How Long Does The Keto Flu Last? (What The Science Says)

John Osborne
Feb 20 · 6 min read
Disclosure: Bear in mind that some of the links in this post are affiliate links and if you go through them to make a purchase I will earn a small commission at no extra cost for you.

Have you ever wondered how long the keto flu last (also referred to as the ketosis flu)?

Then you have come to the right place. In this article we will take a closer look at exactly what the keto flu is and how you can mitigate the flu-like symptoms.

So without further ado, let’s just jump straight into it.

What Are The Keto Flu Symptoms?

Side effects such as headaches, nausea, leg cramps and dizziness are all common side effects of getting into ketosis. So common that they are named “The Keto Flu”.

The side effects are usually easy to fight, and in this article I will show you the most common side effects and how to fight them so you can feel all the benefits of the ketogenic diet.

Your body is most likely getting used to eating carbohydrates by now which is why it’s important to slowly start switching to a more efficient fuel source — fat.

That being said, your body HAS to get used to it which is why it’s common to experience flu-like symptoms when we transition from burning sugar to burning fat as fuel. These are physiological changes that you can feel.

For example, you lose a large amount of fluid at first, and along with the fluid, you lose salt.

We need salt in all of the body’s cells, and salt deficiency is most often to blame for most of the symptoms of a keto flu. It’s important to note that the keto flu will usually go away after 4–7 days.

Try The Popular 28-Day Keto Challenge Here

The Most Common Keto Flu Symptoms Are

  • Headache, dizziness and nausea
  • Cramps in the legs
  • Palpitations
  • Getting out of breath easily
  • Constipation and/or diarrea
  • Bad breath

Keto Flu: Headache, dizziness and nausea

In the transition from a normal diet to keto, many people encounter the keto flu. It varies from person to person, but what is common to all is that it quickly passes.

As your body burns the last amount of carbohydrates you have on your body, in your sugar deposits in the muscles and in the liver, you will lose a large amount of fluid and electrolytes (salts). This can give you a feeling of nausea, headache, dizziness, minor cramps in legs and an increased fatigue. This condition can be explained by the lack of electrolytes.

If you experience any of these symptoms, you can test if it is due to salt deficiency in a simple way. Drink a glass of water with 0.5 teaspoon salt. If your symptoms disappear you know instantly that you need more electrolytes.

There are several ways to alleviate your symptoms. You can eat plenty of salt in your food or take a glass of warm boullion water in the morning. If you choose animal boullion, you will also benefit from other good substances such as collagen.

Salt is not just salt. There is a big difference between the quality of salt and how it affects you.

Via; Sand & Steel Personal Training

Ordinary table salt contains sodium chloride, which is what we refer to as salt. It is white, which is a sign that it is unclean. Pure salt is transparent and clear, and can have different colors (pink, blue, etc.) depending on the substances it contains.

Himalayan salt has a beautiful pink color from trace elements iron oxide. It has a fairly high content of iron, magnesium, potassium, chloride, phosphorus and potassium, and it has a known lower content of sodium than ordinary. salt has.

In addition to iron oxide, the salt also contains other trace elements that are important to our health, including flouride, selenium, copper, zinc and of course iodine.

Muscle cramps in the leg

It is very normal in the transition to ketosis to experience some minor cramps in the legs. This, in turn, is due to a lack of some specific electrolytes, namely magnesium, a salt that you also secrete.

If that doesn’t help with a shot of Himalayan salt, you can try a magnesium supplement, or hydro tabs, which give you the magnesium your muscles need.


When you do not consume carbohydrates, your body will automatically excrete some fluid, corresponding to approx. a few pounds of your body weight.

This happens because carbohydrates “bind” fluid in your body and because your body has a reserve of carbohydrates lying around. So it saves on a little carbohydrates, which saves on liquid and salt. When you lose these carbohydrates, you simultaneously lose the fluid and salt.

When your body has less fluid, the heart has to pump a little bit faster and maybe a little harder to get the blood circulating in your body. The body has a slightly smaller volume to do well with, and it is therefore natural to experience that the heart pumps faster or harder at times. This can be a new feeling for many, and especially if the feeling comes unmotivated, for example sitting or lying down.

If in any way you get chest pain or a severe feeling of shortness (it is ok to have to breathe a few extra times, as the heart pumps a little extra), seek medical attention.

Drink plenty of water and take in extra salt and you’ll be okay.

Try The Popular 28-Day Keto Challenge Here


Your digestive system, your stomach and your gut, are tasked with breaking down the food you consume, but they are also tasked with separating and re-adjusting the excess food.

If you lack fluid, your digestive system has difficulty performing its functions and therefore you may experience having constipation. A simple solution to this problem is usually to drink more water. Drink 2–3 liters of water a day during the transitional period to avoid constipation.

Eat high fiber vegetables to activate the intestinal system as much as possible. You can also supplement with 1 tablespoon of psyllium fiber in a large glass of water. This has been shown to have good effect for many.

Bad breath

Do you find yourself having bad breath? This is from the chemical acetone, which is created when you burn fat and ketones. This is a typical sign that you are well on your way to ketosis or already in ketosis, and while it is not fun to have bad breath it is only temporary.

It is a sign that you are doing well, and it usually goes away within a week or two as your body learns not to “leak” ketones through your breath and through your sweat.

There are some things you can actively do to combat your bad keto breath. You can make sure you maintain good oral hygiene, possibly use mouthwash, eat gum frequently, drink water and take your extra electrolytes.

If it doesn’t stop, you may be too far in ketosis (over 4 in ketone value), and should perhaps decrease this slightly.

That being said the keto flu can last a week or less but in extreme cases the keto flu can last up to a month.

Try The Popular 28-Day Keto Challenge Here

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