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Keto Headache: Why You Have It and How to Prevent It


One of the most common side effects of transitioning into a low-carb, ketogenic diet is the dreaded keto headache (also called a low-carb headache). But don’t let the flu-like side effects in the first week or two discourage you from your ketogenic journey.

There are specific lifestyle hacks and nutrient protocols you can take to prevent headaches induced by suddenly reducing your carbohydrate intake.

Eventually, your body will adapt to using fats as energy and the symptoms will disappear.

Read on to explore the reasons you might experience a keto headache and the steps you can take to prevent it as you reap the powerful health benefits of ketosis.

What Happens to Your Body When You First Go Keto

You’ve probably spent a good portion of your life feeding your body large amounts of carbohydrates, many of them from processed food sources.

This means your cells, hormones, and brain have adapted to using carbohydrates as their main source of energy.

Transitioning to a fat-dominant fuel source will confuse your body’s metabolism in the beginning.

This metabolic confusion will put your body through an “induction phase.”

This is the time when your metabolism works overtime to get accustomed to using ketones for energy (from fats) rather than glucose (from carbohydrates).

During this phase, you may experience flu-like symptoms commonly referred to as the “keto flu” — especially headaches and brain fog — because your body is going through physical carb withdrawal.

Mental Fog Is Normal at the Start of Keto

One of the very first signs of this “induction phase” comes from your brain losing its main source of fuel — glucose.

If you’ve never followed a low-carb, high-fat diet, your brain has been using carbohydrates as its main energy source.

When you start increasing your fats and restricting carbs, your body starts to burn through its last stores of glycogen. At first, your brain won’t know where to find the energy it needs because of the lack of carbohydrates.

It’s normal to start staring off into space, experiencing headaches, and feeling irritable.

A good way to combat these symptoms is to go as low-carb as possible when you’re first starting out. This way your body is forced to use up all of its glycogen stores much faster.

Many people try to taper off their high carb intake over time, but doing so will only make the brain fog last longer.

When you get into a state of ketosis, a large portion of the brain begins to burn ketones instead of glucose. It can take a few days or up to a couple of weeks for the transition to happen.

Luckily, ketones are a highly potent fuel source for the brain. Once your brain gets accustomed to using fats as energy, brain function is optimized.

Many studies have shown long-term ketogenic dieters to have improved brain cognition. The keto diet has even been considered for treating brain conditions such as memory loss[*][*][*].

The Keto Induction Phase Is Stressful on Your Body

Without much sugar from carbohydrates present, your body will begin to decrease blood sugar levels and increase the production of the stress hormone, cortisol.

Cortisol is a glucocorticoid hormone released by your adrenals to make sure your energy level is sufficient to survive. When you have low blood sugar levels, your brain sends a signal to your adrenals to release cortisol. Your body will begin to burn glycogen (stored glucose) for fuel.

Carbohydrate restriction — and thus, the keto diet — may sound like a bad idea due to your increased body stress triggering the release of additional cortisol. But this isn’t the case. Over time, your body will adapt and develop a preference for using fat as fuel through ketosis.

One study tested three separate diets: a low-carb diet, a low-fat diet, and a low-glycemic diet. This study showed that the different diets had significantly different metabolic effects, with the low-carbohydrate diet proving to be the most effective[*].

Causes of Keto Headache

One of the most common symptoms when making sweeping dietary changes, like the keto diet, is the pounding headache that accompanies carbohydrate restriction.

When your body’s been running on high-carb foods like bread and starchy vegetables your whole life, making a large transition to burning fat as fuel will require an adjustment period.

Keto headache is just one keto flu symptom and shouldn’t be compared to the normal flu. The keto flu isn’t viral or contagious and you’re not sick — you’re adapting.

What Causes a Keto Headache?

There are three main reasons why you may develop a headache after going low-carb: dehydration, electrolyte imbalances, and carbohydrate or sugar withdrawal.

The typical Western diet contains large amounts of sugar which give your body an instant rush.

Sugar impacts your brain through the same reward system that is seen with equally addictive substances, like cocaine, which is why you experience symptoms similar to drug withdrawals[*].

In fact, it’s the “sugar high” that’s responsible for your increased sugar cravings. The more sugar you eat, the more you want.

