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Is 4 Hours Sleep Enough? It’s Unlikely, Even if You Feel OK

Four hours of sleep is highly unlikely to be enough, even if you feel fine. The RISE app can tell you how much sleep you really need.
Written by
Jeff Kahn, M.S., Rise Science Co-Founder
Reviewed by
Chester Wu, MD, Rise Science Medical Reviewer
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We bring sleep research out of the lab and into your life. Every post begins with peer-reviewed studies — not third-party sources — to make sure we only share advice that can be defended to a room full of sleep scientists.
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Updated Regularly
We regularly update our articles to explain the latest research and shifts in scientific consensus in a simple and actionable way.

Is 4 Hours of Sleep Enough?  

  • Four hours of sleep is very unlikely to be enough sleep.
  • Most of us need about eight hours of sleep. The exact amount varies from person to person. 
  • Use the RISE app to find out how much sleep you need. If you struggle to get more than four hours, follow RISE’s personalized sleep hygiene recommendations that’ll help you fall and stay asleep easier each night.

Let’s get straight to the point: four hours of sleep isn’t enough for the vast majority of us. 

Even if you feel fine on four hours, your energy levels, productivity, and mental and physical health are probably impaired. 

Below, we’ll cover what happens when you get four hours of sleep, how much sleep you need instead, and how you can use the RISE app to get more sleep if you find yourself only managing a measly four hours a night.

Advice From a Sleep Doctor

Advice From a Sleep Doctor

Here’s what Rise Science sleep advisor and medical reviewer, Dr. Chester Wu, who is double board-certified in psychiatry and sleep medicine has to say:

“There’s only a very small percentage of people that can thrive on four hours of sleep. Four hours isn’t enough sleep for most of us. A lack of sleep can lead to low energy and poor focus the next day, and chronic sleep deprivation can lead to everything from heart disease to obesity, so you don’t want to make four hours a habit.”

Is Four Hours of Sleep Enough?

Four hours of sleep isn’t enough for most adults; most of us need much more than four hours of sleep to maintain cognitive function, emotional well-being, and overall physical health. Amongst our RISE users, the median sleep need is eight hours.

The amount of sleep you need is known as your sleep need. This number is unique to you and determined by genetics. 

We looked at the sleep needs of 1.95 million RISE users aged 24 and up and found it ranged from five hours to 11 hours 30 minutes. You can see how few people need five hours — let alone four hours of sleep. We found 48% need eight hours or more sleep a night. 

The RISE app can tell you how much sleep you need.
How much sleep RISE users need.

Other sleep need research shows there are a few lucky people who can get by on four hours of sleep. 

They may have what’s known as short sleep syndrome, which is caused by a gene mutation that allows them to sleep for about four to six hours without their well-being or performance taking a hit.  

These natural short sleepers are incredibly rare, and even if you have one of the mutations, you’re still not guaranteed to be able to get by on four hours of sleep. 

You can learn how much sleep you need here. 

Heads-up: You can’t really time your sleep to your sleep cycles or otherwise hack your way into making four hours of sleep work if you need more. 

Learn more about why it isn’t possible to sleep eight hours in four hours here.

And if you’re trying biphasic sleep (splitting your sleep into two chunks), be aware that this can lead to insufficient sleep and sleep experts agree that most of your nightly sleep should happen in one continuous chunk for better health and well-being. 

There are only two times when four hours of sleep is enough: 

  1. When you genetically only need four hours (unfortunately, very rare). 
  2. When a sleep specialist or clinically-backed insomnia app is guiding you through very temporary sleep restriction to help with insomnia. Don’t attempt this solo. Reach out to a doctor for advice and supervision. 

Dr. Jamie Zeitzer, Co-Director of the Center for Sleep and Circadian Sciences at Stanford University and one of our sleep advisors, sums it up: 

“For the vast majority of people, four hours of sleep isn’t enough. It’s not fatal in the short term, but you will definitely be impairing your daytime performance and health.” 

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What Happens if You Only Sleep Four Hours a Night?

There are many negative health effects of sleeping for four hours (or any amount that’s less than what you need). You may be able to survive on four hours of sleep, but you probably won’t be even close to thriving. 

