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Sleep Inertia: A Sleep Expert Explains How to Fix Grogginess

Sleep inertia is the groggy feeling you get after waking up. You can reduce it by drinking coffee, getting out in natural light, and doing a burst of exercise.
Written by
Jeff Kahn, M.S., Rise Science Co-Founder
Reviewed by
Chester Wu, MD, Rise Science Medical Reviewer
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Sleep Inertia: Why You Feel Groggy and How to Manage It

  • Sleep inertia is the groggy feeling you get when you wake up in the morning or from a nap. It’s not clear what causes sleep inertia exactly. One theory is that it’s caused in part by a chemical in your brain called adenosine.
  • You can reduce sleep inertia by drinking coffee, doing a burst of exercise, playing your favorite music, or getting out in sunlight. 
  • The RISE app can predict how long your sleep inertia will last each morning and help you get more morning energy by lowering your sleep debt and syncing up with your circadian rhythm.

Your alarm goes off and you feel like death. Sound familiar? If so, you’ve got sleep inertia. 

But don’t worry, most of us do. Sleep inertia is the grogginess you feel when you wake up and it’s completely natural. 

Luckily, there are ways you can reduce sleep inertia and shake it off faster. 

Below, we’ll dive into what sleep inertia is, what causes it, and how you can feel better after waking up — both in the morning and from a nap. We’ll also cover how you can use the RISE app to see how long sleep inertia is expected to last for you each morning based on your own biology and how you can build a morning routine to manage it. 

Here's What a Sleep Doctor Says

Here's What a Sleep Doctor Says

Dr. Chester Wu is double board certified in psychiatry and sleep medicine. He’s also our Rise Science sleep advisor and medical reviewer. Here’s his advice on battling sleep inertia.

“Sleep inertia is natural, but you can reduce how long it lasts. Do some exercise and get out in natural light to wake yourself up faster. The win-win here is that these activities can help you fall asleep later that night, too, and getting enough sleep can also reduce sleep inertia.”

What is Sleep Inertia? 

Sleep inertia is the temporary groggy feeling you get when you wake up. You may feel drowsy, disorientated, and like your brain and body are moving through sludge. 

This can last a few minutes or a few hours, and it can happen after a night of sleep and after a nap. 

Sleep inertia is natural and you’ll get it even if you’re getting enough sleep

The lowered performance from sleep inertia is no joke. A 2019 paper said the performance impairment from sleep inertia can be the same as or even worse than 40 hours of sleep deprivation. 

Scientists aren’t sure why sleep inertia happens, but it’s thought a gradual awakening could be a protective mechanism to help you fall back to sleep if you wake up during the night.

What Are the Symptoms of Sleep Inertia? 

The symptoms of sleep inertia include: 

  • Sleepiness or grogginess 
  • A desire to fall back asleep 
  • Disorientation or brain fog
  • Impaired cognition 
  • Impaired decision-making skills 
  • Reduced reaction times 
  • Lower mood 

Severe sleep inertia is known as sleep drunkenness. This can cause:

  • Confusion
  • Slowness
  • Lack of coordination
  • Going back to sleep  

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How Long Does Sleep Inertia Last?

Sleep inertia can last from one minute to four hours. But everyone’s different — you may shake off sleep inertia in a matter of minutes or spend several hours each morning feeling like you’ve been beaten up.

RISE can tell you how long your sleep inertia will last each morning based on your biology.

In the largest real-world study of its kind — co-authored by our advisor Dr. Jamie Zeitzer, Co-Director of the Center for Sleep & Circadian Sciences at Stanford University — researchers found people’s cognitive performance (measured through the speed of keystrokes and click interactions on a search engine) was lower during the first two hours after waking. 

"I think this is the first real-world measure of how long it takes people to wake up," Dr. Zeitzer told the Stanford Medicine Scope Blog. Once participants had shaken off sleep inertia, performance was at its best and then gradually declined until they’d been awake for about 16 hours — which is usually when people start heading to bed.

