5 Causes of Keto Flu (And Remedies Too)

5 Causes of Keto Flu (And Remedies Too)

#1 Low Carb & Keto Diet App Since 2010

Track macros, calories, and access top Keto recipes.

Download on the App Store
Get in on Google Play

For a nontrivial number of people, the Keto diet comes with unwanted side effects. These headaches, cramps, energy drops, and GI problems are known collectively as Keto flu. 

Because of Keto flu, many folks quit Keto before achieving their health goals. 

If going Keto means I have to feel like THIS...no thanks! The weight loss and other benefits aren’t worth it. 

It’s an understandable reaction, but fortunately, eating a Keto diet needn’t doom you to a lifetime of symptoms. Generally, the Keto flu is temporary, especially when you understand what might be causing it. Then you can apply the proper remedies. 

That’s what today’s article is all about.

What Is Keto Flu?

The Keto flu isn’t a virus. It’s a constellation of symptoms linked to low-carb dieting, especially the early stages.

Keto flu symptoms include:

  • Headache
  • Weakness
  • Fatigue
  • Irritability
  • Insomnia
  • Muscle cramps
  • Diarrhea
  • Constipation

These symptoms tend to occur in the first few days of Keto dieting, but often they persist weeks or months into the diet. At the most basic level, the symptoms are a product of carb restriction. 

Hormonally and metabolically, a lot changes when you cut carbs. Blood sugar and insulin levels drop, fatty acids are broken apart and released from fat cells, and your liver starts burning fat and producing ketones.[*

It takes time to adapt to these changes, and it’s not always a smooth transition. Especially when you don’t account for the downstream effects of these changes, like higher electrolyte excretion.[*

With that in mind, let’s talk about what might be causing your Keto flu. 

5 Keto Flu Causes

The typical explanation for Keto flu is something like…”Your body needs time to adapt to using fat for energy”. 

This isn’t necessarily wrong, but it also doesn’t tell us much. Here are some more specific potential causes:

#1: The Brain Is Hungry

Normally, your brain runs 100% on glucose. But when you eliminate carbs, your glucose supply goes down, and your body starts making its backup brain fuel: ketones.[*

With ketones available, your brain needs much less glucose to meet its substantial energy demands. From an evolutionary perspective, ketones helped our ancestors stay energized and lucid during times of scarcity. 

But going from glucose to ketones isn’t like flipping a switch. In the first three days of Keto dieting, reduced glucose to the brain may cause Keto flu symptoms like fatigue and headache.[*

#2: Sugar Withdrawal     

It’s not crazy to call sugar a drug. Some research, in fact, suggests an analogy between the addictive properties of sugar and those of—believe it or not—cocaine.[*

The mechanism is interesting. By rapidly raising blood sugar and insulin levels, refined sugar stimulates the release of dopamine, a rewarding chemical that binds to your brain.[*] Every time someone eats a sweet, the reward pathway is triggered, and the addiction is strengthened.  

And the stronger an addiction gets, the more likely the addict will experience withdrawal symptoms. This is well-documented for other dopamine-driven drugs of abuse.[*]

To be clear, there’s no published data linking sugar withdrawal to Keto flu symptoms. But if someone was eating a high-sugar diet before going Keto, sugar withdrawal could be a legitimate concern.

 #3: Electrolyte Deficiency

Keto dieters must pay special attention to their electrolyte intake. Why? Two main reasons:

  1. Low-carb diets lower insulin levels, which increases excretion of electrolytes like sodium and potassium through urine.[*]
  2. The Keto diet restricts electrolyte-rich foods like fruits, potatoes, and salty snacks. 

In other words: Less electrolytes in, more electrolytes out. It’s a recipe for deficiency. 

And the symptoms of electrolyte deficiency (especially sodium deficiency) are eerily similar to what people call Keto flu.[*] Could these headaches, energy issues, cramps, confusion and insomnia be helped by eating more salt? In many cases, probably.  

