Intermittent Fasting Headache: Here's How To Cure It

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Intermittent fasting is praised as a tool to lose weight, lower cholesterol, improve sleep, increase focus and productivity. We could go on and on about the various intermittent fasting benefits both science and fasting fans have reported. 

However, let’s not forget about the possible negative consequences of restricting your eating hours. While the most obvious side effect would be hunger, there are a few other troubles you might be experiencing. This time we will be looking more into a common side effect – intermittent fasting headache.

Here are the two main questions to answer in order to make your intermittent fasting experience headache-free:

What Causes an Intermittent Fasting Headache

In the International Classification of Headache Disorders, fasting headache is classified as headache attributed to disorder of homeostasis. 

It means that these headaches are associated with metabolic or systemic disruptions and diseases. While fasting can be one of the causes, you will possibly feel similar symptoms when suffering from a headache caused by high altitude, diving, or sleep apnea.

How does a headache while fasting feel? It is likely to be diffused or located in the frontal region, and the pain is non-pulsating and of mild or moderate intensity. However, depending on the headache cause and many other factors, it might feel differently.

The likelihood of developing a fasting headache increases directly depending on the duration of the fast. In most cases, the headache occurs after around 16 hours of fasting and resolves within 72 hours after resuming food intake. Therefore, people doing prolonged fasting, are more likely to experience a headache.

Any other factors that can increase the probability of suffering from a headache during fasting? While much remains to be understood about this, studies show that headache sufferers have a higher risk of developing a headache during fasting than people who do not usually suffer from headaches.

While the precise cause of fasting headache is still being discussed, there are a few factors that could be responsible for this annoying fasting side effect. Dehydration, caffeine withdrawal and hypoglycemia, or in other words, a fall in blood sugar to levels below normal, could be the three most common fasting headache causes.

Still, it’s important to also pay attention to lesser-known headache triggers like stress, fatigue and lack of sleep during the fast. Especially at the beginning of your intermittent fasting journey, your body is undergoing drastic lifestyle changes that can cause emotional and physical discomfort. 

Now when we have identified some of the possible fasting headache causes, let’s get to the most important part – figuring out how to cure it and have pain-free fasting hours.

How To Cure an Intermittent Fasting Headache

As a doctor would say, “treatment depends on the cause”. The issue is that you might not always be aware of what exactly has triggered your fasting headache. Therefore, we have listed below multiple possible triggers and ways to avoid or treat the headache caused.

The good news is that these fasting headache cures can not only help get rid of the pain but also set you up for a more enjoyable fasting experience.

dehydration headache while fasting

Fasting headache caused by dehydration

Cure: Stay hydrated

We’ve all heard that 60% of our body is made up of water. That obviously makes it really important to consume enough of it.

The human brain consists mostly of water, and it is very sensitive to the amount of water available to it. When the brain detects that the water supply is too low, it begins to produce histamines. They directly cause pain and fatigue, in other words, a headache and low energy that usually accompanies it. 

Staying hydrated is particularly important when doing fasting, as you are not intaking water from food. Around 20-30 % of our water intake actually comes from food, which means you should compensate that with drinking more fluids.

And not just any fluids. Plain tea, black coffee and water are the 3 intermittent fasting safe drinks. However, while contrary to popular belief, coffee and tea can actually contribute to the daily fluid intake, water is still your best bet. 

Try sticking to at least the recommended eight 8-ounce glasses, which equals about 2 liters, or half a gallon a day. Adding a slice of lemon, cucumber or opting for sparkling water can add a little kick to your water.

Oh, and let’s not forget that a glass of water, coffee or tea can help fight off hunger for just a little longer.

fasting headache

Fasting headache caused by hypoglycemia

Cure: Adjust your fasting diet

Fluctuation in blood sugar is a common cause of headaches. This type of headache would usually be triggered when a fast rise follows a rapid drop in blood sugar levels.

This happens when your last meal before the fast is high in simple sugars and carbs, such as rice, bread, fruits and sugar. This so-called sugar headache would start to appear around four hours after eating – when the high blood sugar levels have dropped. 

To avoid this type of headache, try reducing carbs in your last eating window meal. Emphasize healthy fats like fatty fish, seeds, avocado, olive oil, and eggs or protein-rich foods such as lean chicken, pork or beef, tofu, beans and lentils. You can even try keto diet or keto-inspired dishes.

caffeine withdrawal fasting headache

Fasting headache caused by caffeine withdrawal

Cure: Reduce caffeine intake slowly

Caffeine withdrawal will be the main headache cause if you’ve decided to practice a more strict fasting form which only allows pure water (or dry fasting with no water at all).

Most avoid coffee drinkers will experience a headache when their daily caffeine level is not met. Therefore, to avoid this unpleasant side effect, the best option is to slowly reduce your caffeine intake to let the body adapt. That means reducing caffeine content and switching to decaf coffee or simply reducing the number of your daily coffee cups.

stress intermittent fasting headache

Not sure about the headache cause?

Cure: Rest and relax

Exact headache causes are often still a mystery to doctors and scientists. Therefore, it’s quite likely you won’t be able to find an exact trigger that has caused your fasting headache.


Fatigue, stress, lack of sleep and overexercising can be among the many reasons you’re feeling unwell both while fasting and following a regular eating pattern. Get on a healthy sleep schedule, try meditation or yoga or just find what works the best for you to relax and switch off.

Often a headache while fasting will go away on its own. However, make sure to listen to your body; if the pain gets unbearable return to your normal eating pattern and consult with a doctor.

HOW TO MASTER YOUR INTERMITTENT FASTING LIFESTYLE

Whether you’re an intermittent fasting beginner or already practicing for a while, there’s always room for improvement.

In 21-days you can learn proven tips on overcoming all the challenges to successfully make intermittent fasting a solid habit. We have created a 21-day Intermittent Fasting Challenge keeping both beginners and experienced fasting fans in mind. Oh, and a delicious intermittent fasting meal plan is included! 

We start the challenge every Monday. Join us today!

RESEARCH and TEXT BY:

TAURAS SINKUS

TAURAS SINKUS

Tauras is the founder and face of the 21 Day Hero. While being obsessed with mind and productivity hacks, he is hooked up with HIIT type group training and cooking gourmet meals almost every day. Tauras is widely known in the startup community for his kick-ass social media and marketing skills too!

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