No one knows the limit, because experiments beyond 48 hours are considered unethical, and the longest documented stretch is a single case of 264 hours (11 days) in 1966. What studies do show is that performance falls long before that: after 17 to 19 hours awake it was equal to or worse than a blood alcohol level of 0.05% on some tests, and perceptual distortions and irritability start within 24 to 48 hours. This page reports findings; it is not a guide to staying awake.
How long can the human body go without sleep? Nobody knows the limit, because experiments beyond 48 hours are now considered unethical, and the longest documented case is a single person awake for 264 hours, 11 days, in 1966. What research can say is how much worse you function at each stage on the way: the first measurable losses come after about 16 hours, so the practical version of the question is how long without sleep before it costs you something.
This page collects what controlled studies found at roughly 17, 24, 36, 48 and 72 hours without sleep. It is a summary of findings, not a guide to staying awake, and it does not make the record look like something to try. For the symptoms of ordinary short sleep, sleep deprivation symptoms goes through them, and the rare inherited disease that truly stops sleep is covered in fatal familial insomnia, which is unrelated to staying up by choice.
How long can the human body go without sleep? The documented limit
How long can humans go without sleep in the record books? A 1966 report in Archives of General Psychiatry describes psychiatric and EEG observations on a case of prolonged wakefulness of 264 hours, which is 11 days. It is a single observed case, not a trial, and nobody should read it as a safe limit. A 2018 systematic review explains why there are so few such data: sleep deprivation beyond 48 hours is considered unethical today, so the review had to go back to historical studies.
Gulevich G, Dement W, Johnson L. Psychiatric and EEG observations on a case of prolonged (264 hours) wakefulness. Arch Gen Psychiatry 1966. PMID 5939071
That review identified 21 eligible studies of healthy people (760 participants in total, with sleep loss from 24 hours to 11 nights, on average 72 to 92 hours without sleep). Researchers today rarely ask volunteers to stay awake 48 hours or more. So how long can you stay up without sleep? The studies answer with what happens along the way, not with a hard stop.
Waters F, Chiu V, Atkinson A, et al. Severe Sleep Deprivation Causes Hallucinations and a Gradual Progression Toward Psychosis With Increasing Time Awake. Front Psychiatry 2018. PMID 30042701
How many hours should you be awake? Where performance starts to fall
How many hours should you be awake before it costs you something? A dose-response experiment in 48 healthy adults aged 21 to 38 is the clearest answer. Participants had time in bed of 4, 6 or 8 hours for 14 days, or no sleep for 3 nights. A statistical model found that lapses in behavioral alertness were near-linearly related to the cumulative duration of wakefulness in excess of 15.84 hours (standard error 0.73). In other words, the cost starts to accumulate at around the length of a normal waking day.
Van Dongen HP, Maislin G, Mullington JM, et al. The cumulative cost of additional wakefulness: dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation. Sleep 2003. PMID 12683469
A comparison with alcohol puts a number on the first stage. In 39 subjects (30 transport employees and nine from the army) followed over 28 hours without sleep and then given alcohol up to about 0.1% blood alcohol concentration, performance after 17 to 19 hours awake (22:30 and 01:00 in the study) on some tests was equivalent to or worse than at 0.05%. Response speed was up to 50% slower on some tests, accuracy was significantly poorer, and after longer periods awake performance reached the level of the highest alcohol dose (0.1%).
Williamson AM, Feyer AM. Moderate sleep deprivation produces impairments in cognitive and motor performance equivalent to legally prescribed levels of alcohol intoxication. Occup Environ Med 2000. PMID 10984335
What happens if you stay up for 24 hours? Not sleeping 24 hours in detail
What happens if you stay up for 24 hours is better studied than any other duration. Not sleeping 24 hours is the typical all-nighter, and a meta-analysis of 70 articles with 147 cognitive tests on short-term (under 48 hours) total sleep deprivation found effect sizes from small and non-significant (reasoning accuracy, g = -0.125) to large (lapses in simple attention, g = -0.776). Time awake was the only moderator that predicted variation in the studies, and only for accuracy measures.