#4: Dehydration  

Along with losing more electrolytes, Keto dieters also lose more water. The mechanism is similar: Low insulin has a diuretic effect.[*

The process of losing significant body water is called dehydration, and the symptoms of dehydration look a lot like Keto flu. We’re talking headaches, fatigue, cramps, etc. 

We’ll return to dehydration later in the article, because many people take the wrong approach. It’s possible, in fact, to drink too much water, dilute blood sodium levels, and worsen the problem. 

#5: Not Enough Fiber

Constipation and diarrhea are common Keto flu symptoms, and they probably can’t be explained by the causes above. 

That’s where fiber comes in. Dietary fiber is a form of carbohydrate that moves food through the gut, keeps you regular, and feeds gut bacteria that aid in digestion.[*

A lack of fiber may partly explain the GI issues linked to going Keto. When you eliminate fruit, whole grains, and starchy vegetables—you eliminate some of the best sources of fiber on the planet. 

Keto Flu Remedies 

Now that you’ve learned what causes Keto flu, the following remedies should make sense. If you’re low on sodium, for instance, the remedy is fairly obvious: Eat more salt. 

Here’s a list of Keto flu prevention tips:

  • Give it time. Transitioning your fuel system from sugar to fat may not happen overnight. Remember, your brain normally uses 100% glucose for energy, and it may take several days or more to comfortably switch to ketones. And if you’re dealing with sugar withdrawal symptoms, time is also your friend. 
  • Get enough electrolytes. To prevent electrolyte deficiency on keto, eat a diet rich in sodium, potassium, magnesium, and calcium. This can be accomplished by salting your food, drinking bone broth, and eating plenty of leafy vegetables. You might also consider a well-formulated electrolyte supplement. 
  • Drink to thirst. Thirst is a finely-tuned mechanism, honed over millions of years of evolution.[*] In most cases, drinking to thirst will prevent both dehydration and over-watering—both of which can cause symptoms. 
  • Eat low-carb veggies. If you’re having gut issues on Keto, play around with adding more spinach, kale, asparagus, lettuce, cauliflower and broccoli to your plate. These and other non-starchy veggies aren’t just good sources of electrolytes; they’re also high in dietary fiber.

  • Mind your macros. Eating a high-fat low-carb Keto diet signals your cells to burn body fat and produce ketones. But if you eat too many carbs (or not enough fat), you’ll likely have trouble adapting to Keto. You may get stuck in an uncanny valley in which you’re eating too many carbs to enter ketosis, but not enough carbs to satisfy your brain’s raging appetite for glucose. That’s why it’s essential to mind your macros in the early stages of Keto dieting. 

Macro tracking is easier than you think. Simply type out the foods you’ve eaten (3 eggs and 2 slices of bacon, for instance) and the Carb Manager app handles the rest. No tedious lookups or complex click-throughs. 

In the app you’ll also find thousands of recipes, customizable meal plans, a supportive community, and a bona fide Keto Academy to help you hit your health goals while avoiding Keto flu. See you there.

Comments 24

  • IneffableKetone631949

    IneffableKetone631949 10 months ago

    I must have this keto flu I feel awful I haven't eaten much vegetables so I just ordered a bunch of vegetables to be delivered tomorrow I want to go to super bowl so I hope it's just the keto and I don't have the flu I'm drinking tons of water I haven't eaten any salt so I'll solved everything in the morning I'm eating cheese now and I've got four bottles of water I'm drinking right now I don't know what else to do.

    • Gnebee

      Gnebee 2 years ago

      Pickle juice is amazing for the flu symptoms...and I'm not a pickle fan. That flu will kick your buns for about a week. Now to tackle the constipation...first try at bulletproof coffee (coffee, coconut oil and butter) will report results. Started Keto for bad IBSD and can stand to shed some weight. Is working great for IBSD but now on the other spectrum as my body adjusts.

      • Maksbetterhalf

        Maksbetterhalf 2 years ago

        I was wondering why my energy would just drop and now I know why. For my electrolytes could I drink a Powerade if I feel this way again?

