Can Dehydration Trigger a Migraine?
Medically reviewed by Linda Girgis | MD, Girgis Family Medicine on August 21st, 2026.
Yes, dehydration is a well-established migraine trigger that can cause severe headaches within hours. Studies show that even mild dehydration of 1.5% body weight loss can trigger migraines in susceptible individuals. When you're dehydrated, blood volume decreases and blood vessels in the brain may dilate or constrict abnormally, leading to the characteristic throbbing pain. Additionally, dehydration reduces electrolyte balance and can lower blood pressure, both contributing factors to headache onset. The American Migraine Foundation identifies dehydration as one of the top 10 migraine triggers, affecting approximately 1 in 3 migraine sufferers.
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