Human Survival Limits: How Long Without Oxygen, Water, Food or Sleep

The human body can survive only a few minutes without oxygen; loss of consciousness can occur within 30 seconds to one minute, and permanent brain damage becomes likely after three to six minutes.

Without water, survival typically ranges from three to seven days, though extreme heat, physical exertion or illness can reduce this to one or two days.

When deprived of food but still hydrated, a person can live for several weeks, with estimates of three to eight weeks depending on age, health and body reserves.

Sleep deprivation impacts cognition quickly: after 24 hours attention, reaction time and mood decline, and after several days hallucinations, confusion and severe cognitive deficits may appear.