There are several factors that can affect the duration of sleep inertia or make it feel worse, including: 

  • Sleep debt: Sleep debt is the amount of sleep you owe your body. If you’ve got a lot of sleep debt or you’ve been awake for a long time before sleeping, sleep inertia will feel worse and last longer. 
  • Waking up during deep sleep: Results are mixed, but there’s some evidence suggesting you’ll feel more groggy if you wake up during the slow wave sleep, or deep sleep, phase of your sleep cycle compared to other stages of sleep, like light sleep and rapid-eye-movement sleep (REM sleep). More recent literature suggests sleep deprivation may, in fact, play a mediating role in whether or not waking up in deep sleep affects how much sleep inertia you have and how long it lasts. 
  • Recovery sleep: If you’ve got sleep debt, you might take the chance to catch up on sleep when you can. This recovery sleep can make sleep inertia feel worse — although rest assured, recovering from prior sleep loss is a good thing in the long run.
  • Chronotype: Your chronotype is whether you’re an early bird, night owl, or something in between. This dictates your natural tendency towards earlier or later wake times and sleep times. Night owls may need more time to wake up in the morning. Research shows performance improves within 10 to 20 minutes of waking for morning people, but it takes more than 30 minutes for night owls.  
  • Waking up during the night: You may feel even more groggy and confused if you wake up and try to be “on” during the night. You might feel this if you do shift work, for example.  
  • Sleep disorders, health conditions, and mental health issues: These could make sleep inertia feel worse and last longer, especially if they disrupt your sleep. Conditions that make it feel like you can’t wake up include anxiety, ADHD, obesity, hypersomnia, and sleep apnea
  • How much exercise you did the day before: Research from 2022 shows the more physical activity you do, the more awake you’ll feel the next morning.  
  • What you eat for breakfast: Yes, a coffee will perk you up, but what you eat makes a difference, too. The same 2022 research found a breakfast rich in carbs that are slowly digested and absorbed (think oatmeal or whole wheat bread) is linked to more morning alertness. A lower blood glucose response following breakfast is also linked to more alertness. 
  • How long you nap for: Shorter naps are less likely to cause sleep inertia. One study found short naps of five to 20 minutes didn’t cause sleep inertia, but a 30-minute nap did. You might feel sleep inertia for 15 to 30 minutes after a long nap.

Heads-up: Sleep debt is measured against your sleep need — which is the name for the amount of sleep you need each night. This is determined by genetics and it can vary quite a lot from person to person.

For example, when we looked at how much sleep 1.95 million RISE users aged 24 and up need, we found sleep needs ranged from a tiny five hours to a whopping 11 hours 30 minutes.  

RISE can work out how much sleep you need exactly, so you know what to aim for each night.

The RISE app works out how much sleep you need
The RISE app works out how much sleep you need.

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

What Causes Sleep Inertia? 

It’s not clear what causes sleep inertia exactly. One theory is that it’s caused in part by adenosine. 

Adenosine is a natural compound that builds up in your brain while you’re awake. As adenosine levels rise, it eventually makes you feel sleepy and causes sleep pressure, or the urge to sleep.  

While asleep, adenosine is purged from your system, resetting the balance for the next day. 

But when you wake up, there are still trace amounts of adenosine in your system — and this may be part of the reason you feel half asleep when you wake up.

Is Sleep Inertia Dangerous? 

Sleep inertia itself isn’t dangerous, but the grogginess and cognitive impairments can be, especially if you need to perform as soon as you wake up. 

For example, research shows decision-making skills are 51% lower during the first few minutes after awakening and 20% lower 30 minutes after waking up. Your reaction times can also be impaired. So it can be dangerous if you drive with sleep inertia

Sleep inertia can be dangerous at work too if, for example, you’re a shift worker snoozing during a night shift. When you wake up, you need your cognitive functions to be working well ASAP, but they may be lagging behind. This can be life-threatening (to either the person waking up or to others) for people such as military personnel, healthcare workers, firefighters, and pilots. 

