Why Am I Still Tired After 8 Hours of Sleep: 3 Likely Culprits

Why am I still tired after 8 hours of sleep? Blame it on a sleep need that exceeds eight hours, poor sleep efficiency, and/or pre-existing sleep debt.
Written by
Jeff Kahn, M.S., Rise Science Co-Founder
Reviewed by
Jamie Zeitzer, PhD, Rise Science Scientific Reviewer
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Man waking up in the morning but still tired

For some people, prying your eyelids open after eight solid hours of sleep can feel like a Herculean effort. Even though you’ve had what seems like a good night’s sleep, you struggle to wake up when your alarm clock rings. Aside from the usual sleep inertia (translation: wake-up grogginess), why am I still tired after 8 hours of sleep?

Because this daily scenario runs counter to oft-repeated guidelines from national health organizations like the Centers for Disease Control and Prevention, doubts begin to creep into your mind. Are you the victim of some undiagnosed medical condition, say, iron deficiency anemia or obstructive sleep apnea? Or maybe the ever-present grogginess is a risk factor for chronic illnesses like heart disease.

Before you scare yourself silly, we’ll share with you three non-medical reasons why you’re still tired after eight hours of sleep.

Disclaimer: This post is not intended as medical advice. While the RISE app supports natural sleep patterns and boosts sleep hygiene, it does not treat medical conditions.

Why Am I Still Tired After 8 Hours of Sleep?

The good news is, it’s not the health scare you catastrophize in your mind. Instead, blame the lingering drowsiness on misinformation, inefficiency, and debt (of the sleep variety, that is).

Your Sleep Need Is More Than 8 Hours

We’re often told to get eight hours of sleep per night if we want to be in top form the next day. But did you know your sleep need is genetically determined and thus unique to you? In other words, if you’re always so tired even after 8 hours of sleep, there’s a high chance your individual sleep need is more than the recommended eight — and definitely more than the scanty few hours of sleep the hustle culture propagandize. 

To quote Dr. Thomas Roth in Matthew Walker’s book, Why We Sleep, “The number of people who can survive on 5 hours of sleep or less without any impairment, expressed as a percent of the population, and rounded to a whole number, is zero.”

And science has the statistics to back it up.

A 2016 study found the average sleep need stands at 8 hours and 10 minutes per night (plus or minus 44 minutes or so). That means your sleep need could very well be closer to nine hours than the expected eight. For 13.5% of the general population (a not-so-insignificant percentage, they need a longer sleep schedule of nine hours or more every night.

If you undersleep your sleep need, not only do you feel tired the next day, but you will also perform poorly across all the parameters that matter — think cognition, emotion, and physiology.

You Overestimate Your Actual Sleep Time in Bed

Repeat after us: Time spent in bed does not equal time spent asleep. Between sleep latency (you take some time to fall asleep) and sleep fragmentation (you wake up at least once during the night), your sleep efficiency isn’t at 100%.

To better understand sleep efficiency, we’ll use a hypothetical example:

Your bedtime begins at 10 p.m., and your alarm clock is set to ring at 6 a.m., so you could get eight hours of sleep, theoretically speaking. In reality, though, you likely don’t immediately snooze when you slide between the sheets. Perhaps you spend about 30 minutes scrolling on your phone or watching Netflix. Then, it takes you roughly another 30 minutes of tossing and turning before you finally fall into a deep sleep.

Still, you’re not guaranteed uninterrupted sleep from here on till morning. Maybe the urge to use the facilities or an abrupt awakening from a nightmare have you waking up in the middle of the night. A sleep environment that’s too noisy, bright, or hot could also be blamed for your sleep problems. Not to mention, unhealthy sleep habits such as too-late caffeine consumption and large evening meals often throw a wrench into your sleep schedule.

You may not even remember many of the shorter (<10 minute) awakenings that happen in everyone every night. This process (“retrograde amnesia”) is also why you don’t remember the minutes before falling asleep at the beginning of the night.

Accounting for the time it takes you to fall asleep as well as middle-of-the-night awakenings, remembered or otherwise, it’s safe to say that you’ve had significantly less sleep than the expected eight hours. Perhaps you’ve only managed six hours of total sleep time, rating your sleep efficiency at around 75%. (For the record, you’ll want to aim for a sleep efficiency of 85% or more.) Add on to the fact that your sleep need is likely more than eight hours, the resulting lack of sleep is the reason why you’re still tired all the time.

You’re Already Burdened With Sleep Debt

RISE app screenshot showing your sleep debt progress
The RISE app shows the amount of sleep debt you've accumulated per night across the past 14 nights on your Progress screen.

Perhaps you can unequivocally state that in sleeping 8 hours you met your sleep need last night. But you still feel like you need multiple naps throughout the day despite getting “enough sleep.” One likely reason for this is that you’re already carrying sleep debt from previous nights.

Let’s imagine that your individual sleep need is indeed eight hours. If you’ve slept eight hours last night but averaged 6-7 hours in the past week, clearly, you’ve fallen short of your biological sleep requirements.

Contrary to popular misconception, sleep debt isn’t just based on last night’s missed sleep. Instead, it’s inclusive of all the z's you’ve skipped out on in the past 14 nights. So, if you’ve gone to bed too late, woke up too early, or had poor sleep patterns in any of the other 13 nights before last night, you’ve most likely accrued sleep debt.

That’s why rather than take a close look at your “sleep quality” (even though sleep experts have yet to agree on an official definition for it), sleep debt is the only metric you need to care about if you want to start feeling and functioning at your best when you’re awake.

Improve Your Energy Levels With RISE

Now that we have demystified the seemingly inexplicable sleepiness after eight hours of sleep, what can you do to improve your energy levels?

Firstly, figure out your sleep need. The RISE app can help you with that. RISE decodes your sleep need by using sleep-science-based models and the past 365 nights of sleep data tracked by your phone to learn your unique sleep biology and calculate your sleep need in hours and minutes.

Secondly, pay down your sleep debt and keep it low going forward. You can easily see where your sleep debt stands on the Sleep screen in RISE. We recommend an earlier bedtime, afternoon naps, and, as a last resort, a later sleep-in to effectively chip away at sleep debt.

Instead of relying on sleep aids like melatonin (which are often unnecessary and come with unwanted side effects), work with your circadian rhythm (read: your internal body clock) to promote better sleep at night. Practicing healthy sleep hygiene 24/7 will make it easier to meet your sleep need.

The RISE app can help you do so with its 16 science-based habits. For instance, the “Limit Caffeine” habit tells you when to stop taking the sleep-detracting stimulant based on your unique chronobiology. Meanwhile, the “Block All Blue Light” habit reminds you to steer clear of bright and/or artificial light sources when your bedtime draws near.

You Can Stop Feeling Tired All the Time

Sure, sleep disorders like narcolepsy and restless leg syndrome could be the answers to “Why am I still tired after 8 hours of sleep?” Not to mention fatigue is a hallmark in various health conditions, from thyroid diseases to mental health problems.

But the truth is, the reasons for the ever-present sleepiness are usually non-medical in nature. Most likely, you’re still tired after eight hours of sleep because of these three factors: (1) you don’t know your sleep need, (2) you’re not taking into account your sleep efficiency, and (3) you carry sleep debt.

Fortunately, you don’t have to splurge on a sleep study or consult a doctor well-versed in sleep medicine to boost your daytime energy levels. (Although, if you have an underlying sleep disorder, we recommend you to do so!) Instead, use the RISE app to determine your sleep need, pay down your sleep debt, and maximize your sleep schedule for the better.

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