How long can you survive without sleep?

Sleep loss degrades function long before it threatens life. Twenty-four hours awake produces reaction times and judgement comparable to being legally drunk in most jurisdictions; by 48 hours, microsleeps intrude involuntarily and cannot be resisted by willpower. Beyond about 72 hours, perceptual disturbances and disordered thinking are common, and the brain begins taking sleep whether or not the person consents. There is no confirmed human death from voluntary sleep deprivation on its own — the real-world danger is what an impaired person does at a wheel or a machine, which kills a large number of people every year. Fatal familial insomnia, a rare inherited prion disease, does kill, but the sleeplessness there is a symptom of brain degeneration rather than the cause of death.

What happens, in order

Physiology, not instruction. Every figure here is a population range under particular conditions, and individual variation is large — temperature, exertion, fitness and health move all of them substantially. Nothing on this page is medical advice.

Going without something

• How long can you survive without water? About three days in mild conditions — but under a day in desert heat, and up to a week at rest in the cold.
• How long can you survive without food? Weeks rather than days — one to three weeks is typical, and water runs out long before calories do.
• How long can you survive without air? Consciousness goes in about a minute and brain injury begins around four to six minutes.
• How long can you survive without food and water? About three days — water sets the limit and food barely enters into it.
• How long can you survive without sunlight? Indefinitely, provided vitamin D comes from food or a supplement — sunlight itself is not a requirement.
• How long can you survive without human contact? Indefinitely in the direct sense — but isolation measurably raises the risk of dying early.
• How long can you survive without gravity? Indefinitely with exercise countermeasures — the record for one continuous flight is 437 days.
• How long can you survive without salt? Weeks to months at rest — kidneys are very good at conserving sodium — but days if you are sweating heavily.
• How long can you survive without vitamin C? Scurvy appears after roughly one to three months of near-zero intake, and is fatal in a few months more.
• How long can you survive without protein? Months, because the body cannibalises its own muscle — which is exactly why it eventually kills you.
• How long can someone with type 1 diabetes survive without insulin? Days. Missing insulin in type 1 diabetes is an emergency, not an inconvenience.