Still Tired After 8 Hours of Sleep? A Sleep Doctor Explains

You’ve had eight hours of solid sleep. You should be jumping out of bed ready to take on the day, right? 

Well, that’s not always the case. Even after eight hours, you might find yourself snoozing your alarm clock, feeling groggy all morning, and reaching for stimulants like coffee just to get you through the afternoon. 

If this is you, don’t fret. There are some likely culprits behind feeling tired after a full night’s sleep and — luckily — they can be fixed. 

Below, we’ll dive into four reasons you may feel tired after eight hours of sleep and how you can use the RISE app to fix them. 

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It’s normal to feel sleep inertia, or grogginess, when we first wake up. But if this feeling lingers all day long, even after eight hours of sleep, here’s what could be to blame. 

1. Your Sleep Need is More Than 8 Hours 

We all have a unique sleep need, or an amount of sleep we need each night. This is determined by genetics — just like height and eye color — and it’s not simply eight hours for everyone. 

One study suggests the average sleep need is 8 hours 25 minutes, plus or minus 10 minutes or so, but 13.5% of the population may need 9 hours or more sleep a night.

When we looked at sleep need data from 1.95 million RISE app users aged 24 and up, we found the median sleep need was eight hours, but 48% of users need eight hours or more sleep a night.

The “eight hours of sleep” recommendation is a guideline, and one that’s based on how much sleep people get, not how much they need. Sleep experts agree it’s a good place to start, but these guidelines don’t take into account our individual needs. 

Even if you do need exactly eight hours, there are times in life when your sleep need is higher than usual. This includes after intense exercise, like a marathon, and when you’re recovering from an illness, like COVID. 

So, you may be getting eight hours of sleep because you’ve heard that’s the recommended amount, but you may well need more than that to feel your best.

The fix: RISE can work out your unique sleep need, so you know whether you should be aiming for more than eight hours a night.

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

2. You Overestimate Your Sleep Time 

We hate to break it to you, but if you think you’re getting eight hours of sleep a night, you may be getting less. 

Many of us look at our time in bed when we think about sleep. But if you get into bed at midnight and out at 8 a.m., that doesn’t equal eight hours of solid sleep. 

You need to take into account sleep efficiency. This is the measure of how long you spend in bed actually sleeping. It includes the time it takes you to fall asleep and any time you’re awake during the night. 

Even with sleep efficiency in mind, working out how much shut-eye you get is no easy feat. Research shows self-reported sleep data is notoriously inaccurate, and even wearable devices can get it wrong. They can confuse pre-bed screen time for sleep, for example, so you may be given an inflated number. 

All this is to say, you might be spending the right amount of time in bed, but not enough time actually sleeping.  

The fix: Give yourself more time in bed to make sure you meet your sleep need. There’s no magic rule, but an extra 30 minutes to an hour should account for the time it takes to fall asleep and any nighttime awakenings. 

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3. You’ve Got Sleep Debt 

Sleep debt is the running total of how much sleep you owe your body. It’s compared against your sleep need. Here at RISE, we measure it over your last 14 nights. 

So, if you need eight hours of sleep a night, but you’ve only been getting six hours lately, you’ll have built up quite a bit of sleep debt.

Even when you get a full night’s sleep, you may still feel sleepy when you wake up because you’ve got lingering sleep debt. Your body wants more sleep to make up for what it’s lost out on. 

You might have high sleep debt because you’re simply not giving yourself enough time to sleep at night. But a medical condition, sleep problems like insomnia, or a challenging time of life (like when you’ve got anxiety or going through menopause) may also be making it harder to get enough sleep. 

Sleep debt doesn’t just leave you feeling tired. It can lead to health issues like high blood pressure, stroke, diabetes, and obesity. 

This is why it’s so important to keep an eye on your sleep debt. Metrics like sleep quality or time spent in REM or deep sleep are interesting. But research shows total sleep time and sleep efficiency have the biggest impact on how you feel the next day. These are reflected in how much sleep debt you have. 

The fix: RISE can work out how much sleep debt you’ve got. We recommend keeping this below five hours to maximize your energy levels. 

You can pay back sleep debt by: 

• Taking naps 
• Going to bed a little earlier 
• Waking up a little later
• Improving your sleep hygiene, which will help you fall asleep faster and wake up less often during the night. 

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

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4. You’re Out of Sync With Your Circadian Rhythm 

Your circadian rhythm is your roughly 24-hour body clock. It dictates the timing of your sleep cycle, your body temperature fluctuations, and when you produce certain hormones. 

