If you’ve explored how to start a keto diet for weight loss, you may be concerned about “the keto flu”, one of the most common side effects of the keto diet. Don’t be! It’s totally avoidable, and temporary if you do experience it. In this article, I’ll tell you everything you need to know about keto flu and answer all your questions, including:
What’s the keto flu? Typical keto flu symptoms and signs of keto flu When keto flu starts How long keto flu lasts What causes keto flu (5 top reasons!) The most important part: 7 effective keto flu remedies and how to avoid keto flu altogether!
What Is Keto Flu?
Keto flu refers to flu-like symptoms that can happen when you transition into the keto diet. As your body shifts its primary fuel source from glucose and carbohydrates to ketones and fat, it can take your body some time to adjust to this metabolic change. Think of it as carb withdrawal. The keto flu is not actually the flu and is not contagious, but it gets its name because some of the symptoms are similar to the flu. Unfortunately, the medical community has not formalized exactly what is keto flu (*); in fact, PubMed, the library of indexed medical research journals, does not have a single result referring to this phenomenon. But, you can still recognize all the most common symptoms and apply well known keto flu remedies to combat or prevent it.
What Does Keto Flu Feel Like?
The name “keto flu” is somewhat of a misnomer. It’s actually quite different from what you’d experience with an influenza virus. Although keto flu does cause headaches, dizziness, fatigue, cramps, and muscle pain like the “real” flu might, you should not get a fever, chills, vomiting or respiratory symptoms. If you experience any of these, it’s best to consult with a doctor, as the cause is likely unrelated to a ketogenic diet. What keto flu feels like and the specific signs of keto flu will vary from person to person, but there are some common ones to watch for.
Signs Of Keto Flu
Your keto flu symptoms may vary, but here are some of the signs of keto flu (*):
Headache Dizziness Fatigue or tiredness Restlessness or irritability Brain fog, poor concentration, or confusion Lack of motivation Nausea Insomnia Impaired coordination Sensitivity to heat Sugar cravings Muscle soreness, cramps, spasms, or weakness Stomach pain, bloating, constipation or diarrhea
Don’t let this long list scare you! Here is why there isn’t a need to worry about these:
What Causes Keto Flu?
In a nutshell, keto flu happens because your body is adjusting to the new metabolic state of ketosis and reduced carb intake. If you’re interested in the science, there are several primary keto flu causes:
1. Electrolyte Imbalance
Electrolyte imbalance is the primary cause of the keto flu. Electrolytes are minerals that conduct electricity when dissolved in water and are necessary for critical body functions. The regulate the amount of water in your body, pH levels, moving nutrients into cells, moving waste out of cells, and making sure your nerves, muscles and brain work properly (). When you restrict carbohydrates, your body produces less insulin, causing your kidneys to flush out excess water and sodium (). In order to maintain the balance between sodium and other electrolytes, your kidneys will also release extra potassium, calcium and magnesium. Without enough sodium, potassium, calcium, and magnesium in your body, you experience signs of keto flu.
2. Dehydration
When you eat carbohydrates, your body stores the extra as glycogen in the liver, where they are bound to water molecules. Restricting carbohydrate intake depletes this glycogen, which allows you to burn fat – but it also means you are storing less water, making it easier to get dehydrated. (*) The aforementioned effect of reduced insulin levels increases dehydration further. So, it’s important to drink enough water — Mayo Clinic recommends 91 ounces of water daily for women and 125 ounces for men, though this includes water from your food. But if you drink a ton of water without replenishing electrolytes, you will dilute the concentration of electrolytes in your body even further and possibly make your keto flu worse. This is why it’s important to address both together.
3. Fuel Source Adjustment
When you eat carbohydrates, your primary fuel source is glucose. When you severely restrict carbs, your body switches to using ketones (from fat) for fuel instead. These are two completely different metabolic processes. Your body can handle both carbs and fat for fuel, but if you’ve been eating a Standard American Diet (or any high-carb diet) for a long time, it’s likely that your body is more accustomed to glycolysis (breaking down glucose to release energy). So, it may just need a little practice when switching to the new metabolic pathway, ketogenesis (breaking down fat into ketones and using those for energy). During this adjustment period, you may need to actively seek out a keto flu cure, which is explained below.
4. Sugar Withdrawal
Numerous studies have shown that sugar is habit forming (*, *). If you are used to consuming a lot of sugar, switching to a keto diet can come as a shock and lead to withdrawal symptoms, including cravings, anxiety, depression, irritability, insomnia, cognitive issues, and more. The effects of sugar withdrawal can compound any keto flu symptoms stemming from electrolyte imbalances, dehydration, etc.
