Written by Dr. Valentina Quintana MD on
May 15, 2022
Reading Time: 6 minutes

Medically Reviewed by our Medical Affairs Team

Written by Dr. Valentina Quintana MD on:

If you’re like most people who are on the keto diet, you’ve probably experienced some brain fog. It’s a common side effect of ketosis and can be frustrating to deal with. Thankfully, there are ways to manage it.

In this blog post, we’ll discuss the causes of ketosis brain fog and offer some tips for dealing with it. We’ll also provide links to other helpful resources about keto flu and brain health.

So, read on for more information about how to keep your mental clarity while on the keto diet!

What exactly is brain fog?

Brain fog or mental fog is a term that describes mental perplexity or forgetfulness. It can be accompanied by fatigue, difficulty concentrating, and memory problems. 

The cause of brain fog is not always clear, but it is often linked to poor sleep, stress, and nutritional deficiencies. It can also be a side effect of some medications and medical conditions.  

The symptoms of brain fog can vary from person to person, but the most common ones include:

  • Feeling tired most of the time
  • Trouble focusing
  • Difficulty with problem-solving 
  • Trouble multitasking
  • Problems with making decisions
  • Changes in mood

Some people experience brain fog as a mild cognitive impairment that lasts for a few days, while others deal with it as a cognitive dysfunction that lingers for months.

What is ketosis?

Ketosis is a metabolic state that occurs when the body starts using fat for energy instead of carbohydrates.

It’s a normal and healthy process that happens when you’re fasting, but it can also be induced by following a ketogenic diet.

The keto diet is a high-fat, low-carb diet that has been shown to offer a number of health benefits. When done correctly, it can help you lose weight, lower your blood sugar levels, and improve your overall health.

Can ketosis cause brain fog?

Yes, ketosis can cause brain fog. This is also known as “keto flu.” The exact mechanism is not clear, but it’s thought to be related to the following factors:

Brain adaptation period

When you start the keto diet, your brain and body have to adjust to using ketones for energy. This process can take a few days to a few weeks, and during this time, you may experience impairment in your cognitive function.

Falling blood glucose

Glucose is the brain’s primary source of energy, and when it’s lacking, the brain may not function as well. This can lead to symptoms like mental fatigue, difficulty concentrating, and memory problems.

Insufficient ketone body production and utilization

If your body isn’t producing enough ketones or if it’s not using them efficiently, you may experience brain fog.

Ketones are produced in the liver and used for energy by the brain. However, if your liver isn’t producing enough ketones or if your brain isn’t using them efficiently, you may experience mental fatigue and other symptoms of cognitive impairment.

Electrolyte imbalance

Another common cause of ketosis brain fog is an electrolyte imbalance. When you’re in ketosis, you may lose water and electrolytes through increased urination. This can lead to dehydration and electrolyte imbalances, which can cause brain fog.

Nutritional deficiencies

Certain nutrients are essential for cognitive function, including omega-3 fatty acids, B vitamins, iron, and magnesium. If you’re not getting enough of these nutrients in your diet, it can lead to brain fog.

Poor hydration status

Dehydration can cause a number of problems, including brain fog. When you’re dehydrated, your body isn’t able to function properly, and this can lead to mental fatigue and other symptoms of cognitive impairment.

Symptoms of Keto Flu

The keto flu is a term used to describe the symptoms that may occur when you start a ketogenic diet. These symptoms are typically mild and resolve within a few days to a week.

The most common symptoms of keto flu include:

  • Fatigue
  • Headache
  • Dizziness
  • Nausea
  • Brain fog
  • Irritability
  • Constipation
  • Increased cravings
  • Difficulty sleeping

How long does the keto flu last?

The keto flu typically lasts for a few days to a week. However, some people may experience symptoms for longer.

People on a keto diet may also experience other side effects, such as:

  • Gastrointestinal issues like constipation and diarrhea
  • Bad breath
  • Muscle cramps
  • Decreased exercise performance 

How to Deal with Ketosis Brain Fog

If you’re experiencing ketosis fog, there are a few things you can do to help ease your symptoms:

1) Start slowly

Starting your ketogenic diet slowly can help your body adjust to the new way of eating and minimize the risk of side effects.

Ease into the diet by gradually reducing your intake of carbohydrates over a period of several weeks. This will give your body time to adjust to using ketones for energy.

