About 6 to 8 cups or glasses of fluid a day is the standard guide - and that is total fluid: tea, coffee, milk, juice, and watery food all count.
Your real need scales with heat, exercise, pregnancy or breastfeeding, fever, vomiting, or diarrhea. The practical test is urine color: pale straw is hydrated, dark yellow means drink more. Thirst works for most healthy adults, but it lags in older people, who should drink on a schedule. There is no evidence behind forcing plain water constantly - and truly overdoing it in a short window can dilute blood sodium dangerously. Pymander is a free AI doctor, 24/7 by text, for specific situations like illness or training.
What to do
Common questions
How much water should you drink a day?
The standard guide is 6 to 8 cups or glasses of fluid a day - that is the UK Eatwell Guide recommendation, and it lines up with the common advice you will see elsewhere. Two things most people get wrong about it: first, it is total fluid, not just plain water - tea, coffee, milk, juice, and even watery food like fruit and soup all count (yes, coffee counts; its mild diuretic effect does not cancel the fluid). Second, it is a guide, not a quota - your real need scales with heat, exercise, pregnancy or breastfeeding, fever, vomiting or diarrhea, and body size. The practical test beats counting: urine color. Pale straw means you are hydrated; dark yellow means drink more; totally clear all day may mean you are overdoing it. Thirst is a decent guide for most healthy adults, though it lags in older people, who should drink on schedule rather than on thirst. The 8-glasses-of-plain-water-plus-more myth, and the idea that you must force water constantly, have no evidence behind them - and genuinely overdoing plain water in a short window (think hours, not days) can dangerously dilute blood sodium, which endurance athletes learn the hard way. Pymander is a free AI doctor, 24/7 by text, that can help you think through specific situations like illness or training.