Keto Flu: Everything You Need to Know

The ketogenic diet has steadily increased in popularity. That it is grounded in natural processes has given the ketogenic diet widespread appeal. But, like anything else, the ketogenic diet comes with its own set of drawbacks. Keto flu is one of these drawbacks.

Because the ketogenic diet causes a metabolic change in the body, it often causes some side effects that are collectively referred to as the keto flu. Low carbohydrates and high fats can produce some unpleasant symptoms for some people.

While keto flu is generally a temporary condition, a small price you pay for the long-term benefits of ketogenesis, it is nevertheless difficult to deal with. Keto flu has stopped some people from continuing the diet.

The ketogenic diet is, in fact, a healthy way to lose weight and get fit. The problems arise when the body reacts to the central feature of ketogenic diets which is the metabolic state of ketosis. In most cases, keto flu is temporary as your body adjusts to ketosis.

This article will explain the metabolic and physiological processes that cause keto flu. We will explore the ways keto flu can happen and what people really mean when they talk about keto flu.

What Is the Keto Diet?

The keto diet has become one of the most important diet trends around because the way it works is to alter your natural metabolic processes toward losing weight. Rather than counting calories, the keto diet centers on reducing carbs while increasing fats. This dual focus results in lower blood sugar and insulin levels. The result is that your body turns to fats as a source of energy rather can the glycogens derived from carbs.

The keto diet shares some similarities with the Adkins Diet in that one of your main concerns is reducing or even eliminating carbs. It differs from Adkins in some important ways, but the main difference is that keto supplements the absence of carbs with fats.

By eliminating carbs, the body’s metabolic processes have to turn to a different energy source, in this case, it is fats. In order for fats to serve as a viable source of energy, they are converted by our bodies into ketones. The process of converting fats into ketones is called ketosis.

By significantly lowering blood sugar and insulin levels, the keto diet has proven to lead to numerous health benefits. The keto diet will help you lose weight, and since the process that underlies the keto diet is natural, it is generally considered a healthy way to lose weight.

What Is Ketosis?

Under ordinary conditions, our body’s cells use glucose as its main source of energy. Glucose is generally derived from common carbohydrates like naturally occurring sugars found in things like fruits, milk, and yogurt. These carbohydrates are also found in starchy foods like bread and past.

The body breaks these carbohydrates down into simple sugars, glucose being the primary sugar that works as an energy source. Glucose can be used and burned up, or metabolized, immediately as an energy source, or glucose can be stored in the liver and muscles in the form of glycogen.

If there is not enough available glucose, or if you have deliberately deprived yourself of glucose as in the keto diet, the body will turn to an alternative source of energy to fuel physiological processes. This alternative energy source is fat stores in the body which are converted into glucose from the triglycerides in fats. The primary by-product of this metabolic process is ketones.

Ketones are acids produced by the liver that ordinarily build-in in the blood and are finally eliminated in urine. When ketones are produced in small amounts this indicates that the body is metabolizing fats to produce energy.

The overall process of breaking down and fat and converting it into glycogens and ketones is called ketosis. This is distinguished from ketoacidosis which is a toxic condition that is not the result of ordinary healthy metabolization of fats for energy production.

Ketosis is a natural process. However, ketosis can cause some unpleasant physical symptoms which, taken together, have given rise to a condition commonly referred to as keto flu.

What Is Keto Flu?

Keto flu is a collection of physical symptoms that some people experience when they first begin the keto diet. Because the keto diet precipitates such a profound change in the way the body accesses and produces energy, it can trigger physical reactions that are generally unpleasant.

These physical reactions can resemble the feeling of having the flu. It is the combination of ketosis and the loss of carbohydrates that produces this “flu.”

The reality is that keto flu is slightly inaccurate and something of a misnomer. Some people develop similar symptoms when they cut back on processed foods or adhere to an anti-inflammatory diet.

But keto flu generally consists of a collection of flu-like symptoms brought on by the keto diet. It is not a serious condition, and, in most cases, it will pass as you become adjusted to the keto diet.

In essence, keto flu is the collection of withdrawal symptoms induced by drastically reducing carbs and the onset of ketosis.

Keto Flu Symptoms

Making the change to a low-carb diet is a major shock to the body. We all need time to adapt to the change and like any major shock to the body, it will produce physical signs of the change.

For some people, the change and period of adjustment can be especially difficult, and the physical reactions may be more pronounced than for others.

The symptoms of keto flu will ordinarily begin with the first few days of being on the keto diet. They will range from mild to severe depending on the person, and last longer for some than for others.