You can also try “fat-loading” before starting the diet. This involves eating a high-fat diet for a few days to help your body increase its ketone levels before you start restricting carbohydrates.

If you’re already on the keto diet and experiencing brain fog, try increasing your fat intake and reducing your carbohydrate intake slightly. This may help your body adjust to using ketones for energy and ease your symptoms.

2) Stay hydrated 

Dehydration is a common cause of ketosis brain fog. Make sure you’re drinking enough water throughout the day to stay hydrated.

You can also try adding electrolytes to your diet, such as sodium, potassium, and magnesium. This will help replenish any electrolytes you may be losing through increased urination. 

If you’re still experiencing symptoms, you can try increasing your fluid intake even further. You may need to drink more than the recommended eight glasses of water per day to stay hydrated.

You can also try adding bone broth to your diet. Bone broth is a rich source of electrolytes and other nutrients that can help ease ketosis brain fog.

3) Take an electrolyte supplement

If you’re experiencing ketosis mental fog, an electrolyte supplement may help. Look for a supplement that contains sodium, potassium, and magnesium.

You can also try drinking bone broth or eating foods rich in these nutrients, such as leafy green vegetables, avocados, coconut water, and salmon.

Potassium-rich foods can also help relieve muscle cramps, another common symptom of the keto flu.

4) Consume more fat

If you’re on the keto diet, make sure you’re getting enough fat. Fat is an essential nutrient and helps your body burn ketones for energy.

Increase your fat intake by adding more olive oil, coconut oil, butter, avocado, and fatty fish to your diet. You can also try using MCT oil, which is a type of coconut oil that’s easily absorbed and used for energy.

If you’re still experiencing ketosis fog, try increasing your fat intake even further. You may need to consume up to 70-80% of your calories from fat to help your body adjust to using ketones for energy.

5) Get plenty of rest

If you’re experiencing ketosis mental fog, make sure you’re getting enough sleep. Sleep is essential for overall health and can help your body recover from the stress of starting a ketogenic diet.

Aim for seven to eight hours of sleep per night. If you have trouble sleeping, try limiting your caffeine intake and avoiding screen time in the hours leading up to bedtime.

You can also try taking a magnesium supplement, which can help relax your muscles and improve sleep quality.

If you’re still experiencing symptoms after trying these tips, talk to your doctor or a registered dietitian. They may be able to recommend other treatments or lifestyle changes that can help ease your symptoms and increase your mental clarity.

What are the cognitive effects of ketosis?

Brain fog is one of the most common cognitive effects of ketosis. Other effects include:

  • Difficulty concentrating
  • Trouble remembering things 
  • Problems in making decisions
  • Challenges in problem-solving
  • Increased irritability
  • Mood swings 

These effects are usually temporary and resolve within a few days or weeks as your body adjusts to using ketones for energy. However, if you’re experiencing severe or persistent symptoms, talk to your doctor.

How Ketosis Works in the Brain

Ketosis is a metabolic state in which your body burns ketones for energy instead of glucose. When you restrict carbohydrates, your body doesn’t have enough glucose to burn for energy.

Your liver starts converting fat into ketones, which can be used for energy. This process is known as ketogenesis.

As your body adjusts to using ketones for energy, you may experience a number of cognitive effects, such as brain fog. These effects are usually temporary and resolve within a few days or weeks.

The Benefits of Ketosis on Brain Health

In addition to the cognitive effects of ketosis, there are also some potential benefits.

Some research suggests that ketosis may help improve brain function in people with Alzheimer’s disease and other forms of dementia.

Ketosis may also help protect the brain from damage after a stroke.

However, more research is still needed to understand the potential benefits of ketosis on brain health.

If you’re interested in trying a very low-carb diet, talk to your doctor first. They can help you create a plan that’s right for you and manage any potential risks.

The Bottom Line

Ketosis brain fog is a common side effect of the ketogenic diet. However, it’s usually temporary and resolves within a few days or weeks.  There are also some potential benefits of ketosis on brain function.

If you want to learn more about brain fog and how to clear it naturally, here are more resources on the topic. Also, check out this online community of brain health advocates. 

Join The Mental Health Community You've Been Dreaming Of


This discord family is a safe place where we can all (anonymously if we choose) talk about and seek help for what is going on in our heads.

{"email":"Email address invalid","url":"Website address invalid","required":"Required field missing"}
Insert About the Author
>