Everything to Know About Keto Flu

Written by Sara McEvoy
on March 10, 2019

Got an Instagram account or a television? Then you've probably noticed how the keto diet is taking the health and fitness world by storm these days.

We'll argue this is for good reason. The ketogenic diet—which comprises high-fat, low-carb and moderate protein foods—has decades of research backing its safety and efficacy for helping people lose weight, improve blood lipid profiles, maximize energy and mental focus, and even manage drug-resistant epilepsy.1,2,3

But as effective and beneficial as keto is, there are aspects of this diet that aren't quite as, well, awesome, for lack of a better term.

Take keto flu, for instance. In this article, we're going to talk about what it is, why it happens, and how to get rid of it. 

Woman With Keto Flu

What Is the Keto Flu? 

Keto flu—also known as carb flu—is a sign you're going through carb withdrawal and a potential unfortunate side effect of starting a ketogenic diet. It's essentially your body saying, "WHOA, hold up," in response to a sudden and drastic decrease in dietary carbohydrates. 

You see; your body has gotten used to using carbs as its primary fuel source for the majority of your life. As you force your body to primarily use stored body fat for fuel instead, the transition period may be a little rocky, at least until you've been doing keto long enough and your body becomes used to your new diet (aka "fat-adapted"). 

Keto flu typically affects people within the first one to two days after switching to a ketogenic diet, and it can persist for about one to two weeks. A lot of this depends on individual characteristics, including how many carbs a person was eating before the switch. 

Top 5 Symptoms of Keto Flu

Keto flu doesn't affect everyone the exact same way, and some people can transition to a ketogenic diet without getting any sort of flu-like symptoms at all.

But if you notice any of the following issues within the first week to two weeks of adopting your new keto lifestyle, rest assured you're likely dealing with keto flu (and don't worry; it's normal and beatable—more on this in a second): 

  1. Muscle cramps, weakness and headaches
  2. Sugar cravings
  3. Brain fog and irritability
  4. Insomnia
  5. Dizziness

How to Get Past Keto Flu

Using stored body fat for fuel is something your body will likely enjoy doing and will do well once it's adapted to your new way of eating. But kicking the carbs can be tough, and while unpleasant, keto flu is generally considered a normal part of this transition. 

Fortunately, it IS possible to mitigate the effects of keto flu and get over it more quickly. Follow these tips when you're just starting out with the low-carb life: 

  1. Eat more fat. Dietary fat is super satiating and can help you overcome the super normal sugar cravings you may be feeling right now. 
  2. Drink more water. Carbs are stored in the body as glycogen molecules, which bind to water. Since eating fewer carbs equals less glycogen, water tends to be excreted from the body faster in the early stages of keto. So drink up (especially if you're experiencing diarrhea or constipation). Aim for at least half to two-thirds your body weight in fluid ounces per day. 
  3. Add in electrolytes. Try adding a pinch of Himalayan sea salt to your water or supplementing with a high-quality magnesium supplement, which can ease muscle cramps. 
  4. Eat more fiber. Fiber helps your digestive system function smoothly—so chow down on things like leafy green veggies, chia seeds and hemp hearts.
  5. Get enough sleep. Poor sleep might just be the best way to muck up your health and hormone levels, especially if you're going through keto flu. So improve your sleep during this transition period by minimizing caffeine intake, avoiding super strenuous exercise, and establishing a relaxing bedtime routine (no, that three-part documentary about serial killers is probably not the best pre-bedtime ritual). 


If you're trying keto for the first time, don't give up on the diet if you notice keto flu symptoms cropping up. People who follow the ketogenic diet successfully typically say they look, function and feel better than ever. 

Just remember: We're not doctors, and we don't play ones on the internet. If you're making any significant changes with your diet or exercise routine, it's a good idea to chat with your physician first. 

Want some higher quality fat in your life? Be sure to check out our range of keto-friendly, paleo-friendly and vegan-friendly nut butters that will help you say buh-bye to your keto flu. 


This article was written by: Sara McEvoy

Sara McEvoy, PT, DPT is a licensed and board-certified doctor of physical therapy. She earned her degree in 2011 from Boston University. Sara is also a professional freelance writer and copywriter. She researches and writes almost exclusively within the health and wellness field. 



Written by Sara McEvoy

Published: March 10, 2019