5. Other Deficiencies
In general, switching to a ketogenic lifestyle is a great thing. The healthy fats, low carb vegetables, unprocessed meats, eggs, and other whole foods are nutritionally light years ahead of processed, packaged foods that you may be replacing. However, just like any diet, you can get the wrong idea. If all you eat is meat (or other protein), cheese, keto desserts, and low carb bread (as great as they are!), you may end up with deficiencies in vitamins and other micronutrients.
Keto Flu Symptoms And What They Mean
If you’re wondering, “what are the symptoms of keto flu?”, I have the full list above, but I’m also going to break down the symptoms caused by the deficiency of each of the major electrolytes commonly impacted by the keto flu. Many of these are similar (you need all of them and they work together!), but there are some differences. Still, these lists can help you identify which deficiencies you might have.
Keto Flu Symptoms Caused By Sodium Deficiency
Headache Dizziness Fatigue or tiredness Restlessness or irritability Brain fog or poor concentration Lack of motivation Nausea
Keto Flu Symptoms Caused By Magnesium Deficiency
Fatigue or tiredness Restlessness or irritability Brain fog or poor concentration Lack of motivation Insomnia Muscle cramps, weakness, spasms or soreness Stomach pain, bloating, constipation or diarrhea
Keto Flu Symptoms Caused By Potassium Deficiency
Dizziness or low blood pressure Fatigue or tiredness Nausea Numbness or tingling Heart palpitations Depression Muscle cramps, weakness, spasms or soreness Stomach pain, bloating, or constipation
When Does Keto Flu Start?
For the average person, keto flu hits within the first 1-3 days of starting a ketogenic diet. So even though “how soon does keto flu start?” is one of the most common questions I get about this temporary side effect of keto, the good news is you’ll know pretty quickly if you’re going to get keto flu or not.
How Long Does Keto Flu Last?
On average, the keto flu lasts for about a week. It usually peaks around 3-4 days in. However, how long keto flu lasts varies from person to person, and can be anywhere from a few days to a few weeks. It should not be longer than that. Keto flu symptoms will start to dissipate once your body becomes adapted to burning fat for fuel, but there are things you can do to make them go away faster.
Does Everyone Get Keto Flu?
No! Not everyone who starts a keto diet gets the keto flu. It depends partially on your metabolism (or metabolic flexibility – your ability to switch between carbs and fat for fuel) and genetics, but there are plenty of factors you can control. In fact, you can avoid keto flu. To do so, you need to understand what causes keto flu (see the section on that above!) and then take steps to prevent keto flu from the beginning (I’ll show you how below!).
Do You Get Keto Flu Every Time You Start Keto?
Hopefully, if you’re starting a keto lifestyle, it will be for the long term. That being said, we’re all human and things happen, so people often ask me whether they’ll experience keto flu again if they re-start after a period of not being in ketosis. This varies from person to person. Some keto dieters become very efficiently fat adapted and don’t get keto flu again if they cheat and then resume keto. This depends on your metabolic flexibility, as mentioned above. Often times, people restarting keto may experience mild signs of keto flu, but they are not as severe as the first time. Or you might not experience them at all as your metabolic flexibility improves. I highly recommend that you read my tips below for how to avoid keto flu altogether. Why go through it when you don’t have to? You can avoid keto flu the first time… and every time if you do have a slip-up.
Is Keto Flu Dangerous?
The keto flu is unpleasant, but generally not dangerous. People with kidney issues or low blood pressure may be affected more, due to the diuretic effects of the diet and (temporarily) reduced electrolytes. Some people think that the keto flu is a sign of ketoacidosis, a life-threatening condition in which excessive ketone levels build up in the blood. Fortunately, ketosis does not cause ketoacidosis, and despite their similar names, they are completely different. The latter is caused by a prolonged lack of insulin, usually from unmanaged diabetes. Electrolytes are important for our bodies to function properly, though, so the sooner you can get them in balance, the better.
How To Avoid Keto Flu
Knowing the signs of keto flu is great and all, but if you’re going through it, what you really need to know is how to cure keto flu, right?! Fortunately, you don’t have to just suffer and deal with it. I’ll show you how to get rid of keto flu quickly – and how to prevent it in the future. You don’t have to go through it just because you’ve decided to follow a keto lifestyle. I’ve compiled all the best keto flu remedy methods, whether you already have it or just want to avoid keto flu altogether. Here is how to prevent keto flu from the start:
1. Replenish Electrolytes (The Best Keto Flu Remedy!)
Getting enough electrolytes on a keto diet is the single best thing you can do to beat keto flu. In general, here is how much of each you need daily:
Sodium – 4000-7000 mg per day (that’s 2-3 teaspoons of salt per day!) Magnesium – 300-600 mg per day Potassium – 3000-4700 mg per day
If you’re just starting to look for a keto flu remedy to try, start with electrolytes – and start with getting them from food. Check below for what to eat for keto flu to replenish these electrolytes, as well as supplement options just in case you absolutely need them.