In the short term, sleeping for four hours can lead to:

In the long term, sleeping for four hours can lead to: 

  • High blood pressure
  • Weight gain and obesity 
  • Diabetes 
  • Cardiovascular disease 
  • Poor mental health (including anxiety and depression) 
  • Multiple serious health conditions (a 2022 study found sleeping for five hours or less a night at ages 50, 60, and 70 increased the risk of having two or more chronic diseases like cancer and heart disease)
  • Early death

Heads-up: Sleeping for four hours disproportionately affects how much time you spend in each sleep stage across the night. We spend more time in deep sleep at the start of the night and more time in REM in the second half. Research shows people getting four hours of sleep spend less time in light sleep and REM, but the same amount in deep sleep compared to an eight-hour night. 

REM sleep is needed for creativity, emotional regulation, and memory consolidation.

When you get more sleep, you might experience REM rebound, when your body gets more REM to make up for what it missed out on. This could then affect your deep sleep. It’s not clear what happens if you chronically get four hours of sleep or the long-term impacts of messing with your sleep stages.

Is Four Hours of Sleep Enough Once a Week? 

Four hours of sleep isn’t enough once a week. Your energy, health, and performance will be hugely impaired. Even if you get enough sleep on other nights, one night of four hours can still leave you feeling tired, irritable, and unfocused the next day (and beyond if you don’t catch up).  

Is Four Hours of Sleep Enough for a Student?

Four hours of sleep isn’t enough for a student. Research shows getting four or six hours of sleep a night for two weeks has the same cognitive impairments as pulling two all-nighters. Too little sleep impacts your energy and health, too. Sleep need is fixed from young adulthood, but younger people often need more sleep, meaning it’s even more unlikely four hours will be enough for a student.

Why Do I Feel Fine on Four Hours of Sleep? 

There’s a slim chance you only need four hours of sleep. Even if you feel fine, you’re probably not doing as well as you think.

Your body produces more cortisol and adrenaline to keep you going on little sleep and your brain’s reward system fires up, so you feel more positive. 

You can also subjectively adapt to some feelings of sleep deprivation. Research shows we might not notice the increasing objectively measurable declines in cognitive performance we get from sleep loss. 

Plus, you might think yourself into feeling fine. A 2021 study found how people feel about their sleep impacted fatigue more than sleep duration. And a 2014 study found people performed better when they were told they’d had good-quality sleep.

There’s also your circadian rhythm, or body clock, to think about. This causes your energy to naturally fluctuate across the day. When you experience peaks in energy, you may feel like four hours of sleep is enough for you. But really, these peaks could be much higher if you got more sleep. RISE predicts the timing of your circadian rhythm each day, so you can see when these peaks and dips in energy will be. 

Additionally, you might attribute symptoms of sleep deprivation to stress or poor diet, and your caffeine habit might be masking some of the sleepiness. 

Learn more about why you feel energized on less sleep here. 

Expert tip: Check RISE to see how much sleep debt you have. This is the amount of sleep you owe your body. We recommend keeping this below five hours to feel and function your best. 

The RISE app can tell you how much sleep debt you have.

RISE users on iOS 1.202 and above can view their sleep debt here.

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What’s the Recommended Amount of Sleep? 

Here’s what the National Sleep Foundation says are the recommended amounts of sleep by age group: 

  • Newborns: 14 to 17 hours 
  • Infants: 12 to 15 hours 
  • Toddlers: 11 to 14 hours 
  • Preschoolers: 10 to 13 hours 
  • School-aged children: 9 to 11 hours 
  • Teenagers: 8 to 10 hours 
  • Adults: 7 to 9 hours 
  • Older adults: 7 to 8 hours 

Not a four hour recommendation in sight! 

But a word of warning: these guidelines are a good starting point, but they’re just guidelines. They’re based on how much sleep people get, not what they need, and on self-reported data, which can be inaccurate. 

For example, older adults may not need less sleep than adults, they just get less sleep.

As one paper puts it, “there is no “magic number” for the ideal duration of sleep.” 

Sleep affects everything important in life: energy, focus, health, mood. The list goes on. Don’t rely on generic guidelines or try to get by on a measly four hours. Instead, find out exactly how much sleep you need. 