How Long Does the Keto Headache Last?

Some people may not experience any withdrawal symptoms at all. Everyone is different and the length of the symptoms depends on several factors.

For example, if you followed a diet relatively low in carbs before going keto and ate large amounts of green vegetables (or took a high-quality greens supplement), there’s a chance that your symptoms would be very short-lived or even nonexistent.

On average, the keto headache will last anywhere from 24 hours to one week.

In rare cases, it can take up to 15 days for the symptoms to subside.

Some people prefer to start keto on the weekend so the symptoms are more tolerable and won’t affect everyday life too much.

Dehydration Is Common During the Keto Induction Phase

When you adopt a low-carb high-fat ketogenic lifestyle, your body begins to excrete excess water.

Don’t get too excited when you notice a lot of weight loss after first beginning keto. The bodyweight reduction isn’t all from fat loss; it’s water being flushed out of your body.

Ketosis is known for its strong diuretic effect. This means your body is excreting both water and electrolytes which leads to reduced water retention[*].

Water is stored in your body from carbohydrates. When you restrict carbohydrates, your body begins to excrete water rapidly.

For each gram of glycogen (from carbs) used as energy, twice the mass is lost in water.

Once your body enters ketosis, your body starts sparing glucose but water loss continues. Having ketones present in your body will lead to more water excretion.

It’s vital to drink plenty of water while adapting to carbohydrate restriction in order to mitigate dehydration symptoms and maintain your overall health and well-being.

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Electrolyte Imbalances Are Common When You First Go Keto

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

When your body excretes water, you begin to flush out these essential electrolytes which are crucial for several different bodily functions like energy production, body temperature control, and optimal brain function.

Your daily electrolyte requirements are higher on keto compared to a normal diet.

An electrolyte supplement can help while you’re in transition.

Sodium Requirements

Insulin plays a huge role in electrolyte maintenance. It’s a hormone that lowers your blood sugar when it’s too high[*].

The main job of insulin is to shuttle sugar into cells so they can use it as fuel and deposit excess sugar into fat. It also works to promote sodium absorption in the kidneys[*].

When you start a low-carbohydrate diet, insulin levels are much lower.

The sodium eventually draws more fluid into your kidneys to prepare for the excretion of water.

Less insulin in the body means there is less sodium present.

Low sodium levels in your body are one of the main reasons why you may experience decreased energy levels and headaches while on a low-carb diet.

You should aim for 5,000 to 7,000 mg of sodium throughout the day.

This can be consumed in the form of pink Himalayan sea salt, bouillon, bone broth, and even sodium pills.

Potassium Requirements

If you are potassium-deficient, you can expect to experience depression, irritability, constipation, skin problems, muscle cramps, and heart palpitations[*]

To combat this you should consume ~3,000 mg of potassium a day.

Here is a list of keto-friendly foods that contain ample amounts of potassium:

  • Nuts: ~100-300 mg per one oz serving
  • Avocados: ~1,000 mg per serving
  • Salmon: ~800 mg per serving
  • Mushrooms:  ~100-200 mg per serving

It’s important to note that too much potassium can be dangerous. While it would be difficult to reach the upper threshold of toxic levels, it’s best to steer away from potassium supplements and stick to the natural sources listed above.

Magnesium Requirements

While magnesium deficiency is not as common for low-carb dieters, it’s important to maintain optimal levels.

A magnesium deficiency can lead to muscle cramps, dizziness, and keto headache[*].

The recommended daily average for people on the keto diet is ~400 mg of magnesium a day.

Try these keto-approved, magnesium-rich foods:

  • Cooked spinach: ~75 mg per cup
  • Cacao powder with dark chocolate: ~80 mg per one tbsp of cacao powder
  • Almonds: ~75 mg per 1 oz
  • Salmon: ~60 mg per fillet

How to Prevent a Keto Headache

The headache you get when adapting to burning fat for fuel comes from an impaired ability to effectively use fat as energy.

Any time your body’s ability to burn fat is impaired, you have a hard time losing weight. You become very hungry when your blood sugar runs out — no matter how much fat you have available to burn.

To combat the keto headache, you must improve your body’s metabolic flexibility to burn fat as energy instead of glucose.

