5 Causes of Keto Flu (And Remedies Too)

5 Causes of Keto Flu (And Remedies Too)

5 Causes of Keto Flu (And Remedies Too)

Posted 2 years ago

Brian Stanton

Brian Stanton

Author and book writer

Tony O’Neill, PT, DPT, MSc, RDN

Tony O’Neill, PT, DPT, MSc, RDN

Scientific Reviewer

Expert Approved

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 19

  • Maksbetterhalf

    Maksbetterhalf 6 months 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 3 months 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 4 months ago

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

  • AwesomeKetone420460

    AwesomeKetone420460 8 months 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 8 months 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

      • OutstandingRadish919059

        OutstandingRadish919059 7 months ago

        Try sugar free Reece’s for a fix

    • FortuitousMacadamia956703

      FortuitousMacadamia956703 9 months ago

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

      • EvaElisabeth

        EvaElisabeth 3 months 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 9 months ago

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

      • MarvellousCauliflower394996

        MarvellousCauliflower394996 7 months ago

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

      • BlithesomeCauliflower641220

        BlithesomeCauliflower641220 8 months ago

        Me too!

      • KiriKat

        KiriKat 8 months ago

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

    • BlithesomeRadish324410

      BlithesomeRadish324410 9 months ago

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

      • PropitiousRadish468286

        PropitiousRadish468286 10 months ago

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

        • FavorableMacadamia190058

          FavorableMacadamia190058 10 months ago

          This is such helpful information. Thank you!!

          • Suzette

            Suzette a year 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 5 months 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 a year ago

            Thank you very very informative

            • RemarkableMacadamia906566

              RemarkableMacadamia906566 a year ago

              Thank you for this article. It was very informative.