Does Caffeine Dehydrate You? Not at Ordinary Intakes: in Trials, Coffee and Tea Hydrated About as Well as Water. The Extra Urine Shows Up at Big Doses.

Caffeine makes you pass a little more urine for a few hours: about 3.7 fl oz on average across 16 studies. At ordinary intakes the cup brings more water than that. In 50 men drinking four mugs of coffee a day for three days, body water, measured in 25 of them, was not significantly different from three days on water. Big doses at once are another matter.








