How long can you survive without vitamin C?

Humans are among the few mammals that cannot make their own vitamin C, because the gene for the final enzyme in the pathway is broken in our lineage. The body holds a pool of roughly 1,500 mg when replete, and symptoms begin once that falls below about 300-400 mg, which takes one to three months on essentially none. Vitamin C is required to build stable collagen, so the failures are structural: gums bleed and teeth loosen, old wounds and even old fractures reopen, capillaries leak and produce bruising, and the person becomes profoundly weak. Untreated it kills, usually through haemorrhage or infection, which is why it emptied so many ships in the age of sail. It is also one of the fastest reversals in medicine — a few days of citrus or a supplement turns it around.

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 sleep? No one has died of sleep deprivation alone; the record is 11 days, and severe impairment arrives within two.
• 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 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.