You can do this by waking up without an alarm for a week or two and keeping track of your sleep times. You can get an idea of how much sleep you need when your sleep times regularize. This method is tricky to get right, however, as it’s hard to figure out when you fell asleep and, for most of us, it’s tough to find a week or two when we can wake up without an alarm. 

You can use the RISE app for an accurate way of finding how much sleep you need. RISE uses sleep science algorithms and a year’s worth of your phone use data to work out your sleep need down to the minute.

We’ve covered more on how to know if you’re getting enough sleep here.

RISE users on iOS 1.202 and above can view their sleep need here

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Why Can I Only Sleep for Four Hours?

You may only be able to sleep for four hours because: 

  • You’ve got poor sleep hygiene: If you’ve got poor sleep hygiene, you may struggle to fall asleep and wake up in the middle of the night on a regular basis. This includes sleeping in a warm bedroom, not winding down before bed, and drinking coffee too late in the day. You may wake up naturally after four hours as you switch to spending more time in REM, which is easier to be woken up from. Once you’re awake, poor sleep hygiene might stop you from getting back to sleep.
  • You’re out of sync with your circadian rhythm: You can get out of sync if you work night shifts, have jet lag, ignore your chronotype, or have an irregular sleep pattern. This can make it harder to fall and stay asleep as your body can’t predict when you’ll go to bed and wake up.
  • You’ve got a sleep disorder or medical condition: Health problems like sleep apnea, anxiety, IBS, or medications — just to name a few things — could be messing with your sleep. 
  • You only need four hours: Unfortunately, this is highly unlikely. Check RISE to see how much sleep you need. 

How to Get More Sleep? 

Get more sleep by improving your sleep hygiene. 

Here’s what to do: 

  • Get out in sunlight first thing each morning
  • Dim the lights about 90 minutes before bed 
  • Avoid caffeine, alcohol, vigorous exercise, and large meals too close to bedtime 
  • Have a relaxing bedtime routine 
  • Make your bedroom cool, dark, and quiet 
  • Keep a regular sleep schedule 

Use RISE to make sleep hygiene even more effective. The app can send you personalized reminders letting you know the best time to do 20+ healthy sleep habits based on your body clock. 

RISE users say these habits help them sleep and be more productive. This means you won’t have to cut your sleep to four hours to get everything done. 

“I never imagined that what you do throughout the day has such a profound impact on your sleep quality AND the energy dip in the afternoon. I now sleep better than ever and feel so much more productive throughout the day. Thank you RISE!” Read the review

RISE app screenshot showing your sleep hygiene habit reminders
RISE can guide you through 20+ sleep hygiene habits.

RISE users on iOS 1.202 and above can set up their 20+ in-app habit notifications here

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How to Not Feel Tired After Four Hours of Sleep?

You can feel less tired after four hours of sleep by getting out in sunlight, taking a cold shower, and exercising to feel more awake. Check RISE for when you’ll feel most alert that day, so you can schedule your most important tasks for this time. 

Then, catch up on lost sleep by getting to bed early, sleeping in, or taking naps. 

Just to make it clear, we’re not advocating getting four hours of sleep! But we know that sometimes you’ll have an early flight, tight work deadline, or teething toddler. 

You can learn how to function on no sleep here (only do this when you have to). 

Expert tip: Do a HIIT session. A 2022 study found high-intensity interval training helps stop the reduction in myofibrillar muscle synthesis (key for maintaining muscle mass) that sleeping for four hours can cause. And a 2021 study found HIIT can counteract the reduced glucose tolerance and mitochondrial respiratory function (energy conversion in your cells) that comes with sleeping for four hours. And HIIT releases feel-good endorphins, too.

It’s not clear if this works long term, though. And be careful to avoid injury when working out on no sleep.  

PSA: Four Hours of Sleep Isn’t Enough 

If you need the extra hours in the day (who doesn’t?), it’s tempting to try and get by on fewer hours of sleep — especially if you feel rested after just four hours. 

But four hours of sleep isn’t enough for most adults. We all need a different amount of sleep, but it’ll most likely be much more than four hours. 

Use RISE to find out how much sleep you need. And if you can’t get more than four hours when you try, follow RISE’s 20+ sleep hygiene habit recommendations to get a good night’s sleep. 

RISE helps 80% of users get better sleep within five days!

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