If it is extreme it can harm your kidneys and you can wind up on dialysis. That's pretty rare.

The worst for me was 3 days on IVs and getting poked for labs frequently while some intern cut half my psych meds and nobody could figure out how or why and didn't get me back on what I needed so I couldn't sleep and wound up yelling at a dr on the phone at 2 AM after threatening to sign out AMA (would've if I hadn't had half my psych meds and couldn't drive).