your diet.
1. Potassium imbalance symptoms
The institute of medicine in Canada and the USA recommends 4700 mg of potassium per day for anyone over the age of 14. However, research states that most people in the United States are only getting 2700-2800 mg per day.
This means the risk of potassium imbalance is even higher for those who are on the ketogenic diet. Potassium deficiency begins when the potassium level in your blood drops to 3.5 mmol per liter. Anything between 3.5 to 5 mmol is considered the normal range, and it’s what most people go through .
Blood potassium level below 2.5 mmol is considered severe and life-threatening.
If you notice the following symptoms on keto, it could be an indication of low potassium:
- Leg cramps
- Weakness and/or paralyzed feeling in muscles
- Muscle twitching
- Rapid heartbeat
- Stomach cramps
- Mood swings
- Digestive problems
2. Sodium electrolyte imbalance symptoms
You’d never have to worry about sodium deficiency on a high carb diet because nearly all foods contain it. Table salt, e.g., sodium, so any food and beverage that has salt contain this mineral.
A 2016 research paper states that we need less than 500 mg of sodium for it to maintain homeostasis. However, a lot of Americans consume more than 3200 mg per day. Excess sodium intake also has adverse effects, such as the increased risk of cardiovascular diseases .
On the keto diet, however, you may experience the opposite problem: low sodium side effects.
This is because, as stated earlier, the ketogenic diet is diuretic, and you’ll be losing a lot of electrolytes via your urine and bodily fluids.
You might be running low on sodium if you experience the following symptoms:
- Brain fog
3. Magnesium imbalance symptoms
Magnesium is important for many vital functions in your body, such as protein synthesis, and nerve function. The daily recommended magnesium intake is 410 mg for men, and 360 mg for women.
However, research says that up to 68% of Americans don’t meet their daily magnesium requirements. One of the main reasons for this could be because processed foods contain less magnesium, and also because magnesium absorption rate decreases with aging .
Adding to that, being on the ketogenic diet may cause you to excrete more magnesium than you usually would.
You might need to up your magnesium intake if you have the following keto flu symptoms:
- Muscle cramps
- Mood swings (depression)
- Sleep problems
- Headache and migraines
- Irregular heartbeat
How To Get More Electrolytes On Keto
Quite a lot of keto-friendly foods are rich in electrolytes, so including one or more of them daily will help you stay on track.
A key tip is to make sure you’re adding plenty more veg into your diet when going keto.
A lot of people think the keto diet is all about butter, cheese, meats and dairy. That sounds appealing as people love those sorts of foods, but the truth is you really want to be starting with a base of green, non-starchy veg such as spinach, broccolli, kale etc, and adding fats and protein on top.
Doing this makes sure you’re getting a bunch of varied minerals and vitamins in addition to fats, which will really make like easier and help to avoid the electrolyte imbalances we’ve discusses.
What Keto foods are high in Potassium?
Include the following foods in your diet to make sure you’re getting an adequate amount of potassium.
- Swiss chard
4 easy ways to include them in your diet:
- Throw a cup of spinach in your egg omelet or scrambled eggs
- Egg or chicken salad with plenty of greens
- Try to add half/whole avocado to your diet each day
- Spinach egg muffins
What foods are high in Magnesium?
These foods will help meet your requirements for magnesium.
- Low carb nuts & seeds (almonds, macadamia, pecans, walnuts, and brazil nuts)
Five easy ways to get more magnesium:
- Grilled or baked fish with spinach and avocado
- Nuts and seeds as a snack
- Kale, avocado, and spinach smoothie with some unrefined salt
- Take magnesium supplement
What foods are rich in sodium?
Below are some easy ways to get more sodium in your keto diet:
- Bone broth: make a large batch that will last for a few days to a week.
- Cottage cheese
When does keto flu hit?
You may begin to experience keto flu symptoms within a few days of starting the ketogenic diet. Tiredness and hunger cravings will likely hit early on.
Some people assume they’re doing something wrong if they don’t experience any keto flu symptoms. However, it shouldn’t be seen as a sign of successful ketosis. If you take the right steps you should be able to minimise any negative experiences during your transition.
How long does keto flu last?
You can get rid of keto flu symptoms within 24 hours to a few days. Some people may take up to a few weeks to a month, but the key is figuring out early on what the likely cause is and dealing with that.
Can keto flu be prevented?
It’s possible to prevent keto flu symptoms by gradually decreasing your carb intake rather than jumping into keto right away. You can also try other tips discussed below, such as sipping saltwater throughout the day and drinking bone broth.
9 Best Keto Flu Reliefs
Below are some tips you could try for faster recovery from keto flu symptoms. Some of them may only take an hour or two to work like the saltwater tip, and some help speed up the recovery process.
