The ketogenic diet is a popular eating pattern that replaces most of your carbs with fat.

Though this diet appears to be effective for weight loss, many people experience uncomfortable side effects when first starting the diet. Headaches are one of the most common symptoms.

If you’re considering keto, you may wonder how best to stave off these headaches.

This article explores the causes of headaches on the keto diet and offers tips for preventing and treating them.

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What causes headaches on keto?

Several factors may cause keto headaches, which typically occur when you’re beginning the diet.

Low blood sugar levels

Glucose, a type of carb, is the main source of fuel for your body and brain.

The keto diet drastically reduces your carb intake, replacing it with fat. This shifts your body into ketosis, a metabolic state in which you burn fat as your primary source of energy (1).

When you start the diet, your body begins relying on ketone bodies instead of glucose, which can cause your blood sugar levels to drop. In turn, this may lead to low blood sugar.

This transition into ketosis may stress your brain, which could result in mental fatigue, or brain fog, as well as headaches (2, 3).

Dehydration

Dehydration is one of the most common side effects of the keto diet. It occurs because people tend to urinate more frequently as they shift into ketosis.

During this transition, your body depletes its stored form of carbs, called glycogen. Given that the glycogen in your body is bound to water molecules, it releases water when it’s used up (4).

Furthermore, your body produces less insulin — a hormone that helps absorb glucose from your blood — on keto because you consume fewer carbs. A drop in insulin levels can affect electrolytes, such as potassium and sodium, which play key roles in hydration.

For example, your kidneys release excess sodium when insulin levels fall, promoting dehydration (5).

Collectively, these factors can contribute to headaches.

Aside from headaches, signs of dehydration include dry mouth, dizziness, and impaired vision (6).

Other potential causes

Several other factors may increase your risk of headaches on the keto diet.

These include the overuse of medications, diuretics, and other drugs that promote dehydration, as well as your age and lifestyle factors like poor sleep, stress, and skipping meals (7).

Low blood sugar levels and dehydration are two significant drivers of keto headaches. Multiple other medicinal and lifestyle factors may likewise increase your headache risk.

How to treat and prevent headaches on keto

Many people experience side effects beyond headaches on the keto diet, including muscle cramps, constipation, fatigue, and dizziness. These symptoms are collectively known as the keto flu (6).

In most instances, dehydration and electrolyte imbalances can worsen these symptoms, making prevention especially important.

Tips to treat or prevent keto headaches

Ensuring proper hydration and eating plenty of nutritious foods can help minimize your risk of dehydration. In turn, this can alleviate headaches — and prevent them from occurring in the first place.

Here are several specific tips:

• Drink plenty of water. As the initial phases of keto involve water loss, it’s important to drink adequate fluids. Aim for at least 68 ounces (2 liters) of water each day.
• Limit your alcohol intake. Alcohol is a diuretic, which means it makes you urinate more often and may increase your risk of dehydration (8).
• Eat more low carb, water-rich foods. Cucumbers, zucchini, lettuce, celery, cabbage, and raw tomatoes have a high water content, which can help you stay hydrated. Some of them are also good sources of electrolytes.
• Eat more electrolyte-rich foods. Keto-friendly foods like avocados, spinach, mushrooms, and tomatoes are high in potassium. Similarly, almonds, kale, pumpkin seeds, and oysters are high in magnesium and suitable for keto (9, 10).
• Salt your food. Consider lightly salting your food to reduce your risk of an electrolyte imbalance.
• Try an electrolyte supplement. Taking an electrolyte supplement may minimize your risk of dehydration and keto flu symptoms.
• Avoid intense exercise. Refrain from intense workouts during the initial days of keto, as they can stress your body and increase your likelihood of headaches.

If you continue to experience headaches after several days or weeks on the keto diet, consult a health professional to ensure that an underlying medical condition isn’t to blame.

Minimizing your risk of dehydration and electrolyte imbalances is key to combatting headaches on the keto diet. Among other steps, you can try drinking plenty of water, eating water-rich foods, limiting alcohol, and salting your foods.

The bottom line

Though the ketogenic diet is a great tool for weight loss, it may cause several side effects when you’re first starting out.

Headaches are one of the most common side effects of this diet, and they’re typically triggered by dehydration or low blood sugar levels.

Nonetheless, you can protect against keto headaches by drinking plenty of water and keeping a close eye on your electrolyte levels, among other tactics.

If your headaches persist beyond a few days or weeks, talk to a healthcare professional.