Lim J, Dinges DF. A meta-analysis of the impact of short-term sleep deprivation on cognitive variables. Psychol Bull 2010. PMID 20438143
A laboratory study in 36 people over two 12-day protocols supports the pattern: sleep loss mainly hit sleepiness and sustained attention, with much smaller effects on challenging working memory tasks, and the effects depended on the time of day.
Lo JC, Groeger JA, Santhi N, et al. Effects of partial and acute total sleep deprivation on performance across cognitive domains, individuals and circadian phase. PLoS One 2012. PMID 23029352
The body is affected too. In a PET study of 20 healthy adults, one night of sleep deprivation increased beta-amyloid burden in the right hippocampus and thalamus, and the increase was associated with worse mood. In 15 young physicians after one night on call, heart-rate variability showed a shift toward sympathetic activity and away from parasympathetic activity, and the inflammatory cytokine interferon-gamma increased, while hormone levels stayed unchanged.
Shokri-Kojori E, Wang GJ, Wiers CE, et al. β-Amyloid accumulation in the human brain after one night of sleep deprivation. Proc Natl Acad Sci U S A 2018. PMID 29632177
Tobaldini E, Cogliati C, Fiorelli EM, et al. One night on-call: sleep deprivation affects cardiac autonomic control and inflammation in physicians. Eur J Intern Med 2013. PMID 23601527
| Hours awake | What studies found | Source |
|---|---|---|
| About 16 | Lapses in alertness start to rise near-linearly beyond about 15.84 hours awake | Van Dongen et al. 2003, 48 adults |
| 17 to 19 | Some test results equal to or worse than at a blood alcohol level of 0.05% | Williamson and Feyer 2000, 39 subjects |
| 24 | Largest effect on lapses in attention; brain beta-amyloid up after one night; sympathetic shift in physicians | Lim and Dinges 2010; PET study of 20; 15 physicians |
| 24 to 48 | Perceptual distortions, anxiety, irritability, depersonalization, temporal disorientation begin | Waters et al. 2018, 21 studies |
| 48 to 90 | Complex hallucinations and disordered thinking | Same review |
| 72 and beyond | Delusions; the picture resembles acute psychosis or toxic delirium; many but not all symptoms resolved after normal sleep | Same review |
Is staying up for 24 hours bad, and is it bad to stay up all night?
Is staying up for 24 hours bad for you? The studies describe a short-term cost: slower reaction time, lapses in attention, worse mood, a stress response in the body, and a higher chance of an accident, especially on the road. The 28-hour experiment above concluded that the fatigue of sleep deprivation is an important factor likely to compromise safety on the road and in industry.
Is it bad to stay up all night once in a while? There is no evidence from these studies that a single night causes lasting harm in healthy adults, and the data on the beta-amyloid increase do not show lasting consequences. They do show that a single night is not neutral. A meta-analysis of 19 studies with 1,932 participants found that sleep deprivation strongly impairs human functioning, with mood affected more than cognitive or motor performance, and that partial sleep deprivation had a more profound effect than either short-term or long-term total deprivation.
Pilcher JJ, Huffcutt AI. Effects of sleep deprivation on performance: a meta-analysis. Sleep 1996. PMID 8776790
That last point is the most practical one. In the dose-response experiment, chronic restriction to 6 hours or less per night for 14 days produced deficits in cognitive performance equal to up to two nights of total sleep deprivation, and subjects were largely unaware of the growing deficit. Many people are therefore closer to the numbers in this article than they think, without ever pulling an all-nighter.
Not sleeping for 36 hours and staying up for 48 hours
Not sleeping for 36 hours has been studied mostly with brain imaging. In a study of 14 healthy volunteers, resting-state MRI after 36 hours of total sleep deprivation showed decreased functional connectivity of the thalamus with several cortical regions, which the authors read as a possible reason for the decline in arousal and information integration. After being awake 36 hours, people are also in the window where the 2018 review places the first perceptual distortions, irritability and anxiety (24 to 48 hours).
Shao Y, Wang L, Ye E, et al. Decreased thalamocortical functional connectivity after 36 hours of total sleep deprivation: evidence from resting state FMRI. PLoS One 2013. PMID 24205327
Staying up for 48 hours moves into the zone where the historical studies describe more than tiredness. Between 48 and 90 hours the review found complex hallucinations and disordered thinking, with visual changes the most consistent (in 90% of studies), followed by somatosensory (52%) and auditory (33%) ones. By the third day without sleep, hallucinations in all three modalities were reported. This is a description of what happened to volunteers in a few historical studies, not a goal.