You may experience one or more of these symptoms. Few people will ever go through al of them. Symptoms of keto flu include:


  • Vomiting
  • Constipation
  • Diarrhea
  • Headache
  • Irritability
  • Weakness
  • Muscle cramps
  • Poor concentration
  • Stomach pain
  • Muscle soreness
  • Difficulty sleeping
  • Sugar cravings

Most often people report these symptoms during the first week or two of keeping to the keto diet. Few people report experiencing all of these symptoms, but one or more is enough to cause serious problems. In most cases, the symptoms do subside. This does not diminish how severe and distressing these symptoms can be while you are going through them.

In some cases, the symptoms may persist for more than the first two weeks.

Some people adapt to ketosis better than others. While there are those who will enter the process of ketosis and hardly be aware of it until they see changes in their weight and looks, others will find ketosis to be debilitating.

The symptoms are tied to how the body produces fuel. We ordinarily rely on carbs to get a good supply of glucose. People who are used to eating a lot of carbs, especially refined carbs like pasta, cereals, and soda, are more likely to suffer the ill-effects of ketosis. These people are effectively experiencing withdrawal symptoms from stopping a diet high in refined carbohydrates.

The bottom line is that the reason why some people experience severe keto flu and others have no ill effects may be due to the accidents of genetics. Some people may be genetically predisposed to struggle with the keto diet. Others may have a genetic predisposition to be able to switch over to ketosis with few problems.

Other possible contributing factors to keto flu may include electrolyte loss and dehydration.

Keto flu does not generally last long. Most often keto flu will begin to ease up within about two weeks. As we said above, some people struggle with keto flu more than others and their symptoms may persist longer.

If you find that you are feeling ill for prolonged periods, if you are suffering from things like diarrhea, fever, or vomiting, you should check with your doctor to see if something else is contributing to these problems.

Can You Prevent or Avoid Keto Flu?

Since there are so many things that contribute to developing keto flu, it can be difficult to provide a fool-proof recipe for avoiding the problem. But there are a few precautions you can take that will minimize your likelihood of developing keto flu.

  1. Hydrate: Drinking plenty of water is always a good idea. But the keto diet demands that you stay completely hydrated. Water will help facilitate the biochemistry of ketosis and diminish the physical demands ketosis can place on your metabolism.

Weigh yourself each day to see how much weight you lost. For each pound you lose, add an extra 16-20 ounces of water to your baseline of water intake for the day. You should only do this for the first five days on the ketogenic diet because most of the weight lost during this time will be the result of water loss.

  1. Supplement with Sodium, Potassium, and Magnesium. You lose sodium and potassium during keto because of the decrease in insulin. This can lead to fatigue, headaches, constipation, and cramping.

Eat plenty of leafy greens and add some unrefined salt to your meals. Avocados are a great source of potassium. You can add magnesium with a supplement, and this will help fight fatigue. Magnesium may also help you get better sleep. Pumpkin seeds and almonds are good sources of magnesium.

  1. Get Plenty of Fats. Eat plenty of fats like coconut oil, butter, and cheese. These will easily be transformed in the liver into the alternative fuels you require when moving away from carbs. Other healthy sources of fats that are amenable to keto include ghee, tree nuts like cashews, and cocoa butter.
  2. Low-intensity exercise. Do these low-intensity exercises first thing in the morning. Tale a one-hour walk (put a pinch of salt for sodium in water to take with you). These kinds of exercises early in the day are known to jump-start ketosis. This will help protect against the metabolic strain that can lead to keto flu.
  3. Get Plenty of Sleep. This seems obvious, but it is crucial in the early stages of the keto diet. Getting enough rest, and maybe some extra rest is absolutely necessary as your body adjusts to ketosis. Sleep helps control cortisol levels. Ketosis tends to elevate cortisol levels and it is cortisol that causes some of the symptoms of keto flu.

Aim for 7-9 hours of sleep per night and a 30-minute nap during the day. Avoid caffeine, especially in the first two weeks of being on the keto diet.

Wrapping things up

The keto diet has helped countless people lose weight, get fit, and feel healthy. It has been a resounding success, and the fact that it relies on the body’s natural mechanisms makes keto even more appealing. The problem that has come with the keto diet is the set of symptoms and side effects known collectively as the keto flu.

Fatigue, nausea, headaches, etc. have plagued some people as they attempt to take on the keto diet. These symptoms are not just discouraging, many of them have been debilitating. The good news is that keto flu is most often a temporary condition.

As our bodies adjust to the natural process of ketosis that characterizes the keto diet it goes through a period in which it must reach a new equilibrium. Once we get used to being on the keto diet, the symptoms of keto flu generally go away. Keto flu most often lasts only two weeks at the most.

However, some people experience severe cases of keto flu. More extreme cases of keto flu are often genetically determined. Some people are simply not capable of withstanding the physiological changes that come with the keto diet.

But as we see above, there are some relatively simple things you can do to help prevent keto flu. Pay attention to the signals you get from your body, follow the steps detailed above, and you should move through keto flu with little difficulty.


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