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How to Get Rid of Grogginess in the Morning? 

You can’t fix sleep inertia altogether, but there are some countermeasures that can make it feel more manageable and last less time. 

Here’s how to get rid of sleep inertia faster when you wake up feeling groggy: 

1. Don’t Hit Snooze 

As tempting as it is when you wake up sleepy, don’t hit snooze on your alarm clock. 

A 2022 study found hitting snooze makes sleep inertia last longer compared to using a single alarm.

Instead, either get out of bed as soon as your alarm goes off — try putting your phone or alarm on the other side of the room — or set a later alarm and use the time you’d spend snoozing to get more unbroken sleep (which can reduce sleep inertia).

Headlines around a 2023 study claim that hitting snooze for 30 minutes can reduce sleep inertia and help you perform the same or better on cognitive tests. But these headlines can be misleading.

The study used self-reported data and was small — only 31 people. And more importantly, participants were sleep deprived and night owls. These groups often benefit from more sleep or a later wake-up time, so we can’t draw solid conclusions.

We’ve covered more on how to wake up to an alarm here.

2. Use a Gentler Alarm 

Abrupt awakenings aren’t a fun way to start the day. Instead of the shrill default alarm sound, choose a gentle alarm that slowly wakes you up. Try this tip for tomorrow morning. 

These alarm sounds may help you feel less sleep inertia when you wake up: 

Expert tip: Use the RISE alarm. You can choose from melodic sounds, your choice of music, or gentle vibrations on your phone or Apple Watch. When you turn off the alarm, RISE will kick you straight to your favorite app for 15 minutes of phone time to help you wake up slowly.

The RISE alarm also tells you as you’re setting it the night before whether your wake-up time will add to your sleep debt, which can make grogginess worse. 

RISE app screenshot showing the smart alarm feature
The RISE app can wake you up with a gentle alarm.

3. Get Out in Natural Light  

Getting light exposure first thing resets your circadian rhythm, or body clock, helping you feel alert during the day and sleepy at night. It suppresses your sleep hormone melatonin and triggers your alertness-boosting hormone cortisol. Real-world research from 2023 supports the connection between brighter light after waking up and reduced sleep inertia.

Aim to get 10 minutes of light as soon as you can each morning. If it’s overcast or you’re getting light through a window, stay in sunlight for 15 to 20 minutes. 

If it’s dark outside when you wake up, try using a 10,000 lux light therapy lamp. Place the lamp 16 to 24 inches from your face for 30 minutes. 

4. Do a Burst of Exercise 

A 2021 study asked participants to do a burst of high-intensity exercise, low-intensity exercise, or no exercise following a two-hour nap. 

Both types of exercise helped participants feel more awake, but high-intensity exercise was more effective. 

You don’t need to do a full workout to get the energy-boosting effects — this study was on only 30 seconds of exercise!

Expert tip: Plan a full workout beyond that morning burst of activity. Research from 2022 shows daytime exercise can help you feel more alert the next morning. 

5. Play Your Favorite Music 

Your favorite playlist can help you wake up faster.

One study found playing excitative music for 20 minutes after a nap can help reduce sleep inertia. It was even more effective when participants listened to music they liked.  

6. Drink Coffee 

Caffeine temporarily blocks adenosine receptors in your brain, making you feel more alert. 

A morning cup of coffee can be a great pick-me-up, just be sure to avoid it come the afternoon. A 2023 meta-analysis found caffeine can keep you up, wake you up in the night, and reduce your deep sleep.   

Caffeine can last in your system for more than 12 hours. Check RISE for when to have your final coffee each day. 

7. Do Easy Tasks First Thing 

This tip won’t necessarily reduce the effects of sleep inertia, but it will help you manage the grogginess better. 

