From the Research
Dehydration causes headaches primarily because it reduces blood volume, leading to decreased blood flow to the brain, and disrupts electrolyte balance, which can trigger pain receptors in the meninges and cause vascular strain. When your body lacks adequate fluids, your brain can temporarily contract or shrink from fluid loss, causing it to pull away from the skull and triggering pain receptors in the meninges (the protective layers surrounding the brain) 1. Additionally, dehydration concentrates blood vessels, requiring your heart to work harder to pump oxygen and nutrients to your brain and other organs. This vascular strain can trigger headache pain. Dehydration also disrupts electrolyte balance, particularly sodium and potassium, which are essential for proper nerve and muscle function, including those in your head and neck.
Some key points to consider when evaluating the relationship between dehydration and headaches include:
- The effects of dehydration on brain morphology, including ventricular expansion and changes in brain volume 2
- The impact of dehydration on pain thresholds and cortical activations in response to pain, compared with rehydration 3
- The importance of maintaining euhydration to prevent dehydration headaches, particularly in individuals with underlying medical conditions or those who are prone to dehydration 1
To prevent dehydration headaches, it is essential to drink enough water throughout the day, aiming for at least 8-10 cups (64-80 ounces) daily, and more during hot weather, illness, or physical activity. If you already have a dehydration headache, drinking water slowly but steadily, and considering adding electrolytes through sports drinks or foods like bananas, can help alleviate symptoms. Most dehydration headaches resolve within 30 minutes to 3 hours after rehydrating properly.