There’s a common misconception that caffeinated drinks like tea and coffee are dehydrating. This is largely due to their caffeine content, and the belief that caffeine consumption has a diuretic effect.
While there are no hard-and-fast answers, and there are a lot of variables to consider in your particular situation, research generally shows that caffeinated drinks like Green Tea are just as hydrating as non-caffeinated drinks, (or at worst, hydrate you ever so slightly less). Good news for tea lovers!