Because of the caffeine, coffee is both a natural diuretic and a bladder stimulant, urologist Vannita Simma-Chiang, M.D., previously told mbg, and tea has a similar effect. While that’s true, the diuretic effects are mild, and research shows that coffee and tea—despite common misconceptions—are not actually dehydrating1 when they’re consumed in moderation. That said, drinking multiple cups of coffee or tea without also drinking water could end in dehydration. “A cup of coffee is not going to dehydrate you that much,” integrative medicine doctor Bindiya Gandhi, M.D., says, “but many cups of coffee without water intake will.” Dry, chapped lips could be a sign you’ve gone overboard, gastroenterologist Will Bulsiewicz, M.D., MSCI, previously explained. Other signs of dehydration include dark yellow urine and not feeling an urge to pee often enough. Summary: One cup of coffee would count as about half a glass of water. While these numbers are not based on an exact science, Waldrop says they can be used as general guidelines to make sure your fluid intake is sufficient. Summary: One cup of tea would count as about three-quarters of a cup of water. It may be surprising that milk would be a good source of hydration, but it has been shown in some studies to promote rehydration after exercise2—even more successfully than some sports drinks. “Even though lattes would contain less coffee, for reference, I’d still count them as about half [the volume of water],” Waldrop says. Try to keep those lattes unsweetened, though, as some coffee beverages can pack in a lot of added sugar, which may affect optimal hydration3. For other ways to stay hydrated, be sure to drink plenty of water—especially when you’re exercising, sick, or in any other situation where you may be losing fluids. Eating hydrating or electrolyte-rich foods can also count toward and benefit overall hydration levels.
