For most healthy adults, regularly needing more than about nine hours of sleep each night can be a sign that something is amiss. While the occasional lie-in after travel, illness, intense physical activity, or a string of late nights is perfectly normal and usually harmless, consistently sleeping for long periods – especially if you still wake feeling unrefreshed – has been linked in research to a variety of health concerns. It is important to note that much of this evidence is observational, meaning that excessive sleep may often be a marker of underlying issues rather than a direct cause. Nevertheless, it is wise to pay attention to persistent oversleeping and consider what might be driving it.

This can depend on individual circumstances. For adults, regularly sleeping more than nine hours a night, particularly when accompanied by daytime tiredness or poor functioning, is generally considered excessive and may warrant further attention. Teenagers and young adults often require eight to ten hours, and longer sleep can be normal during periods of growth or when repaying sleep debt. Similarly, pregnancy, recovery from illness, and periods of intense training can temporarily increase the need for sleep. There is also a small minority of people who are natural long sleepers; they function well on nine to ten hours and do not experience daytime sleepiness, so for them, longer sleep may simply reflect their biological needs.

Oversleeping has been associated with several adverse health outcomes. People who habitually sleep for very long periods have been found to have higher rates of diabetes, cardiovascular disease, stroke, and even increased overall mortality compared to those who sleep around seven to eight hours. However, it is important to recognise that factors such as depression, unemployment, low physical activity, and undiagnosed illnesses may contribute to this pattern. Many people who oversleep report pronounced sleep inertia – grogginess and disorientation upon waking – alongside persistent daytime sleepiness, reduced concentration, and “brain fog”. Spending excessive time in bed can actually fragment sleep and reduce its quality, paradoxically leaving you feeling more tired.

Long sleep is also common in conditions such as depression, seasonal affective disorder, and during depressive phases of bipolar disorder. In these cases, it can both reflect low mood and, for some, exacerbate it by reducing exposure to daylight and limiting activity. Observational studies have linked longer sleep with higher blood pressure and increased inflammatory markers. Some people also notice morning headaches or migraines after extended sleep, sometimes worsened by caffeine withdrawal or changes in routine. Prolonged time in bed can aggravate back or neck pain and morning stiffness, and lingering sleepiness can slow reaction times and impair judgement, increasing the risk of accidents at home, on the road, or at work.

Many large studies have shown a U-shaped relationship between sleep duration and health risks, with the lowest risk typically found among those who sleep seven to eight hours per night. The harms of chronic short sleep – such as irritability, impaired performance, metabolic dysregulation, and a higher risk of accidents – are well established and causally demonstrated. While long sleep is also associated with negative outcomes, it is more often a signal of underlying sleep, medical, or mental health conditions than a proven cause in its own right. The practical message is to aim for a consistent, healthy window – usually seven to nine hours for adults – and to address either extreme if it persists.

Signs of oversleeping go beyond the occasional weekend lie-in. If you regularly sleep more than nine hours yet wake feeling unrefreshed, struggle to get out of bed, or find yourself repeatedly hitting the snooze button, oversleeping may be part of the picture. Many people notice persistent daytime fatigue despite long nights, morning headaches, low mood or irritability, and difficulties with attention, memory, and motivation. Aching, stiffness, and a general sense of physical discomfort after long periods in bed are also common, and some individuals begin to rely on long daytime naps to get through the day.

There are many possible causes for oversleeping. Sleep disorders such as obstructive sleep apnoea (often signalled by loud snoring and pauses in breathing), restless legs syndrome, periodic limb movements, circadian rhythm disorders, and hypersomnia conditions (including idiopathic hypersomnia and narcolepsy) can all lead to excessive sleep or sleepiness. Mental health conditions, especially depression and seasonal affective disorder, are frequently involved. Medical issues such as hypothyroidism, anaemia due to iron, B12 or folate deficiency, chronic infections, inflammatory illnesses, chronic pain syndromes, and post-viral fatigue can increase sleep need and reduce sleep quality. Medications and substances – including sedating antihistamines, some antidepressants and antipsychotics, benzodiazepines, opioids, alcohol, and cannabis – may also contribute. Lifestyle and environmental factors matter too: limited daylight, low physical activity, irregular schedules, excessive time in bed, and poor sleep environments (such as noise, light, or temperature) can all push sleep longer without improving how you feel. Social and occupational factors such as unemployment, shift work, and caregiving demands can further compound these effects.

