Tea comes from the Camellia Sinensis plant, which is one of approximately 60 species of plants that naturally produce caffeine. This naturally stimulating chemical compound also acts as a diuretic. So logically speaking, it would stand to reason that tea may cause you to lose more water, than drinking something without caffeine.
Having said all that, the jury’s still out on whether tea actually causes dehydration. Studies over the years have been contradictory, but generally, it’s believed that you’d need to consume a lot of tea and, thus a lot of caffeine, for the diuretic effect to really impact you. Plus, tea is both delicious and refreshing, and if it encourages you to drink more than you normally would, then you’re likely increasing your water intake to start with. In short, it’s fine to drink tea in moderation, as part of an overall balanced and healthy diet.