Dehydration and Migraine: How Much Water Do You Actually Need?

"Drink more water" is some of the most repeated migraine advice out there — and also some of the most vaguely explained.

How much is actually enough?

And does it really make a meaningful difference?

Why Dehydration Matters for Migraine

Dehydration is a well-recognised contributing factor for migraine.

Even mild dehydration can affect blood volume and circulation, and some research suggests it may influence brain function in ways relevant to migraine, including effects on the same sensitised pathways involved in attacks.

The tricky part is that dehydration's effects can be subtle and easy to miss — you don't need to feel obviously thirsty to be running on a meaningful fluid deficit, particularly if you're also dealing with the nausea that often accompanies migraine, which can itself reduce how much you drink.

How Much Water Do You Actually Need?

General guidance suggests around 33ml per kg body weight per day for most adults, though this varies depending on body size, activity level, climate, and individual factors.

Rather than fixating on a precise number, a more practical guide is your urine colour — pale yellow generally indicates adequate hydration, while darker yellow suggests you need more fluids.

Practical Ways to Improve Hydration

Start your day with water before caffeine. A glass of water first thing, before your coffee or tea, helps offset the mild dehydrating effect caffeine can have and sets a better baseline for the day.

Keep water visible and accessible. Simply having a water bottle within reach significantly increases how much most people drink — removing the friction of needing to get up and find it.

Build hydration into existing habits. Pairing a glass of water with something you already do regularly, each meal or each time you sit down at your desk, creates an easy, sustainable habit rather than relying on remembering throughout the day.

Find alternatives if you don't enjoy plain water. Adding a slice of lime, lemon, or cucumber, or trying soda water with a splash of lime juice, can make hydration more appealing if plain water feels unappetising — and can double as a satisfying alternative if you're also trying to reduce alcohol intake.

Watch electrolytes during hot weather or intense exercise. In conditions where you're losing more fluid through sweat, water alone may not be enough — electrolyte balance matters too, particularly sodium, potassium, and magnesium.

A Word of Caution

While good hydration is genuinely worth prioritising, it's not a singular fix, and significantly overhydrating isn't beneficial either.

Like most of the factors discussed on this blog, hydration is one piece of your overall threshold — worth getting right, but not something to obsess over in isolation from sleep, stress, and the other contributing factors.

The Bigger Picture

Dehydration is one of several biological load factors covered in Week 7 of Raise Your Threshold, my 8-week program — alongside diet, magnesium, and blood sugar stability, as part of building your overall threshold rather than fixating on any single factor.

Learn more →