Dehydration and headaches

Can dehydration cause headaches?

Dehydration headaches are fairly common and can be tedious to get rid of. But what, if any, is the scientific evidence linking dehydration and headaches? How can you spot and alleviate a headache caused by dehydration?

dehydrationYour body requires the right balance of fluids and electrolytes to function properly. When your intake of water, salts, and sugars becomes unbalanced, symptoms may include vomiting, diarrhea, or sweating, all of which affect mood and day-to-day well being. A headache may be a key symptom of this lack of fluid and electrolyte balance.  



Can dehydration cause headaches? 

Evidence shows that for many people there is a link between water deprivation and headaches. A survey of people who were dehydrated showed that 1 in 10 of the subjects had a headache and many of them also had impaired concentration and increased irritability. The severity of the headache was associated with the duration the participants went without water. Furthermore, the headaches were relieved 30 minutes after rehydration with water: the survey reported that most people’s symptoms were relieved 30 minutes after rehydrating [1]. In a study of 102 patients complaining of recurrent headaches, it was found that increasing their water intake improved their self-reported headache symptoms [2].



Headaches from Dehydration

dehydration and headaches

A possible physiological cause of headaches from dehydration is the change that happens to your blood when you don’t drink enough fluids. In 1980, a study measured the contents of the blood in people who had not had water for 24 hours. They discovered that the volume of plasma (the liquid which carries platelets, white and red blood cells) in the blood had significantly decreased, causing the solutes dissolved in the blood to be more concentrated. In addition, the concentration of sodium increased by 2.1% [3]. The concentration of the blood went back to normal once the participants had rehydrated.

There are many theories as to why the changes to the blood causes headaches. One theory is that the high concentration of sodium and other substances dissolved in the blood can have an effect on flow of blood through the brain. This could potentially lead to pain and pressure in the head. This is only one of many hypotheses but is supported in findings in animals [4].



What are the symptoms of a dehydration headache? 

Headaches due to dehydration can be caused by pain involving the whole head. You can even experience pain and pressure in the face. In addition to a headache, you may experience thirst, confusion, fatigue, dizziness, increased heart rate, low blood pressure, and reduced urine output [5].



Dehydration and alcohol hangovers 

dehydration and alcohol

Alcohol hangovers may also lead to headaches resulting from dehydration. Symptoms may include nausea and a reduced cognitive and spatial performance. These effects can be caused by dehydration, hormonal alterations, dysregulated cytokine pathways (chemical messengers secreted by cells of the immune system, resulting in an effect on other cells) and toxic alcohol effects. Alcohol hangover results in increased levels of a hormone called ADH. Releasing ADH is the body’s way of stopping too much water being lost in the urine. When you consume alcohol, ADH stops working in the kidneys, which causes your body to start producing too much urine and losing too much fluid [6]. This can result in dehydration and the headache experienced while hungover.

There are clear links between dehydration and headaches. Be sure to rehydrate properly—especially after exercise, hot days, or drinking alcohol to try to reduce the painful symptoms of dehydration.  

Writer: James Gunnell
Editor: Elizabeth Trelstad,


1. “Water-Deprivation Headache: A New Headache With Two Variants” Blau. J., Kell. C. and Sperling J. The Journal of Head and Face Pain. 2004. A survey to find out the prevalence and quality of headaches induced by water deprivation in a group of medical students, doctors, and their family members.
2. “Increased water intake to reduce headache: learning from a critical appraisal” Price. A and Burls. A. Journal of Evaluation in Clinical Practice. 2015. A study investigating the therapeutic effect of increasing water intake in dehydrated patients suffering from headaches.
3. “Thirst following water deprivation in humans” Rolls. R et al. American Journal of Physiology. 1980. A study of the physiological effects of dehydration on blood contents and the course of recovery after the 24 hours of water deprivation.
4. “Bulk flow of cerebrospinal fluid into brain in response to acute hyperosmolality” Pullen.
R., DePasquale. M. and Cserr. H. American Journal Of Physiology. 1987. An experiment in which the content of cerebrospinal fluid bathing the brain of mice was manipulated to record the and the flow of fluid in the brain.
5. “Dehydration headaches: Signs, treatment and prevention” Fletcher. J. Medical News Today. 2017. An easily accessible article describing the signs and causes of dehydration induced headaches.
6. “The Alcohol Hangover” Wiese. J., Shlipak. M. and Browner. W. Annals of Internal Medicine. 2000. A review of the scientific literature on the epidemiology, characteristics, and causes of alcohol induced hangover.

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