Hi Jo, It all depends if the person you're speaking about has Congestive Heart Failure (CHF). A person's heart who has this condition is unable to pump optimally and thus fluid stays in the lungs causing a person to become short of breath. Typically their doctors limit the intake a person can have daily. A common misconception is that since they're on "water" pills like Lasix they can drink as much as they can because they'll just urinate it out. Not true....in that case the individual is not letting the medication do its job which is to get rid of the excess fluid from the body. I guess I ran off on a tangent, but in essence the answer to your question is "depends on what type of condition the person has".