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Why Am I So Tired in the Afternoon? A Sleep Doctor Explains

You’re tired in the afternoon due to a natural dip in your energy levels as part of your circadian rhythm. Sleep debt can make the afternoon slump feel worse.
Published
2022-04-18
Updated
2024-01-10
14 MINS
Written by
Jeff Kahn, M.S., Rise Science Co-Founder
Reviewed by
Chester Wu, MD, Rise Science Medical Reviewer
Our Editorial Standards
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.
Woman feeling very tired in the afternoon while at work

Why Am I So Tired in the Afternoon? 

  • You’re tired in the afternoon because there’s a natural dip in your energy levels around 1 P.M. to 4 P.M. as part of your circadian rhythm, or body clock. 
  • This tiredness will feel worse if you haven’t had enough sleep. 
  • The RISE app can predict when this afternoon tiredness will hit, and help you get enough sleep to boost your energy levels in the afternoons and all day long.

You’re feeling energized all morning, but as soon as 3 P.M. rolls around you’re struggling to keep your eyes open. We’ve all been there. The afternoon slump is natural and hits us all to some degree. 

Keep reading to find out why you’re so tired in the afternoon, what makes you feel more tired than usual, and how the RISE app can help you get more energy all day long. 

A Sleep Doctor Explains

“Feeling tired in the afternoon is a natural part of your circadian rhythm. Some fatigue is normal, but if you struggle to keep your eyes open, you might be sleep deprived. Try getting a little more sleep over the next few nights and see if it improves your afternoons.”

Rise Science Sleep Advisor and Medical Reviewer Dr. Chester Wu

Why Am I So Tired in the Afternoon?

You’re tired in the afternoon because your circadian rhythm causes a natural dip in energy, which happens around 1 P.M. to 4 P.M. for many of us. The afternoon slump can feel worse and last longer if you’ve got sleep debt. 

Here’s more on the common culprits of the afternoon slump. 

1. It’s a Natural Part of Your Circadian Rhythm 

 Afternoon tiredness is to be expected as part of the flow of your circadian rhythm. 

Your circadian rhythm is your body’s internal clock. It runs on a roughly 24-hour cycle and dictates your sleep-wake cycle and when you feel sleepy and alert throughout the day.  

Here’s what your energy levels probably look like each day: 

  • Lower energy when you first wake up (this is known as sleep inertia and in the RISE app we call it your grogginess zone) 
  • Higher energy mid-morning as your first energy peak of the day 
  • Lower energy in the afternoon 
  • Higher energy levels again in the early evening 
  • Lower energy levels as you wind down for bed 

Most people will feel the afternoon slump around 1 P.M. to 4 P.M. but the exact timing will all depend on when you woke up that morning and your chronotype, which is whether you’re an early bird or night owl. Early birds can feel their afternoon slump earlier in the day than night owls. 

Want to know when the afternoon slump will hit exactly? RISE predicts your circadian rhythm each day so you can see when your energy levels are expected to dip in the afternoons, and when you can expect them to pick back up again. 

RISE app screenshot showing your energy schedule
The RISE app can predict the timing of your afternoon slump each day.

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

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2. You’ve Got Sleep Debt 

Sleep debt is the measure of how much sleep you owe your body. If you don’t meet your sleep need — the genetically determined amount of sleep you need each night — you’ll build up sleep debt. 

For example, if you need eight hours of sleep a night, but you only get six, you’ll have about two hours of sleep debt. 

Sleep debt can leave you feeling tired all day long, but especially during your afternoon slump. A lack of sleep can also tank your mental performance, mood, and decision-making skills — so you really won’t be at your best during the afternoon.

We’ve covered how to know how much sleep debt you have here. RISE can work this out for you automatically. The app calculates your individual sleep need and how much sleep debt you have.  

RISE app screenshot showing how much sleep debt you have
The RISE app can work out how much sleep debt you have.

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

Heads-up: You may need more sleep than you think. We looked at the sleep needs of 1.95 million RISE users aged 24 and up and found the median was eight hours. But 48% of users need eight hours or more sleep each night. 

It’s easy to think you’re getting enough sleep, but really be carrying sleep debt. Research suggests we generally don’t notice the drop in cognitive performance we get from sleep deprivation

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


3. You’re Out of Sync with Your Circadian Rhythm 

Being out of sync with your circadian rhythm can lead to low energy levels all day, and these can be even lower when your natural afternoon dip in energy rolls around. 

