Does tea cause dehydration?

It used to be believed by many that tea caused some level of dehydration, but that myth has been discredited, according to WebMD. The main reason people believed that tea caused dehydration is because of its natural diuretic effect, which causes more frequent urination.

The diuretic effect caused by drinking tea does not have a negative effect on hydration, according to WedMD. Water and black tea are not much different in the way that they maintain regular hydration in human subjects. A randomized controlled study showed that healthy males remained hydrated even when consuming only black tea and no water for a period of 12 hours.