How Long Can You Go Without Sleep?

Fact Checked Medically reviewed by Tanja Premru-Sršen


What’s the most you’ve gone without sleep? Twenty-four hours at most, we assume.

Sleep is as vital as food, water, and air to function and maintain our health. Without these necessities, a person is most likely to not survive more than a few days.

Nobody knows how long a person can survive without sleep. It is not long before the adverse effects of going without sleep start showing.

Most of us procrastinate on sleep to either work or watch our favorite shows.

Read on to find out why you should not be sacrificing your sleep and how to achieve better wakefulness. After all, roughly a third of our lifetime is reserved for sleep.

How Long Can You Actually Go Without Sleep?

In 1965, Randy Gardener set the world record for the longest recorded time without sleep of 11 days or 264.4 hours. As a result, there was a significant decline in his motivation, perception, concentration, and higher-level mental processes.

The most worrying effect was the complaint of memory loss which felt like “an early Alzheimer’s thing brought on by lack of sleep.” 

In his book Why We Sleep, Mathew Walker points out, “The recycling rate of a human being is around 16 hours. After 16 hours of being awake, the brain begins to fail.”

It means that after being awake from 6 a.m. to 10 p.m, a person is most likely to start experiencing cognitive impairment.

24-Hours Without Sleep

An all-nighter’s most noticeable side effect would be how lousy you feel the following day. For example, you will find yourself getting irritated at the slightest blunder.

Not only that, a full day without sleep causes the same cognitive impairment in a human being as having a blood alcohol level (BAC) of 0.10%, which is higher than the legal limit.

Research shows that a day without sleep impairs “molecular clearance from the human brain,” especially in the cortex. In the long term, sleep deprivation heightens your risk of neurodegenerative disorders such as Alzheimer’s Disease.

36-Hours Without Sleep

The adverse effects of sleep deprivation speed up after a person has been awake for 36 hours.

A study conducted in 1997 confirmed that you are likely to have a slower reaction time, a higher chance of microsleep, and a reduced attention span due to less sleep.

The Journal of Sleep also reports that sleep-deprived people exhibit an expressionless voice and reduced speech eloquence.

According to a recent study, one and half-day without sleep affects the body’s ability to retain heat and maintain normal blood pressure.

48-Hours Without Sleep

Brace yourself for the backlash if you’ve gone two whole days without sleep.

A person’s immune system drastically weakens after being awake for two whole days. The Journal of Sleep Research warns us that two whole days without sleep drop in natural killer cell count. These are immune cells with antiviral and anti-tumor properties.

A person is more susceptible to microsleeps which may compromise your safety as it does not bode well for day-to-day tasks such as driving.

Did you know even an hour less of sleep can hinder your driving skills? According to the AAA Foundation for Traffic Safety, up to one-fifth of all fatal car crashes involve a sleep-deprived driver.

One may even start hallucinating after being awake for two whole days. This is because we face a decline in stimulus detection, which inevitably results in cognitive impairment.

72-Hours Without Sleep

It is a significant cause of concern if you have made three whole days without some shut-eye.

A study involving 12 astronauts concluded that those who stayed awake for 72 hours struggled with a poor mood, a faster heart rate, and diminished information processing.

A study on animals indicated more significant oxidative stress, circadian misalignment neuroinflammation, and heightened anxiety.

Gradual Sleep Loss: As Bad As All-Nighters

Sleep deprivation is not just the product of missing a whole night’s sleep or staying awake for long periods. A person can be sleep deprived even by regularly shaving off just one hour of sleep.

What we might dismiss as little rest, sleep debt is critical. It can be difficult to comprehend because we adapt subjectively to sleep deprivation. It might make us not feel exhausted.

You might not know that your emotional, cognitive, and physiological functions have already taken a significant hit. A 2017 study found that it took nine days of recovery sleep for participants to recover from unrecognized sleep loss.

So, How Much Sleep Do We Need?

A popular belief is everyone needs eight hours of sleep to retain energy throughout the day. This statement, however, is not true as there is no one size fits all solution to how much sleep a person should get.

All of us have a genetically determined need for sleep which varies from person to person. Our sleep needs also change throughout our lifespan. For instance, you might need 10 hours of sleep, whereas your friend might need 7 hours of sleep. Indeed, sleep needs can vary from person to person, but in general, experts recommend that healthy adults get an average of 7 to 8 hours of night sleep.

To answer the question of how much sleep do we need is entirely subjective. The general recommendation is the difference between one sleep-wake cycle and a person’s individual sleep need. For example, if you sleep for 8 hours, you need to stay awake for 16 hours.

Acute vs. Chronic: The Two Levels Of Sleep Deprivation

Even if you are not pulling constant all-nighters, not meeting your sleep needs eventually leads to sleep deprivation.

Sleep deprivation falls into two categories: acute, short-term, and chronic, long-term.

Acute Sleep Debt

Acute Sleep Debt refers to the amount of sleep one has missed relative to your biological sleep need over the past 14 days.

One can rack up acute sleep debt by pulling an all-nighter or only sleeping six hours a night constantly when your body needs nine hours.

Prolonged Sleep Deprivation

Prolonged Sleep Deprivation or Chronic Sleep Deprivation is much more than just losing a good night’s sleep.

With this type of sleep debt, you are not regularly meeting your sleep needs, much less paying back any deficit.

The American Academy of Sleep defines chronic sleep debt as restricted sleep for three months or longer.

If a person has constantly been undersleeping for most of their life, for example, getting a shut eye for 6 hours instead of regular 8-hour sleep, they’re likely plagued with chronic sleep deficiency and acute sleep debt too.

What Are The Negative Effects Of Acute And Chronic Sleep Deprivation?

Sleep deprivation, both in the short and long term, makes one feel muddle-headed and bone-weary even before your day has started. You will find yourself excessively sleepy and yawning without any reason.

In some cases, one might not feel quite tired even after sleeping for less than they need. It is because the suprachiasmatic nucleus in your brain or circadian clock releases more cortisol, i.e., a stress hormone, making us feel more awake.

Unfortunately, higher levels of stress hormone take a toll on our mental health. It also slows down the rate at which our body recovers from stress. Below are some of the adverse effects of acute and chronic sleep deprivation.

Adverse Effects Of Acute Sleep Deprivation

According to the Journal of Nature and Science of Sleep, acute sleep loss causes:

  • Immediate changes to your metabolism rate as your body starts producing less leptin and more ghrelin. This, in turn, causes our appetite to increase.
  • Higher risk of severe daytime sleepiness
  • Poorer mental health – increased anxiety, depression, and stress.
  • Increase in negative emotions such as irritability and impatience.
  • Reduced cognition, difficulty in paying attention, decision making, judgment, and memory formation

Adverse Effects Of Chronic Sleep Deprivation

The psychological, emotional, and physiological repercussions of chronic sleep debt are labeled as a public health epidemic as they’re so harmful.

Research indicates “50 to 70 million Americans chronically suffer from a disorder of sleep and wakefulness.” 

The detrimental effects of prolonged sleep deficit are as follows:

  • Heightened chances of metabolic disorders such as Type-3 diabetes and obesity
  • Increased risk of cancers, for example, colorectal cancer and breast cancer
  • Increased BMI which is an indication of weight gain
  • Poor mental health with a close association with suicide

The Takeaway

Although it is interesting to probe the boundaries of sleeplessness, the near-term effects are functioning and feeling sub-optimal, and the long term is ultimately death.

In the end, one must remember that getting enough sleep is as vital as oxygen and food. If you wish to truly optimize your sleep schedule, your focus should be meeting your sleep needs.