Keto Headaches: Why They Happen and How to Prevent Them

A keto diet, also known as a ketogenic diet, is a very low carb, high-fat diet. It is designed to force your body into using fat instead of glucose (sugar) for energy.

The keto diet started out as a way to control seizures in certain people with epilepsy. However, in recent years, keto has been gaining attention for its ability to promote weight loss.

Since a keto diet involves drastically cutting carbs, there will be some initial side effects when starting this diet. One side effect many people experience is headaches.

This article will discuss how to handle the adjustment period and prevent keto headaches as you transition to a very low-carb diet.

Keto Headache

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What Happens in Your Body When You Go Keto

On a ketogenic diet, you restrict your carbohydrate intake to 5% to 10% of your daily calories. You'll consume about 70% to 80% of your daily calories from fat and around 10% to 20% from protein.

The main goal of the keto diet is to send your body into ketosis. Ketosis happens when your body switches to burning fat because there aren't enough carbs to burn for energy. When your body breaks down fat, it produces ketones. This is where the name "keto" diet originated from.

As your body transitions to burning fat, you may experience unpleasant side effects. The term "keto flu" is commonly used to describe the side effects experienced when beginning the diet.

Signs and Symptoms of Keto Flu

When you transition to a low-carb diet, it takes time for your body to adapt. For some, signs of the keto flu may start appearing within just a few days of cutting your carb intake. Symptoms typically peak within the first week and gradually fade by week four of the diet.

The severity of the symptoms can range from mild to severe, depending on the person.

The most common symptoms of the keto flu include:

  • Headache
  • Brain fog
  • Stomach pain/discomfort
  • Nausea
  • Flu-like symptoms
  • Fatigue
  • Dizziness
  • Sore throat
  • Body aches
  • Feeling faint
  • Heartbeat alterations

Causes of Keto Headaches

There are several potential causes of headaches during the first few weeks of starting the keto diet.

Low Blood Sugar

On a high-carb diet, your brain is powered by glucose, a type of carbohydrate. When you begin a keto diet, your body begins to burn stored fat for energy instead of glucose.

As your body shifts into ketosis, it could cause your blood sugar levels to drop. This is known as hypoglycemia.

Hypoglycemia can cause a dull, throbbing headache in the temples.


As our body begins to shift into a state of ketosis, we begin to urinate more frequently, which can lead to dehydration.

During the transition, your body uses up stored glycogen for fuel. Glycogen found in your body is bound to water, thus releasing excess water as glycogen stores are used up.

This is why many people notice quite a lot of weight loss during the first several days of starting a very low carbohydrate diet.

If you aren't drinking enough fluid while you are following the keto diet, it can lead to dehydration and headaches.

Electrolyte Imbalance

When you restrict carbohydrates, your body naturally produces less insulin. A drop in insulin causes your kidneys to excrete more sodium.

Dehydration can lead to sodium, magnesium, and potassium imbalances as well.

In addition to a headache, low sodium levels in the body can lead to nausea, vomiting, fatigue, and cognitive impairment.

Treating and Preventing Keto Headaches

Fortunately, there are ways to treat and even prevent headaches when starting keto. It's essential to stay hydrated and eat a nutrient-rich diet to minimize your risk of dehydration and headaches.

Drink Plenty of Water

When you first begin the keto diet, your body will lose excess water weight, making it important to stay hydrated.

Although there is no recommendation for the exact amount of water you need on keto, most experts agree that we should drink at least 8 to 10 cups of water on a standard diet.

Get More Sodium, Potassium, and Magnesium

When levels of key electrolytes like sodium, potassium, and magnesium are low, it's important to replenish them. Water is essential to stay hydrated, but you'll need to replenish your electrolytes through the foods you eat or an electrolyte supplement.

Potassium-rich foods include:

  • Avocados
  • Mushrooms
  • Pumpkin seeds

Good dietary sources of magnesium are:

  • Cashews
  • Peanut butter
  • Dark chocolate
  • Leafy greens

You can add more salt to your foods to increase your daily sodium intake or add a pinch of salt to your water.

Avoid Intense Workouts

On a normal diet, your body uses glucose and glycogen stored in the muscle for a quick burst of energy. As glycogen stores become depleted, you may not have enough glycogen to fuel your workout.

Research shows that ketogenic diets can inhibit performance by up to 20% during the initial phases of the diet. However, after your body adapts to the ketogenic state, performance can actually improve.

Until your body adapts, you may want to avoid intense workouts because it can lead to more stress on your body and may cause headaches. You may also sweat out extra water which can worsen dehydration.

Plan Low Carb, Nutrient Dense Meals

In order to maintain optimal health on a keto diet, consider planning your meals in advance. This can help you stay on track and properly fuel your body to minimize unpleasant side effects when you begin keto.

Eating enough fat can be scary as many of us have been told to limit or avoid fat at some point in our life. However, to effectively transition into ketosis and have enough energy, you must consume at least 70% to 80% of your total daily calories from fat.

This can also help maintain healthy blood sugar levels and minimize headaches. Avoid processed and refined foods and eat more whole, natural foods to help you feel your best.


In order to effectively use the keto diet as a weight-loss tool, it's important to adhere to the diet's macronutrient guidelines. Even if you follow an appropriate keto diet, you may experience unpleasant side effects during the first few weeks. Headaches are one of the most common side effects of this diet. Electrolyte imbalances and dehydration typically cause them.

To treat or prevent headaches commonly experienced in the beginning phases of the keto diet, it's important to:

  • Stay hydrated
  • Eat nutrient-rich foods
  • Avoid very intense workouts

As always, have a conversation with your healthcare provider before making any changes to your diet.

A Word From Verywell

Sticking to a keto diet can be challenging. This is especially true if you experience negative symptoms within the first few weeks of starting keto.

It's important to give yourself grace and nourish your body to help you feel your best and minimize unwanted symptoms when starting the keto diet.

Consider visiting with a registered dietitian who has experience with the keto diet to help you stick with it for the long run.

Frequently Asked Questions

  • What are the symptoms of carbohydrate withdrawal?

    Symptoms of carbohydrate withdrawal or the beginning of starting the keto diet are bloating, diarrhea, gas, headache, weakness, muscle cramps, and fatigue.

  • Can a low carb diet give you a headache?

    Yes, headaches are common side effects of low-carb diets like the keto diet and are often caused by electrolyte imbalances, dehydration, or low blood sugar.

  • How long does the keto headache last?

    Keto headaches can last anywhere from a few days or a few weeks and can vary by individual.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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