Longer sleep is not always a cause for concern. After long travel, acute illness, heavy training, or a period of curtailed sleep, needing more rest for a few days is normal. If you consistently sleep a bit longer – say nine to ten hours – but feel alert, upbeat, and productive without daytime sleepiness, you may simply have a higher physiological sleep need.

If you want to reduce oversleeping and feel better, start by setting a consistent wake-up time every day, including weekends, and establish a regular bedtime that allows an appropriate amount of sleep. Limiting time in bed to roughly the amount of sleep you actually achieve can help consolidate sleep; many people do well with around seven and a half to eight and a half hours. Try to get outside into daylight within an hour of waking and incorporate daily physical activity into your routine.

Optimise sleep quality with a dark, cool, quiet bedroom, a short wind-down period, and by avoiding heavy meals, alcohol, and caffeine late in the day. Keep any naps short and earlier in the afternoon. Tracking your habits with a two-week sleep diary – including bedtimes, wake times, awakenings, naps, caffeine and alcohol intake, exercise, and mood – can reveal patterns.

Consider speaking to your GP if you regularly sleep more than nine hours and still feel tired, if you have loud snoring or witnessed breathing pauses, morning headaches or a dry mouth on waking, or if you experience persistent low mood, loss of interest, or anxiety. Seek advice for new or worsening headaches, notable memory or concentration problems, unintentional weight change, temperature intolerance, or other symptoms that could suggest thyroid or nutritional problems, and for any excessive sleepiness that leads to near misses or accidents. Your GP can review medications, screen for sleep, medical and mental health conditions, and arrange tests or a referral to a sleep clinic if needed.

In summary, occasional long sleep is common and usually harmless, but persistent oversleeping – especially when you wake unrefreshed – is worth addressing. Both too little and too much sleep are linked with poorer health; most adults do best with seven to nine hours of good quality, regular sleep. If oversleeping persists or affects your daily life, look for underlying causes and seek professional advice.

Links

Klerman, E.B., Barbato, G., Czeisler, C.A. & Wehr, T.A. (2021) ‘Can People Sleep Too Much? Effects of Extended Sleep Opportunity on Sleep Duration and Timing’, Frontiers in Physiology, 12, 792942.

Léger, D., Beck, F., Richard, J.B., Sauvet, F. & Faraut, B. (2014) ‘The risks of sleeping “too much”. Survey of a National Representative Sample of 24,671 adults (INPES health barometer)’, PLoS One, 9(9), e106950.

Du, M., Liu, M. & Liu, J. (2023) ‘U-shaped association between sleep duration and the risk of respiratory diseases mortality: a large prospective cohort study from UK Biobank’, Journal of Clinical Sleep Medicine, 19(11), pp. 1923–1932.

John Hopkins Medicine (2025) ‘Oversleeping: Bad for Your Health?’, available at: https://www.hopkinsmedicine.org/health/wellness-and-prevention/oversleeping-bad-for-your-health (Accessed: 18 August 2025).

Parker, H. (2024) ‘Physical Side Effects of Oversleeping’, WebMD, available at: https://www.webmd.com/sleep-disorders/physical-side-effects-oversleeping (Accessed: 18 August 2025).

Meadows, A. (2025) ‘Oversleeping: How Much Sleep Is Too Much?’, Sleep Foundation, available at: https://www.sleepfoundation.org/how-sleep-works/oversleeping (Accessed: 18 August 2025).

Leng, Y. & Yaffe, K. (2020) ‘Sleep Duration and Cognitive Aging—Beyond a U-Shaped Association’, JAMA Network Open, 3(9), e2014008.

Jiang, L. & Xu, H. (2023) ‘U-Shaped Relationship between Sleep Duration and CKD in US Adults: Data from National Health and Nutrition Examination Survey (NHANES) 2005–2014’, American Journal of Nephrology, 54(7-8), pp. 275–280.

Gupta, C. & Rigney, G. (2025) ‘Is sleeping a lot actually bad for your health? A sleep scientist explains’, The Conversation, available at: https://theconversation.com/is-sleeping-a-lot-actually-bad-for-your-health-a-sleep-scientist-explains-259991 (Accessed: 18 August 2025).

Cai, Z., Ye, Y., Chen, S. et al. (2025) ‘U-shaped association between average daily sleep duration and depression among individuals with hypertension: a cross-sectional study based on NHANES 2017–2020’, BMC Psychiatry, 25, p. 608.