Can Dehydration Cause a Headache?
Medically reviewed by Linda Girgis | MD, Girgis Family Medicine on August 21st, 2026.
Yes, dehydration is a common and well-established cause of headaches. When your body loses more fluids than it takes in, blood volume decreases and blood vessels in the brain can constrict, triggering pain. Studies show that even mild dehydration of 1-3% body weight loss can cause headaches in many people. The headache typically develops gradually and may be accompanied by other symptoms like fatigue, dizziness, and difficulty concentrating. Dehydration headaches often feel like a dull, throbbing pain that worsens with movement. Drinking 16-20 ounces of water usually provides relief within 30 minutes to 3 hours, making proper hydration both a treatment and prevention strategy.
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