For most adults, more than 9 hours of sleep a night counts as too much, though it is not always harmful. The Sleep Foundation defines oversleeping as sleeping more than nine hours in 24 hours (Sleep Foundation). Yes, you can sleep too much, but the research is more nuanced than the headlines. This guide covers how many hours is too much, why it happens, what long-sleep studies do and do not show, and when to see a doctor. It is for education only.
Not sure how long you should sleep? Try the sleep calculator by age and gender.
What Counts As Oversleeping?
Most adults need between seven and nine hours (Sleep Foundation). The CDC lists 7 or more hours for ages 18 to 60, 7 to 9 for ages 61 to 64 and 7 to 8 for ages 65 and over. Teens aged 13 to 17 need 8 to 10 hours (CDC). So the answer to how many hours of sleep is too much depends on your age. Ten hours is normal for a young teen and long for a 70-year-old.
The American Academy of Sleep Medicine and the Sleep Research Society add an important point. More than 9 hours may be appropriate for young adults and for people recovering from sleep debt or illness. For others, it is uncertain whether sleeping more than 9 hours is linked to health risk (AASM and SRS consensus).
Is 9 Hours Of Sleep Too Much?
Not by itself. Nine hours sits at the top of the normal 7 to 9 hour band, and plenty of healthy people feel best there. A single long night after a hard week is also normal. Use this table as a guide:
| Hours | What It Usually Means |
|---|---|
| Under 7 | Often too little for adults (CDC) |
| 7 to 9 | The usual adult range (Sleep Foundation) |
| More than 9 | Oversleeping by definition. Fine for some, worth a look if it is new and constant (AASM and SRS consensus) |
| 10 or more, most nights | Worth a check if you feel unrefreshed |
| 12 or more a day, regularly | Could be a sign of an underlying issue (Sleep Foundation) |
If you are an adult who needs 7.5 or 8 hours, see is 7.5 hours of sleep enough. For the full by-age picture, read how much sleep you need.
Common Causes Of Oversleeping
Most causes are temporary and harmless, such as catching up on sleep debt (Sleep Foundation). Longer-lasting causes include:
- Sleep debt. After a short week your body takes extra sleep back. See how to recover from sleep debt.
- Poor sleep quality. Breathing pauses from sleep apnea break up sleep, so you may need more time in bed (Sleep Foundation). Read sleep apnea health risks.
- Depression and anxiety. Both are listed among chronic causes of long sleep (Sleep Foundation). See sleep and depression.
- Sleep disorders. The NHS lists narcolepsy, sleep apnoea, restless legs syndrome, bipolar disorder and ME or chronic fatigue syndrome as possible causes of excessive sleepiness, and notes that some medicines can contribute (NHS).
Your schedule matters too. A shifting bedtime can make you feel like you need more sleep. Read social jet lag.
Oversleeping Side Effects: What The Research Shows
You will see claims that oversleeping raises the risk of early death and disease. The studies exist, but they show links, not proof.
| Study | People | Finding for Long Sleep |
|---|---|---|
| Cappuccio et al. 2010 | About 1.38 million, 16 studies | 30 percent higher risk of death (Cappuccio et al. 2010) |
| Yin et al. 2017 | Meta-analysis of cohorts | Lowest risk near 7 hours. Each extra hour above 7 linked to 13 percent higher risk of death (Yin et al. 2017) |
| Jike et al. 2018 | 137 cohorts, about 5.1 million | 39 percent higher risk of death, higher diabetes and heart disease risk, but no clear link to high blood pressure (Jike et al. 2018) |
Now read the fine print. The authors of the 2010 study say the result may be explained by residual confounding and illness, and ask whether long sleep is a cause or simply a marker of ill-health (Cappuccio et al. 2010). They list depression, low income, low activity and undiagnosed disease as possible confounders, and note that all sleep was self-reported. The 2017 authors cannot rule out residual or unmeasured confounding, and call the mechanisms for long sleep more speculative (Yin et al. 2017). The 2018 review concludes that future studies should address whether the link is causal (Jike et al. 2018).
In plain words: people who sleep very long are, on average, less healthy, but the long sleep may be a sign of the problem rather than the cause.