You might be out of sync if: 

  • You work night shifts 
  • You’ve got social jet lag, or an irregular sleep pattern, which about 87% of us do  
  • You’re fighting your chronotype, like a night owl trying to wake up early 

And just like with sleep debt, being out of sync with your circadian rhythm can lower your mental performance.  

If you’re getting enough sleep, but you’re always sleepy, being out of sync could be to blame. 

4. You Had a Heavy Lunch 

Your lunch isn’t to blame for the afternoon slump (again, you can thank your circadian rhythm for that). But a heavy, high-carb, or high-calorie lunch can make it feel worse. 

One study found a heavier lunch was linked to feeling more sleepy and performing worse on a simulated driving test when sleep deprived compared to a light lunch. 

You might also get a blood sugar crash if you had sugary food for lunch. And if you haven’t had enough water, dehydration can make you feel fatigued. 

We’ve covered more on why you feel sleepy after eating here.

5. You’ve Got a Medical Condition or Sleep Disorder 

If you’re always tired, a medical condition or sleep disorder may be to blame. And this may make the afternoons much harder to get through without a nap. 

Medical conditions that contribute to fatigue include: 

  • Anxiety
  • Depression 
  • High blood pressure 
  • Type 2 diabetes 
  • Iron deficiency anemia 
  • Hypothyroidism (underactive thyroid) 
  • Heart disease 

And sleep disorders include: 

Speak to your healthcare provider if you think a medical condition or sleep disorder could be causing your afternoon tiredness. They can run tests to confirm. 

What Are the Symptoms of the Afternoon Slump?

The symptoms of the afternoon slump include: 

How to Stop Afternoon Fatigue?

You can’t necessarily stop afternoon fatigue, it’s a natural part of your circadian rhythm. You can get more energy in the afternoons, though, by lowering your sleep debt and getting in sync with your circadian rhythm. For short-term energy boosts, try listening to music, doing a burst of exercise, or drinking a glass of water. 

Here’s more on those key steps. 

Lower Your Sleep Debt 

You might not be able to escape the afternoon slump altogether, but if you’ve got high sleep debt, catching up on sleep can make the slump feel more manageable. 

You can lower your sleep debt by: 

  • Taking naps: Keep these short and early in the day (the afternoon slump is the ideal time if you're sleepy anyway) so you can still fall asleep at night.  
  • Going to bed a little earlier: We’ve covered advice on how to sleep early here. 
  • Sleeping in a little later: Keep this to an hour to two to avoid disrupting your circadian rhythm. 
  • Improving your sleep hygiene: Sleep hygiene is the set of daily habits you can do to fall asleep faster and wake up less often during the night, so you’ll get more sleep overall. RISE can guide you through 20+ sleep hygiene habits each day. 

We recommend aiming for five hours of sleep debt. While zero is a great goal, it can be unrealistic. Research suggests your mental performance with five hours of sleep debt is roughly comparable to what it would be with no sleep debt at all. 

Lowering your sleep debt is key to getting more energy, and this is especially important if you find yourself falling asleep at work or falling asleep while driving during the afternoons.

RISE app screenshot shows your sleep habit reminders
The RISE app can tell you when to do 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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Get in Sync With Your Circadian Rhythm 

Get in sync with your circadian rhythm to increase your energy levels. 

You can get in sync by: 

  • Keeping a regular sleep schedule: Research shows those with a consistent sleep schedule have more energy than those who get enough sleep on an irregular schedule. And RISE users with a consistent sleep schedule have lower sleep debt than those with an inconsistent sleep schedule. 
  • Eat meals at roughly the same times: Your eating habits can mess with your sleep and energy. Eat at regular times and avoid eating late in the evening or at night. A 2023 study found time-restricted eating — when you eat your meals within a set time frame like 8 A.M. to 8 P.M. — was linked to getting more sleep — which will help you feel less tired. 
  • Going to bed when your body naturally wants you to: Look for your Melatonin Window in the RISE app. This is when your body’s rate of melatonin production (the sleep hormone) will be at its highest, so you’ll have an easier time falling asleep and staying in sync.

Work With Your Afternoon Slump — Not Against It 

Work smart, not hard, and plan your day to match your energy levels. 

Schedule challenging tasks — like coding, writing, or sales calls — for your morning peak in energy. And save easy tasks — like email, admin, or casual meetings — for your dip in energy. 

Your afternoon dip in energy is also a great time to take a break, get some exercise, or take a nap, which can give you more energy for the rest of the afternoon.