When you feel groggy, don’t fight it and try to jump into work or a demanding workout. 

Do easy tasks in the early morning such as: 

  • Household chores
  • Going for a walk 
  • Writing your to-do list

Get more morning routine ideas here.

Anxiety around sleep inertia and feeling your best first thing can, ironically, make it worse as anxiety can keep you up at night and cause sleep loss. 

If you need to be “on” at a certain time, aim to be up about 90 minutes beforehand to give yourself enough time to shake off sleep inertia.

RISE predicts how long you’ll experience sleep inertia each day. You can then schedule your day to match.

RISE app screenshot showing your energy schedule
The RISE app can predict how long sleep inertia will last each morning.

8. Avoid Screens Before Bed 

A 2020 study found the more exposure you get to blue light from screens in the evening, the more sleep inertia you feel the next morning. 

Blue light can keep you awake, causing you to build up sleep debt and more morning grogginess. 

Don’t want to give up pre-bed screen time? We’ve covered how to use screens before bed here.

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How to Feel Less Groggy in the Morning Long Term? 

You might not be able to avoid sleep inertia in the morning altogether, but you can feel less groggy by getting enough sleep and syncing up with your circadian rhythm, or body clock. These are the two biggest factors influencing your energy levels, and getting the right can reduce sleep inertia in the long run. 

Lower Your Sleep Debt 

The higher your sleep debt, the more sleep inertia you’re going to feel. If you feel like sleep inertia lasts all day, you may be sleep deprived. 

We recommend you keep sleep debt below five hours to feel the most energy each day. 

You can lower your sleep debt by: 

  • Taking short afternoon naps 
  • Going to sleep a little earlier 
  • Sleeping in a little later 
  • Improving your sleep hygiene 

Heads-up: Sleep hygiene are the daily habits that can help you fall asleep faster and wake up less often, so you’ll get more sleep overall. Good sleep hygiene includes keeping a consistent sleep pattern, avoiding caffeine and alcohol close to bedtime, and making sure your bedroom is cool, dark, and quiet.

RISE can tell you how much sleep debt you have and when to do 20+ sleep hygiene habits at the ideal time for your body clock each day. 

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

Get in Sync With Your Circadian Rhythm 

Your circadian rhythm is your roughly 24-hour body clock that helps to control your sleep-wake cycle. 

You can get out of sync with your circadian rhythm if you:

  • Work night shifts
  • Have social jetlag — or an irregular sleep schedule, which about 87% of us do
  • Ignore your chronotype — like a night owl forcing themselves to wake up early

Being out of sync can cause low energy, both in the morning and throughout the day. It also increases your odds of waking up during deep sleep. 

Heads-up: You may feel groggier when you wake up during deep sleep, but you can’t really control which sleep stage you wake up in. Timing your alarm to go off at the end of a sleep cycle doesn’t really work and everyone’s sleep architecture (how sleep is structured into REM and non-REM stages) looks different.

The best thing you can do is go to sleep and wake up at similar times each day in a way that allows you to meet your sleep need. This will help you sync up with your circadian rhythm, get enough sleep, and reduce your chances of waking up during deep sleep.

New 2023 guidance from the National Sleep Foundation says a consistent sleep schedule is important for health, safety, and performance. Although catching up on sleep may be beneficial. 

RISE can predict the timing of your circadian rhythm each day, so you can see when your body naturally wants to go to sleep (look for your Melatonin Window) and wake up. 

RISE app screenshot showing your melatonin window
The RISE app can predict your circadian rhythm.


RISE users on iOS 1.202 and above can see their circadian rhythm on the Energy screen here

We’ve covered more ways to have more energy in the morning here. 

How to Get Rid of the Groggy Feeling After a Nap?

Many of the ways to get rid of morning sleep inertia can work to get rid of grogginess after a nap. 

