A January 2014 study published in the journal PLOS ONE has found that, contrary to what many people think is true, your morning cup (or cups) of Joe will not dehydrate you. In fact, moderate coffee consumption will keep you just as hydrated as if you were to drink water instead, the study concludes. That means you can have four cups of coffee without your levels getting thrown off.
MORE: No, Coffee Will Not Dehydrate You