Check RISE for when your peaks and dips in energy will be each day. You can also integrate these predictions into your Apple or Google calendar to help you make the most of them. 

You can also find out when you’re most productive here, including the types of tasks you might be better at during the afternoon. 

Take a Nap 

Need to feel more awake in the afternoon? Try taking an early afternoon nap. 

Research shows naps can improve: 

  • Alertness
  • Reaction times
  • Accuracy 
  • Mood 

If you’ve got sleep debt, naps can also help you chip away at this to boost your energy levels long term. 

And you don’t need to nap for long. One study found a 10-minute power nap is enough to boost energy levels and cognitive performance. And some of the benefits lasted 2.5 hours, which should help you get through the rest of the afternoon. 

Try Short-Term Energy Boosts 

The best thing you can do to feel more energy is to focus on lowering your sleep debt and living in sync with your circadian rhythm. But sometimes, the afternoon slump hits and you need a pick-me-up. 

You can wake yourself up by: 

  • Doing a quick burst of exercise (even a 10-minute walk can help) 
  • Practicing yoga nidra or NSDR
  • Drinking a glass of water 
  • Taking a cold shower or splashing your face with cold water
  • Having a conversation 
  • Playing your favorite music 
  • Eating a healthy snack (remember to steer clear of high-carbohydrate meals) 
  • Not chewing gum (it may decrease alertness levels)

Expert tip: Avoid caffeine. Yes, it’s tempting to reach for a cup of coffee to get you through the afternoon, but caffeine can linger in your system for more than 12 hours. And a 2023 paper found caffeine can reduce your total sleep time by 45 minutes. So an afternoon coffee may keep you up at night, making you even more tired the next afternoon.

We’ve covered more ways to beat the afternoon slump here. 

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Feel More Alert in the Afternoons 

It’s natural to feel tired in the afternoon as your energy levels naturally rise and fall over the course of the day as part of your circadian rhythm. But your afternoon slump will feel worse if you’ve got high sleep debt or you’re out of sync with your circadian rhythm. 

The RISE app can work out how much sleep you need, how much sleep debt you have, and predict your circadian rhythm each day to help you sync up with it. RISE can also guide you through 20+ good sleep habits to help you get a good night’s sleep for more energy the next day. 

Plus, RISE can tell you when your afternoon dip in energy is expected to be each day, and when your energy levels are expected to pick up again, so you can plan your day around it. 

We found 80% of RISE users feel more energy within five days, so you could soon be feeling better in the afternoon.

FAQs

Why am I so tired in the afternoon?

You’re so tired in the afternoon because your energy levels naturally drop in the afternoon as part of your circadian rhythm. This afternoon dip in energy can feel worse if you’re sleep deprived, out of sync with your circadian rhythm, had a heavy lunch, or have a medical condition or sleep disorder.

Why am I always tired in the afternoon?

You’re always tired in the afternoon because your energy levels naturally drop in the afternoon as part of your circadian rhythm. This afternoon dip in energy can feel worse if you’re sleep deprived, out of sync with your circadian rhythm, had a heavy lunch, or have a medical condition or sleep disorder.

Why do I feel tired in the afternoon but not at night?

You feel tired in the afternoon but not at night because of your circadian rhythm. You’ll have a natural drop in energy in the afternoons, but then your energy levels will pick up again in the early evening. You might feel awake at night because of poor sleep hygiene, which includes having coffee, alcohol, a nap, or a large meal too close to bedtime.

Afternoon fatigue

Afternoon fatigue is most likely caused by your circadian rhythm as your energy levels naturally drop in the afternoon. This afternoon dip in energy can feel worse if you’re sleep deprived, out of sync with your circadian rhythm, had a heavy lunch, or have a medical condition or sleep disorder.

Extreme mid-afternoon fatigue

Extreme mid-afternoon fatigue is most likely caused by sleep deprivation making your natural afternoon dip in energy, which is part of your circadian rhythm, feel worse. This afternoon dip in energy can also feel worse if you’re out of sync with your circadian rhythm, had a heavy lunch, or have a medical condition or sleep disorder.

How long does the afternoon slump last?

The afternoon slump can last a few hours between 1 P.M. and 4 P.M. If you’re sleep deprived, the afternoon dip in energy can last longer. And the timing of it will depend on your sleep times and your chronotype. The afternoon slump can hit early birds earlier in the afternoon than night owls.

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