How Fasting Can Cause a Headache

A Closer Look at a Fasting Headache

How Not Eating May Cause a Headache. Peter Dazeley/Getty Images

With the busy lives so many of us lead, it's unfortunate — but not surprising — that eating can sometimes get put on the back burner. And fasting can lead to a headache that can further damper your already stressful day.

Let's take a closer look at fasting headaches and how you can prevent them.


Individuals who fast for more than 16 hours may develop a fasting headache. According to the thrdedition of the International Classification of Headache Disorders (2013), the headache occurs during the fasting period and resolves within 72 hours of food intake.

Also, symptoms of a fasting headache must include at least one of the following headache characteristics:

• Frontal location (forehead)

• Diffuse pain

• Non-pulsating quality

• Mild or moderate intensity

Interestingly, the likelihood of a fasting headache developing increases with the duration of the fast. Also, Tortellini et al in his study in Headache also notes that headache sufferers are more likely to develop a headache during fasting than individuals who do not typically suffer from headaches.


The cause of fasting headaches is still controversial. One potential mechanism is hypoglycemia or low blood sugar. Tortellini et al in Headache suggests that in genetically predisposed individuals, small changes in blood glucose may alter pain receptors in the brain, leading to a fasting headache. Hypoglycemia may also induce vasodilation, leading to migraine attacks—this is different through from a fasting headache, which is not like a migraine (i.e., non-pulsating, often bilateral).

Here is why many scientists do NOT think hypoglycemia is the cause of fasting headaches:

  • In healthy individuals, glycogen levels in liver are enough to sustain normal glucose levels for 24 hours.
  • Fasting headache can occur in the presence of normal glucose levels.
  • Insulin-induced hypoglycemia does not produce headache in migraineurs.
  • Headache is not a symptom of hypoglycemia that urges patients to seek ED care.
  • Hypoglycemia-induced headaches have a pulsating quality, while fasting headaches do not.

Caffeine withdrawal has also been linked to fasting headaches—but is also controversial, like hypoglycemia. A caffeine-withdrawal headache generally occurs about 18 hours after the last caffeine intake—similar to that of a fasting headache. A caffeine-withdrawal headache also has features similar to a tension-type headache, like a fasting headache. Again though, like hypoglycemia, people still get fasting headaches even when they do not consume caffeine. This disputes caffeine withdrawal as a primary cause of fasting headaches.

Many scientists think that like hypoglycemia-induced headaches, a caffeine withdrawal headache is a separate entity from a fasting headache. This is supported by the IHS, which codes these headaches separately.

Other potential causes of fasting headaches are dehydration and the stress that led to the fasting state.

Overall, the precise cause of fasting headaches is difficult to tease apart. There may just be a number of causes and/or it varies for the individual.


The obvious way to prevent fasting headaches is to not skip meals That being said, in unexpected circumstances — like an long work meeting or delayed flight — try even a little food intake or bite of sugar.

This could help ward off the headache.

If you are fasting for a longer period of time — like for religious reasons — consider reducing caffeine consumption weeks prior to fasting, followed by drinking a strong cup of coffee on the first day of the fast.

Alternatively, you can speak with your doctor about starting a preventive headache medication on the first day of your fast, like a long-acting NSAID. Remember, do not take any medications, including over-the-counter medications without the guidance of your physician.

Take Home Message

The exact cause behind fasting headaches is largely unknown and very well may involve many factors or be individualized.

Regardless, by being attune to your headache health, you can easily prevent this type of headache by making sure you are eating regular meals. Of course, if you are fasting for religious or other purposes, please speak with your doctor about the best strategy to prevent a fasting headache.


Awada A, al Jumah M. The first-of-Ramadan headache. Headache. 1999 Jul-Aug;39(7):490-3.

Headache Classification Committee of the International Headache Society. "The International Classification of Headache Disorders: 3rd Edition (beta version)". Cephalalgia 2013;33(9):629-808.

Torelli P, Evangelista A, Bini A, Castellini P, Lambru G, Manzoni GC. Fasting Headache: A Review of the Literature and New Hypotheses. Headache. May; 2009 49(5):744-52.

Torelli P, Manzoni GC. Fasting Headache. Curr Pain Headache Rep. 2010 Aug;14(4):284-91.

DISCLAIMER: The information in this site is for educational purposes only. It should not be used as a substitute for personal care by a licensed physician. Please see your doctor for diagnosis and treatment of any concerning symptoms or medical condition.

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