How long can you go without sleep

Questions about how long can you go without sleep usually point to documented human cases rather than a defined biological limit. Every duration on this page is what one person or one study sample recorded. None is a limit, a safe amount or a target.

The 1964 observation and multi-day records

In 1964 a Californian student, Randy Gardner, stayed awake for 264 hours, which is 11 days, and researchers observed him during the attempt. Guinness World Records reports that his record was broken two weeks later. Separately, a 2018 systematic review of sleep-deprivation studies lists a single-person laboratory case of 264 hours, reported in 1965, as the longest duration among the 21 studies it included ^[2][1].

As Guinness World Records recounts the 1964 case, the sleep researcher William Dement noted that Gardner's analytical abilities, perception, motivation, memory and motor control were affected to varying degrees, while John Ross, who observed him earlier in the attempt, reported hallucinations, delusions and an extremely short attention span by the fourth day ^[2].

Unmonitored totals and the presence of microsleeps

Guinness World Records no longer monitors the record for the longest time without sleep, citing the inherent dangers associated with sleep deprivation. The last holder it lists is Robert McDonald, at 453 hours 40 minutes in 1986, and it says no one is known to have broken that figure since ^[2].

CIBDOL · Unmonitored totals and the presence of microsleeps

Every long record carries a caveat about microsleeps. Guinness World Records gives them as one reason it cannot monitor the record: momentary lapses into sleep lasting a few seconds that cannot be monitored accurately without continuous physiological recording, and it writes that Dement later accepted that Gardner, although under constant supervision, probably experienced them. A 2025 narrative review describes microsleep episodes as short intrusions of sleep into wakefulness that the standard clinical scoring classification overlooks, and links them to attention lapses ^[2][3].

Why prolonged deprivation findings are historical

Most of what has been recorded about several days without sleep comes from older studies. The authors of a 2018 systematic review write that experiments with more than two nights without sleep, popular in the first half of the twentieth century, are no longer conducted because they are considered unethical, and in most countries prohibited by law, so they revisited historical studies: 21 studies of healthy people describing perceptual and psychological effects of sleep loss lasting from 24 hours to 11 nights ^[1].

In that review, changes appeared in an almost fixed order as time awake increased. All studies but one reported perceptual changes. Perceptual distortions, anxiety, irritability, depersonalisation and disorientation in time began within 24 to 48 hours of sleep loss, complex hallucinations and disordered thinking followed after 48 to 90 hours, and delusions after 72 hours. Visual changes were the most consistently reported, followed by bodily sensations and then hearing ^[1].

Performance changes within the first day

The effects start well before a record attempt. In a study of 39 people, 30 from the transport industry and 9 from the army, tested over 28 hours without sleep and separately after measured doses of alcohol, performance on some tests after 17 to 19 hours without sleep was equivalent to or worse than at a blood alcohol concentration of 0.05 percent, with response speeds up to 50 percent slower on some tests. After longer periods without sleep, performance reached levels equivalent to the highest alcohol dose given, about 0.1 percent ^[4].

A meta-analysis of 70 articles containing 147 cognitive tests, all on total sleep deprivation shorter than 48 hours, found effects ranging from small and non-significant for reasoning accuracy to large for lapses in simple attention. Of the moderators tested, only time awake was a significant predictor of the differences between studies, and only for accuracy measures ^[5].

Accumulated wakefulness and recovery

In a laboratory study of 48 healthy adults aged 21 to 38, which compared 14 days of restricted sleep with 3 nights without any sleep, lapses in alertness rose almost linearly with the cumulative time spent awake beyond about 15.84 hours, whichever way the sleep was lost, and 3 nights without sleep produced disproportionately large responses relative to the amount of sleep lost. In the restriction conditions, sleepiness ratings rose only slightly after the first days, which the authors read as participants being largely unaware of their growing deficits ^[6].

A period of normal sleep resolved the symptoms in many but not all of the reviewed cases. Some participants showed effects for days or weeks after a study ended, follow-up ranged from 1 day to 6 months, and the review's authors judged the data insufficient to say how much recovery sleep is needed ^[1].