2. Drink Plenty Of Water
As mentioned above, a ketogenic diet causes a lot of water loss in the beginning, which can leave you dehydrated. Ironically, dehydration can actually lead to bloating and water retention, as well as dizziness and fatigue (*). TIP: Keep a bottle of water near you all the times to encourage drinking frequently. I love this bottle that has time markers, so that I can stay on track for the day! Aim for 16 cups of water per day (a gallon), but listen to your body’s signals and don’t overdo it. The goal is to reempt your thirst. Don’t forget to replenish electrolytes as you drink water, to avoid diluting their concentration in your body even more.
3. Ease Into Keto Gradually
You don’t have to start keto cold turkey. The keto macro calculator will show you the optimal macros for you on a keto lifestyle, but starting slowly is a great way to avoid keto flu.
To ease into keto gradually, start by cutting refined sugar for a few days or a week Next, cut starches (wheat, rice, potatoes, etc.) From there you can progress to a low carb diet (see the comparison of a keto vs low carb diet here), without restricting carbs enough to be in ketosis all the time. Once you feel comfortable eating low carb, progress to a ketogenic diet.
If you are already experiencing symptoms, one keto flu remedy would be to eat some moderate carb, nutrient-dense foods, such as extra vegetables or berries. Even if you go over your carb limit, it’s worth it if it gets you to stick with the lifestyle. You can reduce further once you feel better.
4. Eat Nutrient Dense Foods
Just because you are limiting carbs, that doesn’t mean that’s all there is to it. In addition to macro goals, the goal of the keto lifestyle is to eat clean, whole foods, so that we also get a wide range of micronutrients. In particular, getting enough (low carb) veggies is absolutely crucial – check the keto food list for ideas!
5. Eat More Fat & Calories
If you are not eating enough, this can cause some symptoms similar to keto flu. Be sure to eat enough that you aren’t hungry. Remember, the primary fuel source on a keto diet is fat, so you need to add enough to keep you satisfied and to help you adapt to burning fat for fuel. Resist the urge to make your diet both low carb and low-fat, which will just put your body into starvation mode. You’ll be hungry, miserable, and are bound to run into the telltale signs of keto flu. As you increase fat, watch the type of fat. You may need to watch your medium chain triglycerides (MCT’s), such as coconut oil:
If you have abdominal pain, you may need to ease into MCT’s slowly to avoid stomach issues. Balance them out with long chain triglycerides, such as olive oil or avocado oil. If you can handle MCT’s without a problem, try increasing them because they will get you into ketosis faster. (The liver metabolizes them very efficiently.)
6. Exercise (Gently)
If you notice an initial decrease in exercise performance when you start keto, don’t despair. This is temporary and usually resolves itself by week 4 of a keto lifestyle. (*, ) Even if you feel tired, don’t skip exercise altogether! Try less intense activities, such as yoga or walking, because these already often use fat as a primary fuel source. And, exercising can help improve your body’s ability to switch between the metabolic processes for burning fat and sugar, meaning you avoid keto flu ().
7. Sleep More
Sleep is important no matter how you’re eating, but if you’re already fatigued and struggling with keto flu, it becomes even more so. Lack of sleep can increase cortisol levels (cortisol is a stress hormone), which can amplify some of the same keto flu symptoms you’re trying to avoid (*).
What To Eat For Keto Flu
I’m a firm believer in using food as a keto flu cure whenever possible. Medications and supplements have their place, but always start with food first to see if that’s enough. Besides, you avoid any risk of overdose this way. Below are my favorite methods for how to treat keto flu with food.
Drink A Keto Electrolyte Drink
If you want to get your electrolytes from one place, a homemade keto electrolyte drink like this is a great place to start. It only takes 5 minutes to make, using common pantry ingredients. TIP: Don’t bother with store-bought sports drinks for replenishing electrolytes. Even if they are sugar-free, they actually have very small amounts of electrolytes compared to the food sources below, and won’t be enough to really make a dent.
Sodium Rich Foods For Keto Flu
Sodium is the most common electrolyte imbalance involved in the keto flu, and fortunately, it’s the easiest to incorporate into your food. Daily Sodium Goal: 4000-7000 mg per day Here are ways to get more sodium from food:
Salt – add it to everything! The goal is 4000-7000 mg of sodium per day, which is approximately 2-3 teaspoons of sea salt or table salt daily. This will vary slightly depending on the brand of salt you buy, though, because sodium content varies. If you can, get Himalayan pink salt.
REMINDER: Let go of any lingering “sodium is bad” concerns. Remember, your body is flushing out a lot of it when you eat keto, and depleted sodium is a big part of why you feel bad!
