Why Do I Feel Tired When I Wake Up In The Morning? | Sleep Inertia

Do you ever wake up feeling tired? Are you groggy and slow in the morning? Are you surprised you feel tired after an entire night’s sleep?

These are normal feelings most people experience. It can be difficult to start our day feeling worse than before. But there’s an actual reason behind this morning grogginess. And understanding the physiology behind this is key to understanding everything about our sleep cycle.

So today I will explain why we feel tired when we wake up in the morning.

What Is Sleep Inertia?

There is a scientific term for our morning grogginess: sleep inertia.

According to Dr. Lynn Marie Trotti, sleep inertia “refers to the transitional state between sleep and wake, marked by impaired performance, reduced vigilance, and a desire to return to sleep.” Sleep inertia can last for a few minutes or several hours.

This experience is natural and usually harmless. And sleep inertia can be experienced after a night’s sleep or an afternoon nap. In fact, afternoon naps lasting more than 30 minutes are notorious for inducing severe (but temporary) sleep inertia.

Additionally, sleep inertia is so common that one study considers it the third process of sleep regulation. I previously discussed what controls sleep in this article here. But now let’s add to our prior knowledge:

Sleep-wake homeostasis is the process that keeps track of our desire to sleep. This process also tells our body how intense our desire to sleep is. The longer we go without sleep, the stronger our desire to sleep.

Circadian rhythm is our body’s internal clock which regulates our sleep cycle. This process is controlled by the light-dark cycle of the world around us. When it’s light outside, we usually feel awake. And when it’s dark outside, we usually feel sleepy.

Sleep inertia occurs when we wake up during the transition between sleep and wakefulness. Since it is so commonly experienced, and our drive to return to sleep is so strong, this study concludes that sleep inertia is an integral part of our body’s sleep regulation.

Why Do I Experience Sleep Inertia?

Even though we mostly understand the concept of sleep inertia, its function is still a mystery. If we consider it from an evolutionary standpoint, sleep inertia is not beneficial. Imagine suddenly waking up to a threat you have to address immediately, but you wake up groggy and disoriented. Your chances of survival are now lessened.

Despite its functional mystery, we do understand why it happens.

Our brain needs a more gradual transition to wakefulness than our body. Immediately when we wake up, our brain is still emitting slower brainwaves. This means our brain is still in a sleep-like state even though our eyes are open and we are technically awake. Additionally, you may experience temporary paralysis related to sleep, which is also common when waking up.

Sleep inertia, and its intensity, may be controlled by which stage of sleep we wake up from. This is not definitively agreed upon in the scientific community, but its seems to be more accepted than not.

Some studies have suggested that waking up during REM sleep creates the strongest sleep inertia. Similarly, waking up in the middle of deep sleep could create strong sleep inertia.

We ideally want to wake up during stage 1 (N1) sleep, when our body has transitioned out of sleep and is heading toward wakefulness. This often happens when we wake up naturally, and we hopefully experience little-to-no sleep inertia. But, especially during the work week, we often wake up to an alarm that doesn’t care which stage of sleep we are in.

What Are the Side Effects of Sleep Inertia?

We’ve all experienced the side effects of sleep inertia. And we know how much they can impact the start of our day. We often group these side effects into the term “groggy,” but let’s explore the side effects specifically:

Disorientation is a common sleep inertia side effect. This usually presents itself as being briefly unsure of our surroundings. I personally feel disoriented after taking a nap, but it can happen in the morning, too. And it’s common to feel disoriented waking up in a new environment, whether that be a new home, a friend’s house, or a hotel.

Along with disorientation, confusion is very common. We may be confused by our location, but we may be confused by speech as well. It can be difficult for us to process spoken language immediately after waking up. If you’ve ever experienced someone saying something to you just after you wake up and you have no idea what they just said, this is due to sleep inertia.

Both of these side effects are part of sleep inertia’s biggest side effect: reduced cognition. When we wake up but our brain is still in a sleep-like state, our brain’s ability to process information is severely diminished. Many studies have shown that our memory is limited during sleep inertia. Other studies have shown that participants’ ability to correctly solve simple addition problems are lessened.

Finally, sleep inertia is often accompanied with reduced motor skills. We often wake up in a state of temporary sleep paralysis. This is a factor in driving our desire to remain in bed and go back to sleep. Once we get out of bed, our balance is often impaired. It’s common to stumble or trip while experiencing the effects of sleep inertia. Additionally, you may be more clumsy than usual first thing in the morning due to sleep inertia.

Can I Prevent Sleep Inertia?

It’s likely not possible to completely eliminate ever experiencing sleep inertia. But there are some things we can do to reduce its chances.

First, maintain a healthy sleep schedule. Be sure to get the recommended 7-9 hours of sleep a night, and try to keep your bedtime as consistent as possible.

Next, keep a great sleep environment. Your bedroom should be dark and not allow light to come in until morning. Your bedroom should also be quiet and free from distractions. These distractions also include electronics, like your phone or a TV. And don’t bring anything work-related into your bedroom.

Also, try to limit your caffeine consumption. This is something I talk about a lot, but caffeine can really interfere with your sleep. Caffeine can have lasting effects on your ability to sleep, especially if you consume caffeine late in the day.

Finally, try waking up naturally without an alarm clock. Now, obviously, don’t let yourself be late to work or school. But since an alarm doesn’t care which stage of sleep we’re in, it’s very possible to be woken in the middle of deep sleep. I just learned there are some alarms which wake you up based on sleep stages, and these are worth investigating.


Understanding the science behind waking up tired allows us to better understand what is happening to our body. When we know what our body is going through, we can make informed changes to our sleep routine.

I personally am very curious about these sleep stage alarms, and will hopefully be able to test one out. This could be a great experiment which could greatly benefit all of us.


Disclaimer: The content of the Calm Insomniac website is available solely for informational and entertainment purposes.  The creators of Calm Insomniac do not make any representation or warranties with respect to the accuracy, applicability, fitness, or completeness of its content.  The creators of Calm Insomniac are not medical professionals, and this content is not intended to be a substitute for professional medical advice, diagnosis, or treatment.  Any suggestions from these videos taken by you is assumed at your own risk.  Always seek the advice of your physician or other qualified health provider with any questions regarding your health.  To the extent permitted by mandatory law, the creators of Calm Insomniac shall not be liable to any party for any direct, indirect, implied, punitive, special, incidental, or other consequential damages arising directly or indirectly from any use of this content, which is provided as is, and without warranties.

Leave a Comment

Your email address will not be published. Required fields are marked *