Metabolic flexibility is your capacity to adapt fuel oxidation to fuel availability. This is your body’s ability to switch from one fuel source to another (from carbohydrates to fat).

Your keto headache symptoms will soon diminish once you become used to using fat (ketones) as energy.

Here are five techniques you can implement today to prevent keto headache:

#1. Drink Water and Salt

When you start eating a low-carb diet, your insulin levels will naturally go down. You won’t hold onto as much sodium as compared to a traditional Western diet with a moderate amount of carbs.

You also begin to excrete stored water when you restrict carbohydrates.

Sodium deficiency is one of the main causes of keto headache and can be mitigated by adding more water and salt into your system.

It’s important to increase the amount of salt you consume because drinking more water will flush out sodium at the same time.

Consuming bouillon or bone broth will help you maintain proper amounts of sodium.

If you are still having difficulty increasing your salt intake on a low-carb diet, supplementing with sodium supplements and simply adding more salt to every meal will help.

#2. Eat More Fats

Eating more dietary fat will help your body get accustomed to using fats as energy. Since you’re replacing carbs with fats as your main source of calories, you need to consume larger amounts of fat than you were previously.

You should aim for 65-70% of your total calories from fats.

Taking the time to track your fat intake should be a priority in the beginning since it’s very easy to undereat fats. This is because fats are more calorically dense and will fill you up quicker.

Eat fatty meats like rib-eye steak, bacon, salmon and chicken thighs. Add coconut oil and butter to each meal to increase your fat intake.

#3. Take Supplements

Supplements can greatly help your conversion into a fat-fueled machine, but it’s important to never use supplements as a replacement for dietary deficiencies.

Some key vitamins and minerals that can help mitigate a keto headache include:

  • L-carnitine: High fat intake from the keto diet means more fatty acids need to be moved into the mitochondria for fat oxidation. Carnitine is required for effective transportation.
  • Co-Enzyme Q10: This is an antioxidant responsible for the cellular process of creating energy. It’s another supplement that helps mobilize fat and will help you transition into ketosis faster.
  • Omega-3 fatty acids: Fish oil is a potent natural anti-inflammatory. Consuming omega-3’s will also help to lower triglyceride levels in your body which are fat molecules held in the blood for later use.

#4. Exercise More

Studies have shown that exercise can improve your body’s metabolic flexibility.

Exercising increases both fat utilization and improves weight loss, both are contributing factors to combating the dreaded keto headache[*].

One study shows that the benefits of exercise go beyond weight loss. It also helps to repair broken metabolisms. This study showed that after exercise, the metabolism of people with type 2 diabetes was restored and they were able to utilize calories for energy more efficiently[*].

Making a habit to work out will help you regain your metabolic flexibility and stimulates your body to increase fat burning both during exercise and at rest.

Exercise will greatly improve the speed at which your body starts using fat as its main source of energy and will help mitigate symptoms of keto headache.

#5. Supplement With Exogenous Ketones

Taking exogenous ketones is an effective way to elevate your ketone levels, even if you haven’t fully converted to using fats as a primary source of energy. They can elevate your beta-hydroxybutyrate (BHB) levels by up to 2 mMol after consumption.

Exogenous ketones cause blood glucose to decrease due to an increase in insulin sensitivity. This is important during the induction phase because you’re priming your body to start preferring fats as energy rather than carbohydrates.

They also contain ample amounts of calcium, magnesium, and sodium which are critical electrolytes your body needs for peak brain and body functioning.

By adding exogenous ketones into your routine, you will drastically mitigate the severity of your keto-induced headaches.

Don’t Be Discouraged by the Keto Headache

While the keto headache may sound daunting and may discourage you from adopting a keto diet, taking the steps to mitigate the symptoms isn’t as hard as some make it out to be.

Replacing essential nutrients and minerals, exercising frequently, and maintaining a proper low-carb, high-fat diet will ensure that your keto flu-like symptoms diminish sooner than later.

Remember that a low-carb headache is a normal induction stage of the process and happens to most people who adopt this way of eating.

The light at the end of the tunnel is much closer than you think. Let this encourage you to stick it out until you begin to experience the benefits of a low-carb, high-fat ketogenic lifestyle. It will all be worth it!


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