Why do I feel more tired after sleeping longer
If you have ever asked yourself, “why do I feel more tired after sleeping longer?”, you are far from alone. A long sleep can leave you groggy because you are more likely to wake from deeper sleep (sleep inertia), because a lie-in nudges your body clock later, and because needing extra sleep often means your usual sleep is poor or short. The grogginess usually clears in 15 to 30 minutes. If it does not, see a GP.
You give yourself a Saturday lie-in, wake at 11, and still feel as if you have been hit by a lorry. If grey mornings are already dragging you down, our guide on how to beat winter fatigue and wake up feeling refreshed is a good companion to this one.
It matters now because the clocks go back on Sunday 25 October 2026, handing most of us an extra hour in bed.
What is sleep inertia
Sleep inertia is the groggy, slowed-down state you pass through between sleep and full alertness. Your brain takes a little while to come fully online, which is why you might put the milk in the cupboard.
In a review in Nature and Science of Sleep, Dr Cassie Hilditch and Dr Andrew McHill describe sleep inertia as a kind of buffer between sleeping and waking, shaped by how much sleep pressure you have built up and where you are in your body clock. It tends to be stronger when you wake from deep sleep, or at a time your body expects to be asleep.
How long does it last in everyday life? A 2026 study in PLOS One asked 2,355 adults in South Korea how long it usually took them to shake off morning grogginess. The average was 15.8 minutes, although some people took much longer.
Why a lie-in can throw off your body clock
Your body clock, or circadian rhythm, runs on a cycle of roughly 24 hours and is reset each day mainly by light.
When you sleep two or three hours past your usual time, you are not just topping up sleep. You are also shifting that rhythm later. You may then wake at a moment your body was not preparing for, often partway through a sleep cycle, and that can leave you foggier than a normal weekday alarm would.
Is it sleep quality, not quantity
Often, yes. A long sleep is often your body paying back a debt. If you have been sleeping badly or too little during the week, a 10-hour Saturday is your system catching up, and the tiredness you feel was already there before the lie-in began. This is one answer to the question “why do I wake up tired after 8 hours of sleep?”: eight hours in bed is not the same as eight hours of good, unbroken sleep.
Interestingly, the Korean study found that people who usually slept less than six hours reported longer morning grogginess than those who slept more than eight, and insomnia was linked to longer grogginess too. So the long sleep itself is rarely the whole story. Broken sleep, snoring, a hot bedroom, and evening alcohol all chip away at quality. If lying awake trying to force sleep is part of the problem, it is worth reading about why the harder you try to sleep, the more awake you become.
For people who wonder “why am I still tired after sleeping 10 hours?”, the NHS points out that ongoing tiredness can have causes that more sleep will not fix, including sleep apnoea, iron deficiency anaemia, diabetes, and an overactive thyroid.
How anxiety and low mood feed morning grogginess
Your mind plays a bigger part in morning fog than many people expect. In the same 2026 study, people with anxiety took about 14 minutes longer to clear their grogginess than people without it, and anxiety had the strongest link of any factor the researchers looked at. Night owls also took longer to feel alert than early birds.
Some people with depression sleep less, while others sleep for long stretches and still wake unrested. The NHS lists stress, depression, and difficult life events such as bereavement among the common causes of tiredness. The study cannot show that anxiety causes grogginess, but it fits what many people notice.
Will the extra hour when the clocks go back make you more tired
For most people, probably not for long. A large study in The BMJ, which looked at the health records of 683,809 people in England between 2008 and 2019, found slightly fewer recorded cases of anxiety, depression, and sleep disorders in the week after the autumn clock change than in the weeks around it. Sleep disorder events fell by about 8%, depression by about 4%, and anxiety by about 3%. These are modest findings, and records show when a doctor logged a problem rather than when it began.
Where people do feel worse is when they use the extra hour as an excuse for a long lie-in and a late night, which pushes the body clock later just as the evenings get darker. See how to reset your body clock when the clocks go back for tips on the week ahead.
How to wake up feeling less groggy
These habits help shorten sleep inertia:
- Keep a steady wake time: Try to get up within an hour of your usual time, even at weekends. The NHS suggests sticking to the same sleep times and aiming for 6 to 9 hours.
- Get light early: Open the curtains, step outside, or sit by a window soon after waking. Light resets your body clock.
- Skip the snooze button: Drifting back to sleep for nine minutes can drop you into a new sleep cycle, so the second alarm often feels worse than the first.
- Move a little: A short walk, a shower, or a few stretches help your brain come online.
- Give yourself a buffer: If you know you take 20 minutes to feel clear, set your alarm 20 minutes earlier rather than rushing into decisions or driving straight away.
- Look after the evening: Avoid caffeine, heavy meals, and alcohol in the couple of hours before bed, and put screens away an hour before sleep.
Our guide to autumn sleep struggles and how to fix them covers the seasonal side in more detail.
When tiredness after sleep needs a GP
Occasional grogginess after a lie-in is normal. It is worth booking a GP appointment if any of these apply to you, according to the NHS advice on tiredness and fatigue:
- you have felt tired for a few weeks and do not know why
- tiredness is affecting your daily life, work, or relationships
- you have other symptoms too, such as weight loss or mood changes
- someone has told you that you gasp, snort, or choke in your sleep
A GP may suggest blood tests for problems such as anaemia, diabetes, or thyroid issues. Talking therapies, including cognitive behavioural therapy, can help when tiredness is tangled up with anxiety, low mood, or insomnia.
FAQs
- Is it bad to sleep 10 hours? Not on its own, especially if you are catching up or unwell. If you regularly need 10 hours or more and still feel tired, that is a reason to speak to a GP, as it can point to poor sleep quality or an underlying health problem.
- How long does sleep inertia last? For most people it fades within 15 to 30 minutes, and it often lasts longer in people with anxiety, insomnia, or a night owl body clock.
- Why do I feel worse after a nap? A long nap can carry you into deep sleep, so you wake in the middle of it and feel heavy and confused. Keeping naps short, around 20 to 30 minutes, and taking them earlier in the afternoon usually helps.
- Can oversleeping cause headaches? Some people do wake with a headache after a long lie-in. Going longer than usual without food, water, or your usual caffeine may play a part. If headaches are frequent or severe, see a GP.
- Is sleeping too much a sign of depression? It can be. Depression can make some people sleep much more than usual and still wake feeling unrefreshed. If long sleeps come with low mood, loss of interest, or hopelessness, talk to a GP. If you feel unsafe, call 999, or contact Samaritans on 116 123 at any time.
