Water Impact 0 by (Henningklevjer) - (Henningklevjer). Licensed under Creative Commons Attribution-Share Alike 2.5 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Water_Impact_0.jpg#mediaviewer/File:Water_Impact_0.jpg
Common signs of dehydration include: feeling thirsty; dark urine and not passing much urine when you go to the toilet; headaches; lack of energy; feeling lightheaded.