        • EvaElisabeth

          EvaElisabeth 2 years ago

          Try bone broth, it's basically another word for soup stock. Easy to make from chicken or beef. I think Powerade is full of high fructose corn syrup which is basically poison for your body.

        • UpbeatArugula461594

          UpbeatArugula461594 2 years ago

          My weight loss Dr told me to drink Diet Lemon Ice Tea

      • AwesomeKetone420460

        AwesomeKetone420460 3 years ago

        I thought my headaches were allergies driven. I take allergy medication. Understanding this new process is something different but I believe if I stick with it it will be beneficial in the long run. My weight is 218 my goal is 170

        • AwesomeKetone420460

          AwesomeKetone420460 3 years ago

          I was wondering why I am feeling light headed in need for sugar and what I ate was horribly wrong and I sufferers for it 2 Reese’s cups. I’m hating my stomach right now! How do I get past this

          • jgbeck22

            jgbeck22 2 years ago

            I just got turned on to Atkins Indulge Peanut Butter cups. I eat 1 and it is only 1 carb. The other one I like is the Atkins Caramel Chocolate Nut Bar. I believe it has 2 or 3 net carbs. They are too good to be okay to eat. I have only been doing this for a few weeks so if someone reads this and knows a reason why we can't eat these, please let me know. You have to try them!

          • OutstandingRadish919059

            OutstandingRadish919059 2 years ago

            Try sugar free Reece’s for a fix

        • FortuitousMacadamia956703

          FortuitousMacadamia956703 3 years ago

          What is the best electrolyte supplement? With the sport drinks you get into the Sucralose problem. What is the best?

          • Gnebee

            Gnebee 2 years ago

            Pickle juice worked best. Cheap and easy.

          • EvaElisabeth

            EvaElisabeth 2 years ago

            Try bone broth, lots of easy recipes out there. We get whole chickens instead of buying chicken breast, wings, etc separate. the Buther breaks it down and gives us the carcass and we make the broth from that. If you don't need that much chicken buy a large packet of chicken wings and use those for the broth, cut up the wing a bit with a big chef knife or cleaver.

        • FortuitousRadish692457

          FortuitousRadish692457 3 years ago

          I’ve been on keto for two weeks. I’m in moderate ketosis by the keto stick and haven’t lost anything.

          • SuperAvocado985943

            SuperAvocado985943 9 months ago

            2.weeks.for me too, first week I lost 5 lbs. It's best to do measurements of your waist,bust, thighs etc. I know someone that went down 3 pant sizes and the scale still said she didn't lose weight. Good luck

          • MarvellousCauliflower394996

            MarvellousCauliflower394996 3 years ago

            I feel like I have been doing really good also. Minimal results. Trying not to give up

          • BlithesomeCauliflower641220

            BlithesomeCauliflower641220 3 years ago

            Me too!

          • KiriKat

            KiriKat 3 years ago

            Me too but minimal ketosis! I’m getting frustrated. I’ve been sooo strict. I don’t get it.

        • BlithesomeRadish324410

          BlithesomeRadish324410 3 years ago

          That explains why I feel like this, not too bad, will survive 😀

          • PropitiousRadish468286

            PropitiousRadish468286 3 years ago

            The headache is killing me...on my way to the store to buy electrolyte rich foods and broth.

            • FavorableMacadamia190058

              FavorableMacadamia190058 3 years ago

              This is such helpful information. Thank you!!

              • Suzette

                Suzette 3 years ago

                Thank you for the info… I believe this will help me… I sure hope so cause I can’t stand this constipation LOL

                • PropitiousArugula137122

                  PropitiousArugula137122 2 years ago

                  I bought NOW psyllium husk capsules, 500 mg, for intestinal health and to maintain regularity. I take 3 capsules with each meal. I buy these on Amazon. These are a game changer and really work. Once your colon is cleared out, you will go every day.

              • Ritan79

                Ritan79 3 years ago

                Thank you very very informative

                • RemarkableMacadamia906566

                  RemarkableMacadamia906566 3 years ago

                  Thank you for this article. It was very informative.