Hydration: the most underrated habit
Not drinking enough can make headaches, fatigue and constipation worse.
The essentials
About 30 to 35 ml of water per kilo a day, or 2 to 3 L for most adults, spread from morning to dinner.
A big glass of water when you wake up: overnight sleep naturally dehydrates you.
When appetite drops, thirst often drops too: drink on a schedule, not by thirst.
Add electrolytes (sodium, potassium, magnesium) on hot days or training days.
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Based on your goal
Choose your goal: here is what matters most for it.
Weight loss
- Thirst is often mistaken for hunger: a glass of water before snacking clears up the signal.
Performance
- 1% dehydration means a measurable drop in strength and endurance.
Focus & cognition
- Just 2% dehydration is enough to hurt attention and working memory.
Sleep
- Front-load your water earlier in the day to avoid nighttime bathroom trips.
Energy
- Midday fatigue is often mild dehydration before it's a caffeine shortage.
Longevity
- Steady hydration supports kidney and cardiovascular function: two pillars of healthy aging.
Joints & mobility
- Cartilage is about 70% water: staying hydrated helps keep joints comfortable.
Digestion & inflammation
- Fiber without water causes constipation: every increase in fiber needs to come with more water.
Skin & appearance
- Skin hydration starts from the inside: water before creams.
Stress & calm
- Dehydration raises cortisol: a body low on water is a body on alert.
In detail
The simple method
A large glass when you get up, a glass before each meal, a one-litre bottle to finish before noon and another before dinner: fixed anchors, no app or math. Pale yellow urine means you're on target; dark all day is a signal to correct.
Electrolytes, coffee and tea
On a hot day, during hard training, after very low-salt meals or a digestive upset: add a pinch of sea salt to your water, a potassium-rich food (banana, potato, legumes) or a sugar-free electrolyte mix.
Drinking a lot of plain water while sweating heavily can dilute the sodium in your blood. Coffee and tea count partly and herbal tea fully; alcohol dehydrates, so have a glass of water with each drink.
Spotting mild dehydration
A dull headache late in the day, an afternoon slump, trouble concentrating, dizziness when standing up, constipation: at the first of these signs, drink a large glass of water first.
Common mistakes
- Chugging 2 liters at once in the evening to "catch up" on the day.
- Increasing fiber without increasing water: constipation is a sure thing.
- Waiting to feel thirsty: when appetite drops, thirst often shows up too late.
- Letting a headache drag on despite good hydration: it should be reported (Side effects page).