Migraine or dehydration headache: how to tell them apart
by AUA Hydrate
«I have a migraine.» We say it for just about any headache. Yet migraine is a precisely defined neurological condition with its own criteria — and a good share of what gets called that is something else. Often it is a dehydration headache: more ordinary, and far easier to avoid.
⏱️ The essentials
- Migraine is a neurological condition: throbbing pain, often one-sided, nausea, sensitivity to light and sound.
- A dehydration headache is diffuse, dull, without nausea, and usually eases within hours of rehydrating.
- For people who get migraines, lack of water is among the most commonly reported triggers — without being the cause of the condition.
Two different things, often confused
The distinction is not a matter of vocabulary: it changes entirely what there is to do.
| Dehydration headache | Migraine | |
|---|---|---|
| Location | Diffuse, both sides, often forehead and temples | Frequently one side only |
| Type of pain | Dull, pressing, band-like | Throbbing, in time with the heartbeat |
| Intensity | Mild to moderate | Moderate to severe, worsened by movement |
| Accompanying signs | Thirst, dry mouth, dark urine, fatigue | Nausea, light and sound sensitivity, sometimes aura |
| Duration | Usually eases a few hours after drinking | 4 to 72 hours untreated |
One important point: migraine is a medical condition, not simply an intense headache. Drinking water does not cure it, and attacks that keep coming back call for medical follow-up — effective treatments exist. What follows concerns hydration: one factor among several, not a remedy.
Why lack of water causes headaches
When the body dehydrates, blood volume drops slightly. The brain receives a little less oxygen and fewer nutrients, and the vessels respond by dilating — enough to trigger pain. In parallel, falling sodium and potassium disrupt nerve transmission, the same mechanism behind cramps described in Muscle cramps and headaches.
That is why a dehydration headache often turns up late in the day, after several hours without drinking, or on waking after a short night. And why it eases relatively quickly once balance is restored.
Among migraine sufferers, one of the most frequent triggers
People who live with migraine regularly name dehydration among the factors that set off an attack, alongside lack of sleep, stress, skipped meals and hormonal shifts. That does not mean drinking more eliminates migraine: it means one avoidable trigger fewer is one occasion fewer.
That is where the practical value lies. Of all the known triggers, hydration is by far the easiest to control. You do not choose your hormonal cycle or your workload; you can choose to drink steadily.
Five things that make a difference
- Drink before you feel thirsty. Thirst is a late signal: by the time it shows up, dehydration has already begun.
- Spread it across the day rather than catching up in the evening. The subject is developed in How much water should you really drink each day.
- Watch the colour of your urine. Pale straw is good. Dark means you are already late.
- Replace what you lose after exercise, in heat, or after a short night — not just water, minerals too.
- Keep a three-week diary if attacks recur: sleep, meals, stress and fluids. It is the only way to find out which trigger actually applies to you.
💡 The AUA tip: the moments when a dehydration headache is likely are fairly predictable — end of the day, after exercise, the morning after a short night. Exactly the ones set out in When to take electrolytes. One stick in 500 ml of water, sugar-free, makes water pleasant enough that you drink it before the pain arrives rather than after.
Stay ahead of thirst
Sugar-free, 2 kcal, one stick in 500 ml of water: discover our three flavours.
Frequently asked questions
How do I know if my headache comes from dehydration?
Three signs pointing the same way: you have drunk little for several hours, the pain is diffuse rather than one-sided, and it eases noticeably within two to three hours of drinking properly. If it throbs on one side with nausea, that is a different picture.
Does drinking water stop a migraine already underway?
No. Once the attack has started, hydration does not interrupt it. Its role is upstream, on the triggers.
Does coffee cause headaches?
Its diuretic effect is modest at usual doses. Stopping abruptly after regular consumption, however, causes a well-documented withdrawal headache — often mistaken for a weekend migraine.