You can reduce sleep inertia after a nap by: 

  • Doing a burst of exercise 
  • Taking a short nap (10 minutes may be best) 
  • Playing your favorite music
  • Getting out in bright light 

The more sleep debt you have and the longer you’ve been awake, the worse sleep inertia will feel and the longer it’ll last. If you’re really sleep deprived, you might even get sleep inertia after a short nap. 

Heads-up: Avoid drinking coffee after a nap if it’s too close to bedtime as this can make it harder to fall asleep at night.

What’s the Best Nap Length to Avoid Sleep Inertia? 

In general, the shorter your nap, the less likely you are to feel sleep inertia when you wake up. 

One study looked at participants who took a five, 10, 20, or 30-minute nap — or no nap at all — after a night of sleep deprivation. 

The five-minute nap wasn’t long enough to produce any benefits. 

The 10-minute nap led to immediate improvements in sleepiness, vigor, and cognitive performance, with some benefits lasting for more than two and a half hours. 

The 20-minute nap also led to improvements, but these didn’t last as long or happen as quickly. 

And the 30-minute nap led to similar benefits as the 10-minute nap, but it came with sleep inertia.  

We’ve covered more on the best nap length here.

Expert tip: Check RISE for the best time of day to take a nap — aim for your afternoon dip in energy. You don’t want to nap too close to bedtime as this can make it harder to fall asleep at night. 

The RISE App Can Predict and Reduce Your Sleep Inertia 

If you feel like death in the morning, you’re probably experiencing sleep inertia. RISE can predict how long your morning grogginess will last, so you can plan for it. 

RISE can also help you lower your sleep debt, get better sleep with sleep hygiene, and get in sync with your circadian rhythm to feel more energy in the morning. 

Don’t just take our word for it. RISE users agree: 

  • “It is helping me to realize that it’s normal to feel groggy upon waking, that an afternoon dip will occur, and I can aim to get to bed at the most opportune time to fall asleep.” Read the review
  • “Being able to visually map out my grogginess and see how my sleep debt has been affecting my energy levels has made all the difference.” Read the review
  • “RISE helps me to accurately track things like my nightly Melatonin Window, my predicted energy peaks and dips throughout the day, and my “Wake Zone” a.k.a. the best time for me to wake up in order to feel refreshed in the morning.” Read the review

Plus, 80% of RISE users feel more morning energy within five days.

Summary FAQs

What is sleep inertia?

Sleep inertia is characterized by a temporary period of sleepiness and poor cognitive performance from the moment you wake up. It can cause grogginess, slowed reaction times, disorientation, and impaired decision-making skills. Sleep inertia can last a few minutes to a couple of hours. But everyone’s different, and there are several factors that can affect the duration of sleep inertia or make it feel worse, including how sleep deprived you are, your chronotype, and whether you keep a consistent sleep schedule.

Is sleep inertia normal?

Sleep inertia is normal and very common. Most of us feel groggy after a sleep period, including when we first wake up or after a nap. This can happen even when we’ve had enough sleep.

What does sleep inertia feel like?

Sleep inertia feels different for everyone but common symptoms include grogginess, disorientation, low mood, slowed reaction times, and impaired decision-making skills.

What causes sleep inertia?

It’s not clear what causes sleep inertia. One theory is that sleep inertia is caused in part by adenosine. This is a chemical that builds up in your brain while you’re awake, eventually making you feel sleepy. Adenosine is purged from your system as you sleep, resetting the cycle. But trace amounts can still be found when you wake up — making you feel groggy.

How do I get rid of sleep inertia?

Get rid of sleep inertia by not hitting snooze, using a gentle alarm, getting out in natural light, drinking coffee, doing a burst of exercise, and playing your favorite music. Keeping your sleep debt low and staying in sync with your circadian rhythm will help you feel more energy each morning.

How long is sleep inertia on average?

On average, sleep inertia can last a few minutes to a couple of hours. Some people may be able to shake grogginess off in a matter of minutes, but others can feel groggy and slow for four hours.

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Sleep Inertia

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