Understanding Dehydration as a Headache Trigger

Treating and Preventing a Headache from Water Deprivation

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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 us quite quickly, and by the time we’re thirsty we may already be dehydrated, which can lead to a host of ailments, including headaches.

What Is Dehydration?

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

Dehydration is more likely to occur in warmer climates, at higher altitudes, with increased physical activity, and when someone is ill. Dehydration can have serious effects on our body, leading to unconsciousness and death in extreme cases. More commonly the symptoms of dehydration include thirst, fatigue, weakness, muscle pain, wrinkled skin, increased heart rate, and of course, headache.

What Is the Connection between Dehydration and Headaches?

Dehydration is a common underlying cause of headaches, and it’s also a common trigger for migraines. Headaches caused by dehydration can occur in the front or back of the head, or may be one-sided. Dehydration headaches also can be felt throughout the entire head, similar to a tension headache. A common symptom of dehydration headaches is an increase in pain when moving the head, especially during walking.

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, it results in a headache.

How Do I Avoid 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 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, it's 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.

This all being said, it is important to understand 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. Water can simply prevent a dehydration headache from occurring in the first place.

How Do I Treat 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.

Stay in a cool environment and rest so that the 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 to rehydrate quickly.

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 risk for water deprivation like on a hot day or when exercising.


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

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