Bone broth – This is my favorite brand of bone broth – it tastes like you simmered it at home for hours, and has the same ingredients you’d use at home. A cup has 240mg sodium. Use code WHOLESOME for 10% off! Boullion cubes – Avoid ones with added sugar or MSG. I love these vegetable boullion cubes! Each cube has 2100mg sodium. Bacon – Naturally has plenty of salt added! I like to cook bacon in the oven on the weekend and use in recipes throughout the week. I get my bacon here (use that link to get a FREE package!), so that it’s uncured and sugar-free. One slice of bacon has 137mg sodium. Salted nuts – Try mixed nuts or these portion-controlled macadamia nut packs. A serving will only have 100-120 mg sodium, though, so don’t rely on it as your main source. Pickles + pickle juice – Make sure there is no added sugar! I like this brand or this brand. An ounce of pickles typically has 125 mg sodium.
Magnesium Rich Foods For Keto Flu
In addition to the more broad keto flu symptoms like headache and fatigue, magnesium is particularly helpful for insomnia, constipation, and cravings. Daily Magnesium Goal: 300-600 mg per day Here are some good food sources of magnesium:
Seaweed – This is the best source of magnesium from food! A one-ounce serving of dried agar seaweed contains 216 mg magnesium. Seeds – Hemp, flax, pumpkin and chia seeds are all great sources of magnesium. Hemp seeds are at the top (179 mg per ounce) – use them to make keto oatmeal. Pumpkin seeds are also excellent, at 150 mg per ounce. Nuts – Get out that almond flour (and browse my almond flour recipes)! Almonds and brazil nuts have the highest content, about 80 mg magnesium per ounce. Avocados – One of many reasons I love this superfood is it’s packed with magnesium! (See it in my logo?) One avocado contains 58 mg magnesium. Leafy greens – Each cup of raw spinach, kale, or collard greens has approximately 25-30 mg magnesium. It gets a lot more concentrated if you cook them.
Potassium Rich Foods For Keto Flu
Potassium has serious side effects if you overdose on it, so a whole foods based approach is best for this electrolyte in particular (*). Daily Potassium Goal: 3500-4700 mg per day Here are some of the best keto-friendly sources of potassium:
Potassium chloride – This is a table salt replacement (instead of sodium chloride), such as this one. Only use this if you already have enough sodium AND you are watching your intake to make sure you don’t go over 4700 mg potassium in a day. Just 1/6 teaspoon has 530 mg potassium, so it adds up fast! Avocados – An avocado has a whopping 974 mg potassium! Bone broth – In particular, this chicken bone broth has 530 mg of potassium per serving. Spinach – A cup of raw spinach has 186 mg potassium, which doesn’t sound like much, but you can easily have a few cups. And if the spinach is cooked, you’ll need much less for the same amount of potassium, since it shrinks so much. Broccoli – Broccoli has 288 mg potassium per cup! My favorite simple way to serve it is sauteed broccoli with garlic. Mushrooms – A cup of raw mushrooms has 223 mg potassium, yet only 1.6 g net carbs. Leafy greens – The amounts vary, but many leafy greens are rich in potassium. For example, just one cup of cooked Swiss chard has 961 mg. Zucchini – One of my fave low carb veggies is also one of the best potassium sources, at 325 mg per cup. Try making zucchini boats or zucchini noodles! Beef or pork – 3 ounces of beef has 270 mg potassium, while the same amount of pork has 360 mg.
Keto Flu Supplements
Try to get your electrolytes from food sources whenever possible. However, if you find that you can’t get enough, you can add a supplement. If possible, consult with your doctor before beginning any supplement regimen, especially if you have impaired kidney function.
Electrolyte Blend For Keto Flu
If you want to know what to take for keto flu to see improvements quickly (and food just isn’t cutting it), these are my favorite keto electrolyte supplements specifically designed for a keto diet. They include a balance of sodium, potassium, magnesium, calcium, and chloride, without being so high in any of them that you risk dangerous levels.
Magnesium Supplements For Keto Flu
Often times, sodium and potassium are easy enough to get from foods, but magnesium is more difficult and you need only a magnesium supplement. Unfortunately, most magnesium supplements are sold as magnesium oxide, which is a laxative and has poor bioavailability (read: we don’t absorb much of it). Choose one of these magnesium supplements instead:
Magnesium glycinate – This form of magnesium contains glycine, which has a calming effect, good bioavailability, and no laxative properties. Magnesium citrate – Magnesium citrate can alleviate constipation and acid indigestion, is inexpensive, and has moderate bioavailability. Magnesium L-threonate – In addition to high bioavailability, this one has been shown to improve memory and cognitive function (). Bonus! Magnesium malate – This form of magnesium has the highest bioavailability ().