How many days can you survive without sleep?
How many days can you survive without sleep, and how many days without sleep is too many? The scientific answer is that no human study has tested a limit and none will: the data stop at the 264-hour case. In the historical record, hallucinations and delusions developed progressively and in many cases resolved after a period of normal sleep, although not in all. Nothing in these studies supports a claim that a particular number of days is fatal, and nothing supports an attempt to find out. The rare diseases that do abolish sleep are conditions of the brain, not a matter of will, and are covered under fatal familial insomnia.
The risk that is certain is the accident. Drowsy driving, a microsleep at the wheel, a fall: those are what the safety literature worries about, long before any biological limit.
When tiredness is a medical question
If you cannot sleep even though you want to, for weeks, that is insomnia and not a choice; what is insomnia explains the definition. If you are very sleepy despite enough hours, or fall asleep at the wrong times, or snore and wake unrefreshed, a doctor can check for sleep apnea and other causes. Sleepiness while driving is a reason to stop and not continue.
What SleepTrace can show
SleepTrace does not measure alertness, performance or how long you have been awake, and it does not diagnose sleep disorders. It listens through the microphone of your iPhone or Android phone, sound only. After a short night you can see the sleep score and trends, with sleep phases estimated from sound, and compare a run of short nights with a run of longer ones. If you snore, the app stores playable clips with a dB peak and a time, and possible breathing pauses show up as timestamps without a clip. Its sleep apnea indicator is a screening estimate, not a diagnosis.
The free plan covers nightly tracking and 3 playable clips a month. Keep the app open (the screen dims by itself) and the phone on its charger. The app cannot tell you how impaired you are after a bad night, so it is not a tool for deciding whether you are fit to drive.
Frequently asked questions
There is no known limit, because studies beyond 48 hours are considered unethical today. The longest documented case is a 1966 report of a single person awake for 264 hours (11 days). Long before that, performance drops: after 17 to 19 hours without sleep some test results were equal to or worse than at a blood alcohol level of 0.05%.
Attention suffers most. A meta-analysis of 70 articles on short-term total sleep deprivation (under 48 hours) found the largest effect on lapses in simple attention (g = -0.776) and little effect on reasoning accuracy. After a single night awake, 20 healthy adults also showed higher beta-amyloid in the hippocampus and thalamus on PET scans, and mood worsened.
Nobody knows, and no study has tested it. The longest documented wakefulness in a person under observation was 264 hours. Hallucinations and delusions develop over the course of days awake and in many cases, though not all, resolved after normal sleep. Sleep deprivation is not a challenge: the risk before any limit is an accident, a car crash above all.
Once in a while it is a short-term cost rather than lasting damage: slower reaction, worse mood and attention for a day. In 15 young physicians studied after one night on call, sympathetic activity went up and an inflammatory marker (interferon-gamma) increased. Regular all-nighters and chronic short sleep are a different matter, because 6 hours a night for 14 days produced deficits equal to up to two nights without sleep.
In a dose-response experiment, lapses in alertness rose in a near-linear way with the time awake beyond about 15.84 hours. That is consistent with a normal day of roughly 16 hours awake and about 8 hours of sleep, though the right amount of sleep varies from person to person.
It lowers alertness enough to make driving or operating machinery risky, and the effects on mood and perception grow with time awake. After 36 hours of total sleep deprivation, an MRI study of 14 volunteers found reduced connectivity between the thalamus and several cortical areas. Anyone who is this tired should not drive.
SleepTrace is a wellness app, not a medical device. This article is general information, not medical advice. If your symptoms are frequent, severe or worrying, please talk to a doctor.
Worry about missing sleep tends to peak at three in the morning. SleepTrace records sound only and shows how long you actually slept, how broken the nights were and what the trend looks like, plus a timestamp for possible breathing pauses if you snore. It does not measure alertness or diagnose anything; constant exhaustion belongs with a doctor.
Hear your own night. SleepTrace turns a night of audio into your sleep phases, the sounds you made, and how it all trends. Works without a wearable, better with one. Your phone on the nightstand is enough to start. Get it for iPhone or Android →