Survival skills
A human being can survive an average of three to five days without the intake of water. The issues presented by the need for water dictate that unnecessary water loss by perspiration be avoided in survival situations. The need for water increases with exercise.
Suicide methods
Death from dehydration can take from several days to a few weeks. This means that unlike many other suicide methods, it cannot be accomplished impulsively. Those who die by terminal dehydration typically lapse into unconsciousness before death, and may also experience delirium and deranged serum sodium. Discontinuation of hydration does not produce true thirst, although a sensation of dryness of the mouth often is reported as "thirst." The evidence this is not true thirst is extensive and shows the ill feeling is not relieved by giving fluids intravenously, but is relieved by wetting the tongue and lips and proper care of the mouth. Patients with edema tend to take longer to die of dehydration because of the excess fluid in their bodies.