Medical Education Notice: This guide is synthesized from clinical guidelines for patient education and is not a substitute for diagnostic medical evaluation or individualized treatment by a licensed physician.
Nutrition
5 min readReviewed Sep 2026Hydration, Explained in Plain Language
Quick Answer (TL;DR)
Most adults need roughly 1.5 to 2.5 litres of fluid a day from all drinks and food, adjusted for heat, activity and body size.
What It Means
The often-repeated eight glasses rule is not based on strong evidence. Tea, coffee, milk and water-rich foods all count toward your intake.
Why It Matters for Your Health
Even mild dehydration affects concentration, headaches, constipation and exercise performance, and repeated dehydration raises the risk of kidney stones and urinary infections.
Recommended Biomarker or Metric to Track
Log daily intake for a week to see your real baseline, not your intention.
Questions to Ask Your Doctor
Targeted questions based on latest clinical consensus statements.
1Is there a fluid target or limit that applies to me?
2Could a medication such as a diuretic change my needs?
3Do my symptoms suggest dehydration or something else?
4Should I be concerned about kidney stones?
5What signs mean I should seek help?
NHS - Water, drinks and your health
European Food Safety Authority - Dietary reference values for water
CDC - Water and healthier drinks
Suggest a Medical or Clinical Correction
Healthovi content is continuously reviewed. If you notice outdated recommendations or clinical ambiguities, let our medical review board know.