You’ve heard “eight glasses a day” since childhood. It’s tidy, memorable — and mostly made up. Real hydration needs swing wildly with your size, your food, your weather, and how much you move. Here’s the calmer, more honest version I give every client.
Start with your weight, not a slogan
A useful baseline is about 30–35 ml per kilo of body weight — roughly 2 to 2.5 litres for most adults. Then adjust: add half a litre for hard workouts, more in heat waves, and remember that soups, fruit, and vegetables quietly contribute a fifth of your intake.
Three signs you’re under-drinking
- The 3pm slump. Fatigue and foggy focus are thirst’s favorite disguises — try water before coffee.
- Headaches that arrive with the evening. A large glass of water at lunch prevents more headaches than painkillers fix.
- Dark morning urine. Pale straw by midday means you’re roughly on track — no app required.
“Drink to thirst, verify with your energy, and let food do a fifth of the work.”
Make it effortless
Keep a filled pitcher where you actually sit — visibility beats discipline. Flavor it with lemon, cucumber, or frozen berries if plain water bores you. And yes, coffee counts toward your total; it’s a mild diuretic, not a dehydrator.
Small habit, outsized payoff: clients who fix hydration first consistently report better sleep and fewer cravings within two weeks — before we change a single meal.
Written by Hannah Fennel
Registered nutritionist and founder of Fennelgrove Nutrition. Ten years helping busy people eat well without diets.
