Is there a difference between being thirsty and dehydrated? Like scientifically, biologically – by the time you notice that you are thirsty, are you already dehydrated?

Question

Is there a difference between being thirsty and dehydrated? Like scientifically, biologically – by the time you notice that you are thirsty, are you already dehydrated?

In: Biology

Answer 1

If you want an easy to digest summary of the research (with citations) this is good:
https://fivethirtyeight.com/features/you-dont-need-8-glasses-of-water-a-day/

A lot of what people are claiming in either direction is not supported by science. 8 glasses a day is not supported. “If you are thirsty you are already dehydrated” isn’t either.