The longest scientifically documented time a person has gone without sleep is 264 hours, or exactly 11 days. A 17-year-old San Diego high school student named Randy Gardner set that record in 1964 as a science fair project, staying awake under constant medical supervision. While an unofficial claim of over 18 days exists, Guinness World Records no longer tracks this category because of the serious health risks involved.
Randy Gardner’s 11-Day Record
In December 1964, Randy Gardner decided to break the existing sleep deprivation record for a school science fair project. He was monitored by Dr. John Ross for most of the attempt and by Dr. William Dement, one of the leading sleep researchers at the time, for the final three days. Dement kept Gardner occupied with activities like late-night basketball games and trips to the arcade to help him stay awake without stimulants. Gardner used no caffeine or drugs of any kind during the attempt.
By the end of the 264 hours, Gardner was still technically functional. He held a press conference and spoke without slurring his words. But the days leading up to that point told a different story. He became increasingly irritable, paranoid, and disoriented. He struggled to focus, lost short-term memory, and experienced hallucinations. When he finally went to sleep, he slept for about 14 hours, then returned to a roughly normal sleep schedule within days.
What seemed like a full recovery wasn’t. Decades later, Gardner told NPR that the teenage stunt “came back to haunt him.” He developed severe, unbearable insomnia that lasted years. He described himself as awful to be around, easily upset, as if the effects of what he did 50 years earlier had never fully gone away. He eventually regained the ability to sleep, but only about six hours a night. “Randy Gardner, the man who conquered sleep, is now terrified of going a night without it,” NPR reported in 2017.
The Unofficial Claim: 18 Days
In 1986, Robert McDonald reportedly stayed awake for 453 hours and 40 minutes, just under 19 days. That figure comes up in sleep science discussions, but it lacks the rigorous medical documentation that Gardner’s record had. There’s no published clinical data detailing McDonald’s cognitive state, vital signs, or verification methods throughout the attempt.
It was partly in response to McDonald’s attempt that Guinness World Records decided to stop accepting new entries for sleep deprivation. The organization cited safety concerns and has not reinstated the category. In 2007, a British man named Tony Wright claimed 266 hours of continuous wakefulness (just over 11 days), narrowly surpassing Gardner’s time. Wright attributed his endurance to a raw food diet of carrot juice, bananas, avocados, pineapple, and nuts. But without official Guinness recognition or published medical monitoring data, these later claims remain unverified in any formal sense.
What Happens to Your Body and Brain
Sleep deprivation follows a surprisingly predictable pattern. The first 24 hours feel roughly like being drunk: slower reaction times, impaired judgment, difficulty concentrating. Most people have experienced some version of this after a long night.
At 48 hours, the brain starts taking “microsleeps,” brief episodes lasting a few seconds where you lose awareness entirely, even with your eyes open. You can’t prevent them through willpower. Mood deteriorates sharply, and simple tasks become difficult to complete.
By 72 hours, the effects resemble psychosis. People at this stage commonly see, hear, and feel things that aren’t there. They may hold beliefs that don’t match reality and display intense, unpredictable emotions. This isn’t a dramatic exaggeration. It’s a well-documented neurological response to the brain being denied its basic maintenance cycle.
Beyond 72 hours, the data gets thinner because so few people have been monitored at these extremes. Gardner’s observers noted that his symptoms worsened in waves rather than on a straight line. He would seem somewhat lucid, then rapidly deteriorate. The hallucinations became more elaborate, and his ability to perform basic cognitive tests dropped significantly before partially rebounding as his body fought to compensate.
Can Sleep Deprivation Kill You?
No healthy human has died from voluntarily staying awake, at least not under documented conditions. But there is strong evidence that forced, total sleep deprivation is fatal. In well-known laboratory experiments, rats kept awake continuously died within two to three weeks. They developed a cascade of problems: their body temperature regulation failed, they ate more but lost weight rapidly, and their metabolic systems broke down. The cause of death appeared to be linked to the body losing its ability to regulate temperature and energy.
In humans, a rare genetic condition called Fatal Familial Insomnia offers the closest parallel. This prion disease progressively destroys the brain’s ability to initiate sleep. Patients experience worsening insomnia that eventually becomes total, along with cognitive decline, hallucinations, and organ failure. Survival from symptom onset ranges from 7 to 73 months, though the disease involves widespread brain degeneration beyond just sleep loss.
Why the Record Will Likely Stand
Gardner’s 264-hour record remains the most credible benchmark because of the medical documentation surrounding it. With Guinness refusing to track the category, there’s no institutional framework for verifying new attempts. Researchers have no interest in supervising them either. The scientific community learned what it needed from Gardner and a handful of similar experiments in the 1960s: sleep deprivation is profoundly dangerous, the cognitive effects are severe and rapid, and the long-term consequences can persist for a lifetime.
Gardner himself, now in his late 70s, has been clear about one thing. He wishes he’d never done it.