Understanding Dehydration as a Headache Trigger

Treating and Preventing a Headache From Water Loss

Woman drinking water from glass, close-up, profile
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While most of us know the adage about drinking six to eight glasses of water each day, the truth of the matter is that many of us don’t follow through on it.

Dehydration can sneak up on you quite quickly. In fact, by the time you're thirsty, you may already be dehydrated, which can lead to a host of ailments, including headaches.

Basics of Dehydration

Dehydration occurs when the body loses more water (through processes like sweat or urine) than it takes in.

Often times, the term dehydration is used interchangeably with volume depletion (called hypovolemia). Technically speaking, dehydration occurs from water loss alone whereas hypovolemia occurs with any loss in blood volume in the body, either through water loss alone or through salt and water loss (for example, vomiting or diarrhea). 

Regardless, dehydration (or hypovolemia) is more likely to occur in warmer climates, at higher altitudes, with increased physical activity, and when someone has a fever. Dehydration is also more common in infants and children because they are smaller, are more prone to viruses that cause vomiting and diarrhea, and may not be able to communicate that they need water or are thirsty. 

Symptoms and Signs of Dehydration

While dehydration can be mild, it can also be severe, leading to serious effects like unconsciousness and death in extreme cases. Whereas mild dehydration may not initially cause any symptoms, as it progresses, these symptoms and signs may occur:

  • Thirst
  • Fatigue and weakness
  • Muscle pain
  • Wrinkled skin
  • Increased heart rate
  • Headache
  • Dark yellow urine or urinating less frequently than usual
  • Feeling dizzy or like you might faint
  • No tears when crying
  • Eyes that appear sunken in the face
  • Dry mouth or cracked lips

Connection Between Dehydration and Headaches

Dehydration is a common underlying cause of headaches, and it’s also a common trigger for migraines.

Migraine headaches are often one-sided, throbbing, and associated with nausea, vomiting, and a sensitivity to light and/or sound.

Dehydration, though, may also lead to a headache that resembles a​ tension headache, so it's felt all over the head. A common symptom of dehydration headaches is an increase in pain when moving the head.

It’s not entirely clear why dehydration causes a headache. Some studies have shown that blood vessels in the head may actually narrow in an attempt to regulate body fluid levels. Because this would make it harder for oxygen and blood to get to the brain, a headache results.

Avoiding a Headache From Dehydration

Ensuring that your body gets enough fluids is the best way to avoid a dehydration headache. Some useful tips include:

  • Take in as much liquid as you need to not feel thirsty.
  • Drink enough water so that your urine is a light yellow or clear color.
  • Remember that not all fluids are created equal. Alcohol and drinks containing caffeine, such as coffee, actually function as a diuretic. This means that they cause you to lose fluid.
  • Recognize that if you are overweight, live in a warm climate, are at a higher altitude or engaged in a strenuous physical activity, you may require more water intake than the recommended eight glasses of water.
  • Keep in mind that consuming more fruits and vegetables is a way to increase your water intake. That being said, eating these nutritious foods is not a supplement for drinking pure water.
  • Seek out shade when it's hot out, plan outside activities for cooler parts of the day, and hydrate in advance of any sporting or active event.

Lastly, it's important to note that increasing your overall water intake throughout the day has not been found to reduce the total number of headaches a person experiences in general.

Even so, drinking water regularly may help you feel better and stave off head pain when it comes to your headache and migraine health.

It's worth a try, especially since it costs nothing and is non-invasive and simple. 

Treating a Headache From Dehydration

To treat headaches triggered by dehydration, the body needs to become hydrated again. Drinking water should make you feel better within a half hour or so. Although for some people it may take up to three hours. Sometimes sports drinks or Pedialyte for children may be a good option because they provide electrolytes and carbohydrates to help absorb water better.

In addition, be sure to stay in a cool environment and rest, so that your body is able to rehydrate without sweating. If the dehydration is severe, you cannot keep fluids down, or if your headache doesn't subside, go to a hospital so you can be placed under the care of a doctor. In these instances, you will likely receive fluids through the vein (called intravenous fluids) to rehydrate quickly.

Likewise, be sure to call your child's doctor if he or she is experiencing vomiting that lasts for more than one day or diarrhea that lasts more than a few days. Other reasons to call your doctor are:

  • If your child cannot keep any fluids down or has not been drinking for many hours.
  • If your older child has not urinated in the last six to eight hours, or if your baby or toddler hasn't had a wet diaper in four to six hours.
  • There is blood in your child's vomit or stool.

A Word From Verywell

Keep in mind that prevention is the best treatment for a dehydration headache. So do what it takes to incorporate water drinking into your everyday routine, especially when you are at risk for water loss like on a hot day or when exercising. 

The last tidbit is if you continue to develop headaches or migraine from dehydration, talk with your doctor about potential causes. Certain medications (for example, diuretics) could be the culprit behind your headaches. 

Sources:

Popkin BM, D'Anci KE, Rosenberg IH. Water, hydration and health. Nutr Rev. 2010 Aug;68(8):439-58.

Price A, Burls A. Increased water intake to reduce headache: learning from a critical appraisal. J Eval Clin Pract. 2015 Dec;21(6):1212-8.

Spigt M, Weerkamp N, Troost J, van Schayck CP, Knottnerus JA, A randomized trial on the effects of regular water intake in patients with recurrent headaches. Fam Pract. 2012 Aug;29(4):370-5.

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

Somers MJ. (2017). Clinical assessment and diagnosis of hypovolemia (dehydration) in children. Mattoo TK, Kim MS, eds. UpToDate. Waltham, MA: UpToDate Inc. 

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