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Dehydration Headaches: Causes and Prevention

There’s a simple solution to help prevent dehydration headaches – drinking more water. But how much H2O is enough?

This situation may sound familiar: you’ve been running around all day, so busy that you haven’t even been able to take a break and have a glass of water. You keep going despite the drought in your mouth until, suddenly, pain radiates across your forehead.

What you are experiencing is common – it’s a dehydration headache.9 But how can dehydration cause headaches? Learn more below.

What is a dehydration headache?

A dehydration headache is exactly what it sounds like: a headache caused by a lack of fluids in the body. They are classified as ‘secondary’ headaches, which are headaches caused by external factors – like injury or illness. This makes them different from ‘primary’ headaches (such as migraines, cluster or tension-type headaches), which aren’t caused by another condition.1

Headaches are a common symptom of dehydration, even if it is only mild to moderate. In fact, being dehydrated can also trigger other types of headaches, including migraines.2

How does dehydration cause headaches?

Every day, our body is stuck in a battle to retain the right balance of water and electrolytes, to make sure it can function properly. This is because we constantly lose fluid during the day through normal bodily functions such as urine, sweat and saliva – so it’s important that we consistently replace that fluid.2 When the human body loses more fluid than it retains, it will become dehydrated.

If your body does become dehydrated, you may experience a variety of different symptoms, including increased thirst, a dry mouth, dark colored urine, fatigue or dizziness – and, of course, a headache.2

Dehydration and headaches – Risk factors

If you experience a dehydration headache, it is because your body has lost too much fluid.2 Some common risk factors for dehydration are:

  • Not drinking enough water, or eating enough food
  • Excess sweating due to increased exercise or heat
  • Vomiting, diarrhea or fever (caused by a stomach flu or other condition)

Since roughly two-thirds (60%) of the adult human body is made up of water, it’s easy to see why losing fluids may hamper bodily functions.3 But there are certain people in the population who may be at greater risk of dehydration and dehydration headaches, including infants and children, the elderly and people with a chronic illness.4

Dehydration headache location – What does a dehydration headache feel like?

Because headaches are a common symptom of many different conditions, it can sometimes be difficult to figure out whether the pain in your head is being caused by dehydration or by something else. Pinpointing the location of your headache pain may offer some clues.

Dehydration headaches may cause pain on all sides of your head, while a migraine may only cause intense pain on one side of the head and will often be accompanied by symptoms of nausea, vomiting, or light and sound sensitivity.5 Dehydration headaches will also feel different from a sinus headache, as dehydration headaches do not cause pressure or pain in the face, while sinus pressure headaches do.6

Another simple way to identify a dehydration headache is to check for other common dehydration symptoms. If you suspect that you have a dehydration headache, you will likely also experience some or all of these symptoms in addition to your headache:2

  • Increased thirst
  • A dry mouth
  • Dark yellow-colored urine or decreased urination
  • Fatigue or lethargy
  • Dizziness (particularly after standing up)
  • Irritability
  • Loss of elasticity in the skin

How to help get rid of a dehydration headache

You probably already know the laundry list of reasons why drinking water is essential for our everyday health: it helps flush out toxins, regulates our body temperature, protects important tissues and joints in the body, and much more.7 But keeping your water bottle topped off also helps to manage and prevent dehydration headaches.2

Yes, the first thing to do if you feel dehydration pain sweeping across your forehead is to reach for some water to help replace those lost fluids and balance electrolytes.2 While you may be tempted by a sports drink instead, don’t use these as a replacement for water. Many sports drinks are high in sugar or salt and will not adequately restore your electrolyte balance. In fact, some of these drinks may actually increase your dehydration.2

But how much water should you actually be drinking each day?

Unfortunately, there is no one-size-fits-all answer to this question. According to Harvard Medical School, most healthy adults need to drink roughly eight glasses of water per day (a common number you’ve probably heard before). However, this may change depending on your body size, environment or the amount that you exercise daily.8 For the best guidance on how much water a day is right for you, speak to your doctor.

Learn more about headache prevention techniques.

Easing dehydration headache pain – How Excedrin® can help

Of course, the first step to getting rid of your dehydration headache is drinking water. However, if you want some quick pain relief, try an over-the-counter pain relief medication like Excedrin® Extra Strength.

Excedrin® combines three active ingredients to form a strong and effective headache medicine. For some, headache relief starts in 15 minutes – so you can get back to your day fast. Always use medication as directed.


  1. Secondary Headaches. American Migraine Foundation. American Migraine Foundation. Accessed 27/05/20.
  2. Headaches and dehydration. National Headache Foundation. Accessed 27/05/20.
  3. Water and the Human Body. United States Geological Survey. Accessed 27/05/20.
  4. Dehydration (Symptoms & causes). Mayo Clinic. Accessed 27/05/20.
  5. Migraine. The Migraine Trust. Accessed 28/05/20.
  6. Sinus Headaches. Cleveland Clinic. Accessed 28/05/20.
  7. Water and Nutrition. Centers for Disease Control and Prevention. Accessed 28/05/20.
  8. Water and health: follow your thirst. Harvard Medical School. Accessed 28/05/20.
  9. Water-deprivation Headache: A New Headache With Two Variants. National Library of Medicine, National Center for Biotechnology Information. Accessed 03/07/20.

References:  headache relief, headache prevention, hydration

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