- Increase your fat intake
In the early days it’s important to make sure you’re well fuelled up with healthy fats to give your body the best chance of transitioning quickly into ketosis.
A lot of people overestimate their fat intake and underestimate their carbs in the early days and don’t fully transition off carbs, prolonging many of the keto flu sypmtoms.
- Slow down your transition into Keto
You don’t have to go full keto day one, eating for less than 20g of carbs per day.
This sudden change is the primary cause for much of the keto flu symptoms, so if you’re experiencing these and can’t push through just yet, then ease off and aim for 50g of carbs per day instead.
Even though you’re eating slightly higher carb, do make the effort to cut out sugars and processed foods during this period for optimal results.
Whilst this may slow your transition into keto, and associated weight loss, if it helps you stick with things longer then this is a good first step before going full keto.
Once you’ve been comfortably eating a low carb diet around 50g carbs per day for 2-3 weeks you may be in a better position to try again dropping down to 20g and full keto.
- Sip unrefined saltwater
This is one of the first (and easiest) things you can do if you notice any low sodium symptoms such as headaches, brain fog, or nausea.
Saltwater is abundant in sodium. Mix half a teaspoon of unrefined sea salt or Himalayan pink salt into a glass of water. Sip it throughout the day with a few hours of gap between every two or three sips.
You mustn’t drink a large quantity of saltwater at once, as it may cause diarrhea.
- Keep physical activity low-moderate intensity
During this transition, how our body is finding and using fuel is critical and will impact what symptoms we experience.
For that reason in the first few weeks on keto it’s probably best to avoid overdoing physical activity, favoring long walks, yoga and stretching over sprints, long distance running and intense weight lifting.
Breaking a heavy sweat during this transition period is only going to speed the loss of electrolytes, as well as drain you of energy at a time when you’re not fully ready. Both of which will likely make your keto symptoms worse.
The good news is once you’ve adapted to the diet, after a month or more, you may find yourself with more energy than before, particularly for moderate level exercise and endurace type training.
- Make a large batch of soup or bone broth
Soups and bone broths are not just comfort foods that make you feel better, but they’re also rich in electrolytes. Making them in large quantities will make it easier to have them any time you want a quick boost of electrolytes.
- Have a keto smoothie with good fats
You don’t have to meet your daily fat requirement, but it’s important to remember the nature of the ketogenic diet. It’s a high-fat diet, and consuming more healthy fats will help with the production of ketones.
Try drinking a keto protein shake or smoothie with high-quality fats such as avocado or mct oil.
A word of caution about MCT oil
A lot of people try mct oil without doing any prior research on the dosage and side effects. It’s a high-quality fat that your liver can digest without the help of enzymes and use for energy.
However, you should never start with the maximum dosage of 2 tablespoons per day. This is the primary reason why many people experience diarrhea from mct oil. You need to start with half a teaspoon or one teaspoon for a few days to build tolerance and then gradually up the dosage.
- Drink coconut water (without added sugar)
Coconut water is an excellent source of electrolytes. It’s not something you might want to drink every day because it has 9-10 grams of carbs. However, it’s great for those times when you experience keto flu symptoms such as lethargy, headache, and nausea.
It can also be used as a rehydration fluid after a workout. One study compared the effect of fresh young coconut water and high carb electrolyte water after exercise in 8 male participants.
They found that the coconut water was better tolerated due to its naturally sweet taste and resulted in less nausea and improved rehydration .
- Take magnesium supplements
You may also benefit from taking a high-quality magnesium supplement on your keto flu days, and on the days when you know your meals didn’t have any magnesium-rich foods.
- Maintain water balance
It’s essential to stay hydrated, but it’s equally important to make sure to avoid overhydration. A reasonable target range is 2-3 liters of water per day as a minimum.
You might not need 3 liters of water a day if you live a sedentary lifestyle. On the other hand, you might need that amount or more if you happen to be more physically active and feel thirsty more often.
Set an alarm reminder to drink a glass of water every 2-3 hours if you’re someone who hardly drinks water, and drink whenever you start to feel thirsty. Letting yourself get too dehydrated is a surefire way to get headaches and lethargy.
The color of your urine is an excellent indication of your hydration level. A transparent urine color means that you’re over-hydrated, and deep yellow-orange indicates dehydration.
Check our guide on 6 ways to speed up weight loss on keto.
- Keto flu refers to flu-like symptoms you may experience on the keto diet, and pathogens do not cause it.
- It’s a result of sudden carb withdrawal and loss of key electrolytes (sodium, magnesium, and potassium).
- Keto flu can be prevented if you gradually reducing carb intake before going full keto and replenishing your electrolytes regularly using the tips discussed in this article.
- Keto flu symptoms usually go away within a few days. Please see your doctor if your symptoms show no sign of improvement after a couple of weeks if you’ve been dealing with electrolytes etc.