health 2026-04-29
Daily Water Intake by Age
How much water you actually need varies by age, body size, and activity.
"Drink 8 glasses a day" oversimplifies hydration. Real needs vary widely by individual.
Baseline by Age
US National Academies guidelines (total water from all sources, including food):
- Infants 0-6 months: 0.7 L (from milk)
- Infants 7-12 months: 0.8 L
- Children 1-3: 1.3 L
- Children 4-8: 1.7 L
- Boys 9-13: 2.4 L / Girls 9-13: 2.1 L
- Men 14+: 3.7 L / Women 14+: 2.7 L
About 20% comes from food. Pure drinking water target: roughly 2.5 L for men, 2 L for women.
Adjustments
- Hot climate or sweating: add 0.5-1 L per hour of activity
- Pregnancy: add ~0.3 L
- Breastfeeding: add ~0.7 L
- Fever, vomiting, diarrhea: add to replace losses
- High altitude: increased respiration loses water faster
Signs You Need More
- Dark yellow urine (target pale straw color)
- Dry mouth or lips
- Headache without other cause
- Fatigue or dizziness
- Less than 4-6 trips to the bathroom per day
Signs You're Drinking Too Much
Hyponatremia (low blood sodium) is rare but real. Endurance athletes drinking only water during long events have died. Symptoms: nausea, confusion, swelling. Drink to thirst plus electrolytes for events over 2 hours.
Caffeine and Alcohol
Both are mildly diuretic but coffee and tea still net hydrate. Alcohol nets dehydrates substantially; alternate with water.
Hydration Beyond Water
- Soup and broth
- Watermelon, cucumber, oranges (90%+ water)
- Yogurt and milk
- Herbal tea
Practical System
- Glass of water on waking
- Refillable bottle on desk
- Glass with each meal
- Extra during workouts
For activity tracking see [10000 steps myth fact](/blog/10000-steps-myth-fact).