What to Do About the Keto Flu

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Dealing with ketosis adaptation symptoms?

Many people have been drawn to the keto diet as a natural weight loss solution. We’ve talked about keto before, it’s the low carb, high fat, moderate protein diet. So far, the evidence says it works for weight loss in the short term, but the jury’s still out on keto’s long term effects. 

Some folks have reported a number of undesirable side effects when first beginning the keto diet, called “keto flu” by those in the diet community. While it’s not as severe as its name might lead you to think, it can certainly be annoying. Wondering what to do about the keto flu? We looked into it so we could tell you!

What is the keto flu?

What is the keto flu?                  

As your body switches from burning glucose to burning fat as an energy source, you enter the metabolic state known as ketosis. As you are cutting out most if not all carbs, your cells and organs may experience “withdrawal” from carbs. The keto flu is a common name for these “carb withdrawal symptoms” that may appear 2-7 days after starting keto. 

What are the symptoms of the keto flu?

Symptoms include nausea, constipation, headaches, foggy brain, irritability, fatigue, and sugar cravings. These side effects vary person to person in severity and length, though they usually only last around a week. Some people starting the keto diet may never experience the keto flu, while others may have acute symptoms. Every body is different!

While the keto flu still hasn’t been recognized by scientific study, it’s a very popular topic within the health and diet communities. We do know that ketosis is a very real process that occurs in starvation, fasting, and low-carb diets, but its side effects have only been recorded anecdotally. 

What causes keto flu?

While we're still not sure what exactly causes keto flu symptoms, there are a number of theories:

  • Carb withdrawal
  • Sugar/processed food withdrawal
  • Lower blood sugar levels
  • Electrolyte depletion
  • Changes in hormone levels
How long does keto flu last?

What to do for the keto flu:

Soft exercise: You don’t need to overdo it at the gym while practicing the keto diet, but light exercise is a great way to mitigate some of the physical adaptation symptoms of ketosis. Opt for low-intensity exercises like walking, swimming, or yoga to boost your energy levels and relax your muscles.

Hydrate: Switching over to ketosis means you’re going to be pumping a lot more salt and water through your kidneys. As such, dehydration is responsible for a lot of the symptoms often attributed to keto flu. Make sure to drink water at regular intervals or whenever you feel thirsty. You’ll also be passing a lot of electrolytes and other salts, so don’t forget to replenish those as well to avoid cramps. 

Eat a lot of healthy fats: One of the pillars of the keto diet is replacing carb intake with fat consumption. When your body is in or entering ketosis, fat becomes your main caloric fuel source. Without enough calories, you may experience more symptoms of “keto flu.”

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Sleep hygiene: Our rest is delicate and crucial to our wellbeing. Switching up your diet can affect your sleep patterns, so make sure to support healthy sleep in other ways. Wake up and go to bed at the same time each day, avoid tv or phones for one hour before sleep, and minimize ambient light.

Don’t waste money on supplements: there are plenty of products promising to mitigate or eliminate ketosis adaptation symptoms. None are approved by the FDA, and you’ll be much better off taking care of your health naturally through proper exercise, sleep, and diet.


The keto flu is a collection of symptoms that may occur during the early stages of ketosis adaptation. These common side effects include nausea, headaches, lethargy, diarrhea, and sugar cravings. They aren’t debilitating, however, and can be reduced with proper sleep, hydration, and light exercise. 

The keto diet isn’t for everyone, and it’s important to know what you’re getting into before starting keto. Don’t forget to talk to a doctor before you start any new diet, or if you experience severe/prolonged side effects from a diet.