The familiar “eight glasses” rule is a convenient reminder, not a universal medical requirement.
Some people need more and others need less.
Someone exercising heavily in hot weather may require much more fluid than a person spending the day indoors, while people with certain heart or kidney conditions may be advised to limit fluids.
If you have a medical condition that affects fluid balance, follow your healthcare professional’s recommendations rather than a general internet rule.
Is Coffee Dehydrating?
Coffee contributes fluid to your daily intake.
Caffeine can increase urination slightly, particularly in people who are not accustomed to it, but ordinary amounts of coffee do not automatically cancel out the fluid they provide.
Water remains an excellent everyday choice, especially when you are thirsty or losing extra fluid.
When You May Need More Fluids
You may need to increase fluid intake when you:
Exercise intensely
Sweat heavily
Spend time in hot weather
Have a fever
Have vomiting or diarrhea
Are recovering from illness
Vomiting and diarrhea can also cause electrolyte losses, so oral rehydration solutions may sometimes be more appropriate than plain water, particularly when fluid loss is significant.
When to Seek Medical Help
