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Coronavirus or Keto Flu: How To Tell Them Apart


If you’re just starting the ketogenic diet, you may experience temporary flu-like symptoms. A lot of people get them during the first couple weeks of eating low-carb. 


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These symptoms are called the keto flu, and they happen because your body is still learning how to burn fat for fuel instead of carbs.

Keto flu is nothing to worry about — it happens to most people who start a keto diet. It’s harmless, and it goes away as soon as you’re in ketosis. 

But keto flu has some similar symptoms to the novel coronavirus (COVID-19), which is (at the time of this article’s publication) a global pandemic.

How do you know whether you have keto flu or coronavirus? 

This article will cover the common symptoms and side effects of both the keto flu and coronavirus, how to tell which one you have, and what you can do to get better. 

Keto Flu Symptoms: Side Effects of Starting a Keto Diet

On a standard high-carb diet, your body burns mostly carbs for fuel. But when you cut out carbs and switch over to a high-fat diet like keto, your body no longer has access to carbs. 

As a result, it switches over to burning fat for fuel — it breaks fat down into ketones, little units of energy that your cells use as a power source. 

If your body isn’t accustomed to burning fat as its main fuel source, it can take a few days for it to get used to the switch. During that time, you may experience the keto flu — a collection of flu-like symptoms. 

A new study published in the journal Frontiers in Nutrition searched online forums for people starting a ketogenic diet, then asked them whether they experienced keto flu. Common symptoms include[*]:

  • Headache
  • Fatigue
  • Nausea
  • Dizziness
  • Brain fog
  • Carb cravings
  • Rapid weight loss (usually water weight — your body releases water when you stop eating carbs)
  • Gastrointestinal discomfort and/or diarrhea
  • Dehydration

The study found that keto flu symptoms usually peaked within the first week of keto, and went away after a couple weeks. 

Let’s take a look at how keto flu compares to coronavirus symptoms. 

Coronavirus Symptoms: How to Know if You Have COVID-19

COVID-19 is a new strain of coronavirus, a flu virus that rapidly spread across the world, triggering a global pandemic. 

Coronavirus has a high survival rate, especially for people older than 10 and younger than 70. 

However, coronavirus spreads quickly and easily, so if you think you have it, self-isolation is essential. Social distancing in general is a good idea until the pandemic passes — it will decrease the transmission rate and help things get back to normal more quickly. 

Coronavirus has the following symptoms, which may appear 2-14 days after exposure[*]:

  • Fever
  • Dry cough (little to no mucus production)
  • Fatigue
  • Gastrointestinal discomfort and/or diarrhea
  • Headache
  • Nausea
  • Shortness of breath

There are also more severe coronavirus symptoms. If you have any of these, you should seek medical attention immediately:

  • Difficulty breathing
  • Pain or tightness in the chest
  • Confusion or inability to get up
  • Bluish lips or face

As you can see, there are a few overlapping symptoms between keto flu and coronavirus. 

Keto Flu or Coronavirus? How to Tell Which One You Have

Keto flu and coronavirus share a few symptoms, but they also present fairly differently. 

If you have a fever, cough, or shortness of breath, it’s likely coronavirus or another flu virus — keto flu doesn’t have any of those symptoms. 

Conversely, if you’re experiencing strong carb cravings, dehydration, or rapid weight loss, you likely have keto flu. 

If you have a runny nose and are coughing up mucus, you have the common cold.

But what if you’re in the middle, with shared symptoms? 


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Shared Symptoms of Keto Flu and Coronavirus

Overlapping symptoms of both keto flu and coronavirus include:

  • Fatigue
  • Headache
  • Gastrointestinal discomfort and/or diarrhea
  • Dizziness
  • Nausea
  • Brain fog

If you have these symptoms, it may be difficult to tell what’s going on with you. 

Don’t Hold Your Breath: There is No “Simple Self-Check” for Coronavirus

A body of text recently went viral on social media, suggesting that Taiwanese doctors and the Stanford Hospital Board recommend a simple self-check for coronavirus. 

​The text suggests that you hold your breath for 10 seconds every morning. If you can hold your breath without issue, you don’t have coronavirus. 

It turns out that’s not true[*]. Stanford Healthcare explicitly addressed the recommendation, saying that: “a widely distributed email about COVID-19 that is attributed to a ‘Stanford Hospital board member’ contains inaccurate information.”

There’s no easy way to test for COVID-19 at home, and this kind of misinformation is dangerous. 

What to Do if You Think You Have Coronavirus

If you have shared symptoms between keto flu and coronavirus, your best bet is to talk to your doctor, or to go into a hospital for coronavirus testing. 

However, at the time of this article’s publication, hospitals are already overwhelmed. Hospital space should be reserved for  the young and elderly, or for people with life-threatening symptoms like trouble breathing, persistent chest pain, and severe confusion. 

Coronavirus isn’t life-threatening for the vast majority of people. If you just have mild flu symptoms, the Center for Disease Control (CDC) recommends calling your doctor or healthcare professional, instead of going straight to the hospital.

In addition, follow these basic rules to stay healthy and prevent coronavirus from spreading:

  • Wash your hands regularly
  • Practice social distancing. Stay at home, only going out for essentials, and try to stay at least six feet away from other people. 
  • Eat a healthy diet to support your immune system and prevent flu infection. If you’re already sick, a healthy diet may help you recover. 

Boost Your Immune System with a Keto Diet

If you want to boost your immune system during the coronavirus pandemic, the keto diet is an excellent choice. 

Research from Yale University shows that mice eating a keto diet had a higher survival rate when infected with the flu, compared to mice eating a higher-carb diet[*]. 

Keto was especially effective at protecting the lungs, and it blocked inflammasomes, immune system activators that damage your cells during infection. 

Keto is great for your immune system, and is a strong choice if you want some extra insurance against the flu virus. 

This beginner’s guide to keto has everything you need to start a keto diet today. 

What to Do if You Have the Keto Flu

If you have the keto flu, the first thing to do is relax. 

The keto flu is normal, and it’s nothing to worry about. It will go away on its own within a few days. 

That said, it can be unpleasant, and you may want to get rid of it more quickly. Good tips to get rid of the keto flu are:

  • Drink plenty of water. You want to replenish all the water your body is getting rid of as it switches to burning fat. 
  • Double down on salt and electrolytes. You lose electrolytes with water, which can contribute to dehydration. If you want to make things easy, Perfect Keto Electrolytes are made specifically to help you through keto flu. 
  • Eat lots of fat. Don’t worry about calories until you’re past the keto flu. You may also want to keep keto snacks around to manage your carb cravings. 

Final Thoughts on Keto Flu and Coronavirus

At the time of this article’s publication, there’s an international coronavirus pandemic. Many countries and states have a quarantine in effect, and there’s a lot of widespread panic. 

In these trying times, it’s important to stay calm. The best thing you can do to protect yourself and others is to stay isolated at home. Doing so will curb the virus’s spread, making things return to normal much more quickly. 


Join 90k+ people who are losing weight with Keto Kickstart, our doctor-developed program designed to give you real weight loss results.

Don’t hoard food or supplies — just take enough to cover your needs. Eat well, exercise, wash your hands, take care of your loved ones and your community, and wait for this to pass.


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