Why You Can Feel Worse After Sleeping More
If you wake up groggy after a long sleep, it is probably not a sign you slept too little. Cleveland Clinic says sleep inertia, the groggy state after waking, usually lasts 15 to 60 minutes. It suggests skipping the snooze button, getting sunlight soon after waking and keeping naps short (Cleveland Clinic). A shifting schedule can also cause jet-lag-like fatigue, and the University of Colorado advises keeping weekday and weekend schedules consistent, with bedtime changes limited to about an hour (CU Anschutz). For more, read how to get rid of sleep inertia and waking up tired after 8 hours.
How To Stop Oversleeping
- Fix your wake time. The CDC advises getting up at the same time every day (CDC).
- Get daylight early. The Sleep Foundation lists daylight exposure among its tips (Sleep Foundation).
- Keep the bedroom cool, dark and quiet, and take naps early in the day (Sleep Foundation).
- Keep a sleep diary for two weeks. It helps a doctor if you need one (Sleep Foundation).
- Pull the alarm earlier in small steps. Shift by 15 to 30 minutes at a time.
Work out a wake time and count back with the bedtime calculator, and see the best time to wake up.
When Long Sleep Needs A Check
Sleeping a lot is not always a habit problem. Some conditions cause an excessive need to sleep. Cleveland Clinic describes idiopathic hypersomnia as sleeping more than 11 hours in 24 hours, including naps, or more than nine hours at night, with trouble waking and feeling unrested. It advises seeing a provider if you are exhausted in the daytime after sleeping through the night (Cleveland Clinic). The NHS says narcolepsy is rare and can cause sudden sleep and tiredness you cannot control (NHS).
Doctors sometimes use the Epworth Sleepiness Scale. Scores over 10 are considered to reflect excessive daytime sleepiness, but the Sleep Foundation stresses that the score alone is not definitive (Sleep Foundation). It is not a diagnosis.
Quick Takeaways
- More than 9 hours is the usual definition of oversleeping for adults.
- Occasional long nights, and long nights after sleep loss, are normal.
- Studies link very long sleep to poorer health, but long sleep may be a marker, not the cause.
- Constant long sleep with daytime exhaustion deserves a medical check.
- A fixed wake time and morning light are the simplest fixes.
When To See A Doctor
The NHS advises a non-urgent GP visit if you often fall asleep during the day or your sleepiness is affecting your life (NHS). Also see a doctor if you sleep very long hours and still feel unrefreshed, or someone notices pauses in your breathing. Our guide to signs you have a sleep disorder lists more clues.
FAQs About Oversleeping
Is 8 Hours Of Sleep Too Much?
No. Eight hours sits in the middle of the 7 to 9 hour range for most adults (Sleep Foundation, CDC).
Why Do I Sleep So Much?
Common reasons include sleep debt, poor sleep quality, depression, anxiety and sleep disorders (Sleep Foundation, NHS). A doctor can sort them out.
Is 10 Hours Of Sleep Bad For You?
Not automatically. It is normal for young teens and may be fine after sleep loss. If it is constant and you feel unrefreshed, get it checked (CDC, AASM and SRS consensus).
Does Oversleeping Make You Tired?
It can, through sleep inertia or a shifting schedule, which usually fades within an hour (Cleveland Clinic).
Is 10 Hours Too Much For A Teenager?
No. The CDC lists 8 to 10 hours for ages 13 to 17 (CDC).
Can Oversleeping Shorten Your Life?
Studies link very long sleep to higher death risk, but authors warn that long sleep may be a marker of illness rather than a cause (Cappuccio et al. 2010, Jike et al. 2018).
Sources
- Sleep Foundation (oversleeping)
- CDC (about sleep)
- AASM and SRS consensus (Watson et al. 2015)
- NHS (excessive daytime sleepiness)
- NHS (narcolepsy)
- Cleveland Clinic (sleep inertia)
- Cleveland Clinic (idiopathic hypersomnia)
- Cappuccio et al. 2010
- Yin et al. 2017
- Jike et al. 2018
- Sleep Foundation (Epworth scale)
- CU Anschutz (social jet lag)