If you’re out of sync with it — by working night shifts or sleeping at irregular times — you’ll be left with low energy. And this low energy can happen even if you’re getting enough sleep overall. 

One sleep study looked at two groups of participants who got the same amount of sleep, but one group got this sleep on a regular schedule. This group with regular sleep patterns felt more energy and alertness. 

Being out of sync with your circadian rhythm can also make it hard to fall asleep at bedtime, which can lead to high sleep debt and even more sleepiness.

The fix: Find a sleep schedule that works for you and stick to it, even on your days off. 

RISE can predict your circadian rhythm each day and show you when your body naturally wants to wake up and go to sleep. You can then work to stay in sync with these times. 

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

A Sleep Doctor Weighs In 

We asked our sleep advisor and medical reviewer, Dr. Chester Wu, for his take on why you might be tired still after eight hours of sleep. 

“If you’re getting eight hours of sleep and still feeling tired each day, you may need more rest than that. Eight hours is a good starting point, but we all need a different amount of sleep. Try heading to bed a little earlier than usual and seeing how you feel.” Rise Science Medical Reviewer Dr. Chester Wu

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We’ve covered that one common reason you may feel tired after eight hours of sleep is because you need more than eight hours. But how do you know how much you need? There are two ways to find out. 

The Manual Way 

Try waking up without an alarm clock for at least a week (ideally two) and tracking how long you sleep for. 

It sounds easy, but the manual way of working out your sleep need has a few problems, including: 

• It’s hard to go a whole week without needing an alarm clock — let alone two! 
• It’s hard to work out how much sleep you got exactly. 
• Your body may be taking the chance to pay down sleep debt. 

The Accurate Way 

The more accurate (and easier!) way to work out your sleep need is by turning to RISE. The app uses a year’s worth of phone use behavior and proprietary sleep-science-based models to work out your sleep need down to the minute. 

RISE also works out your sleep debt, so you know if your body wants to temporarily sleep for longer to play catch up.

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

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You may feel sleepy after a full night’s sleep due to a medical condition. 

Medical conditions that can make you tired, or make it hard to meet your sleep need, include: 

• Sleep disorders like obstructive sleep apnea, narcolepsy, and restless leg syndrome 
• Iron deficiency anemia 
• Hypothyroidism (underactive thyroid) 
• Diabetes 
• Mental health problems like depression and anxiety
• Heart disease 
• Chronic fatigue syndrome

You might also feel tired from nutritional deficiencies, as a side effect of medication, or because pregnancy, menopause, or your period are making it harder to sleep.

If you’re meeting your sleep need, keeping your sleep debt low, staying in sync with your circadian rhythm, and you’re still feeling tired the next day, it might be worth speaking to a doctor. 

We’ve covered more on why you’re always tired here, including why it’s normal to feel tired when you first wake up and in the afternoon. 

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Now you know why you’re most likely feeling tired after eight hours of sleep, it’s time to fix that. 

Here’s how you can enjoy more energy each day: 

• Meet your sleep need: Use RISE to work out your sleep need and start aiming for that amount of sleep each night. Remember to add a buffer of 30 minutes to an hour to account for any time awake in bed.
• Pay down sleep debt: Take a nap or head to bed a little earlier tonight. Aim to keep your sleep debt below five hours to maximize your energy levels.
• Sync up with your circadian rhythm: Keep a consistent sleep schedule and try to keep meals to regular times, too. 
• Improve your sleep hygiene: RISE can walk you through 20+ healthy sleep habits, such as when to get and avoid blue light and when to avoid caffeine, large meals, intense exercise, and alcohol. RISE can also remind you to check your sleep environment before bed. This will help you get better sleep each night. 

Need a quick pick-me-up? We’ve covered ways to wake yourself up here. But remember, for more energy long-term, low sleep debt and syncing up with your circadian rhythm are vital. 

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

You Can Stop Feeling Tired All the Time 

We’re told all the time to get our eight hours of shut-eye. So when you’re getting eight hours and still feeling tired the next day, it’s frustrating. 

There are four likely culprits behind your low energy: your sleep need is more than eight hours, you’re getting less sleep than you think, you’ve got sleep debt to pay back, or you’re out of sync with your circadian rhythm. 

To help, the RISE app can work out your individual sleep need, so you know what to aim for. Then, the app can calculate how much sleep debt you have and keep track of it as you pay it back. And it can predict your circadian rhythm each day, so you can sync up with it.

To make getting a good night’s sleep easier, RISE can also guide you through 20+ sleep hygiene habits each day.

All this will lead to more sleep and more energy. And it can happen sooner than you think: 80% of RISE users feel the benefits within five days.