What Is The Keto Headache and How To Prevent It?

  • Post last modified:August 11, 2021
  • Reading time:13 mins read
  • Post comments:0 Comments

In recent years, more and more people have begun to use the ketogenic diet for weight loss. Although its effect is obvious, many people experience various kinds of discomfort when they first start a keto diet. Commonly known as “keto flu“, experiencing a headache is one of the most common symptoms.

When you transition from a normal high-carb diet to a very low-carb diet (ketogenic diet), your body will change from using glucose as an energy source to using fat (ketone bodies) as a source. 

In order to adapt to this process, your body must make some adjustments.  With these adjustments, you may experience some discomfort, such as headache, brain fog, bad breath, insomnia or constipation.

However, these symptoms are temporary. They usually will disappear when your body is fully adapted to the new diet. Then, you can truly benefit from a ketogenic diet.

In this article, we are going to talk in detail about why the keto diet causes headaches and how to prevent it.

What Is The Keto Headache

What Happens To Your Body When You Start A Keto Diet?

The high-carbohydrate low-fat diet formulated and promoted by the Nutrition Society for 40 to 50 years, has long been popular with many people.

When you consume a lot of carbs for a long time, your organs, tissues, cells and brain will habitually use glucose (from carbs) as its main energy source.

When starting a keto diet your body can’t get enough carbohydrates, so it can disturb your metabolism.

This metabolic disorder affects your body during the “induction period”, which is the adaptation period.

At this stage, you may experience the “keto flu”. The symptoms and severity are different for everyone, but headaches, brain fog or insomnia are the most common. 

This is because your brain suddenly loses its main fuel – glucose.

When your brain doesn’t get enough fuel for the energy you require, you may experience a headache and some irritability.

This process can last from a few days to a few weeks. It usually lingers until your body has completely entered a state of ketosis when your brain begins to adapt to using ketone bodies as fuel.

If you want to shorten the period of keto discomfort and speed up the fat-burning, you must find a way to enter ketosis as soon as possible.

What Are The Causes Of Keto Headache? 

Headache caused by a ketogenic diet is a dull painful feeling. In severe cases, blurred vision and even migraines may occur.

The main reasons for these symptoms are as follows:

1. Low Blood-Sugar

When you start a ketogenic diet, your carbohydrate intake will be greatly reduced. This results in a drop in blood sugar levels.

Since your body has not yet fully adapted to this new form of hypoglycemia, it will temporarily increase stress on your brain and nervous system.

Studies have shown that glucose imbalance may cause brain blood vessels to constrict, thereby reducing the brain’s oxygen supply, causing discomfort. Once the glucose level is stabilized by nutritional ketosis, your headache will subside.

In the case of hypoglycemia, the circulating blood sugar is too low to meet the body’s energy needs. The result is a change in hormone levels (epinephrine and norepinephrine) which in turn causes changes in the brain (vasoconstriction), resulting in your body experiencing headache and fatigue.

2. Dehydration

You may have noticed that you lost weight rapidly in the first few days of a keto diet. I have experienced this myself. I lost 6 pounds in the first week. This is actually caused by the loss of water.

When you are in the transitional phase of ketones and use up the glucose (glycogen) stored in your body, your body will excrete excess water.

This is because every gram of glycogen stored is released with three grams of water [*]. In other words, for every gram of glycogen (from carbohydrates) used as energy, three times as much water is lost.

Therefore, when your body consumes all its glucose reserves, it also eliminates a lot of water at the same time.

If you don’t drink enough water, you can get dehydrated, along with possibly experiencing a headache caused by dehydration.

3. Electrolyte imbalance

The main electrolytes to keep a close eye on are magnesium, sodium and potassium.

When you reduce the intake of carbohydrates, your body produces less insulin.

Since insulin’s job is to control the glucose in the blood, when you stop supplying carbohydrates to the body, the blood sugar concentration will decrease. Therefore there is no need to secrete much insulin.

As insulin decreases, your kidneys excrete more sodium, which is an electrolyte that regulates hydration. As sodium is excreted, the body may also lose other essential electrolytes, such as potassium and magnesium.

This electrolyte imbalance is one of the main causes of keto flu including headache.


What Is A Keto Headache

How Long Does The Keto Headache Last?

The headache caused by the keto diet is temporary. The duration depends on a person’s makeup and circumstances.

Some people may have almost no symptoms, while others may have a headache for several days. The average is about 2 to 5 days, with the longest duration lasting as long as two weeks.

Generally speaking, the severity of headaches depends on your previous eating habits.

If you have been on a high-carb diet, the symptoms of keto flu, including headaches, will be more severe.

In the same way, if you normally eat a lower-carb diet, it may be easier to go on a ketogenic diet. In this case, the corresponding discomforts can be less or not at all.

How to Prevent A Keto Headache

In the early stages of a ketogenic diet, physical discomfort is difficult to avoid, especially headaches.

However,  you can still try some methods to relieve your symptoms.

1. Drink plenty of water:

Your body will lose water in the early stage of ketosis, so hydration is the first priority to prevent and stop a keto headache.

Drink at least 2 liters of water or eat more water-rich vegetables, such as lettuce.

2. Replenish electrolytes:

As mentioned above, electrolyte imbalance is one of the main causes of keto flu. Therefore, eating more electrolyte-rich foods, such as bone soup and green leafy vegetables can help alleviate this imbalance.

Even adding a pinch of Himalayan salt to a glass of drinking water can effectively relieve any ketogenic discomfort, including headaches and brain fog. 

3. Gradually reduce carbohydrates intake:

If you have been eating a high-carb diet, when you change to a keto diet, it is recommended to slowly reduce your carbohydrate intake.

This will give your body more time to adapt to the new diet. It can also reduce any ketogenic discomfort.

4. Avoid strenuous exercise:

In the initial stage of ketosis, your body is under a lot of stress while transitioning to a new metabolic method.

If you perform vigorous exercise during this period, it may increase the pressure on your body and brain,  causing more severe headaches.

5. Ensure adequate quality sleep:

The fact is, insomnia is also one of the causes of ketogenic discomfort because poor sleep can aggravate headaches. 

Therefore, try to ensure a regular sleep schedule. Additionally, it is wise to create a comfortable sleeping environment.

Finally, if it is safe for you, you can also take melatonin to help you sleep.



Headache is a common adverse reaction of the ketogenic diet. This symptom mainly occurs in the early stage of the keto diet.

When your body has not fully adapted to this new diet, your brain may experience temporary headaches, brain fog or irritability. This is due to a lack of glucose as an energy source.

The best ways to stop or prevent keto headaches are by supplementing water intake, eating more foods rich in electrolytes, ensuring quality sleep and avoiding strenuous exercise. If you continue to adhere to the keto diet, the keto flu will usually pass. 

Leave a Reply