Hydration Advice: Separating the Useful From the Overstated

The familiar eight-glasses rule has thin origins. Current guidance is more flexible.

Few wellness rules are repeated as often as eight glasses of water a day, yet its evidence base is limited.

Health authorities generally give total fluid intake ranges that include water from food and other beverages, including tea and coffee.

Needs vary with climate, activity, body size and health conditions, so a single number does not fit everyone.

For healthy adults, drinking to thirst and noting pale urine colour are commonly cited practical guides. People with kidney or heart conditions should follow clinician advice.

Editorial note: this article summarises published research for general information. It is not medical advice. Discuss any intervention with a qualified clinician.