Feeling sleepy in the daytime most often means you are not getting enough good-quality sleep. Too few hours, broken sleep, shift work, alcohol and some medicines are common reasons. Sleep apnoea, where breathing stops and starts at night, is a common medical cause.
Sleepiness is different from tiredness. The NHS describes excessive daytime sleepiness (hypersomnia) as falling asleep repeatedly during the day. You might nap often, nod off without meaning to, or still sleep long hours at night. Tiredness or fatigue means low energy, without necessarily falling asleep.
If you often fall asleep in the day, or sleepiness is affecting your life, the NHS advises seeing a GP. If you feel drained rather than sleepy, our guide to feeling tired all the time covers blood tests and medical causes of fatigue.
Get help now
Call 112 or 999 in Ireland, 999 in the UK or 911 in the US if someone:
If you feel sleepy while driving: stop somewhere safe. Do not drive again until the sleepiness is under control.
If low mood or thoughts of self-harm are part of this: in Ireland, call Samaritans on 116 123 or text 50808. In an emergency, call 112 or 999. In the UK, call Samaritans on 116 123 or 999. In the US, call 988.
See a GP if:
The difference matters, because it points to different causes. The NHS says hypersomnia is different from feeling tired all the time.
MedlinePlus says depression, anxiety, stress and boredom can all contribute to sleepiness. It adds that these more often cause fatigue and lack of interest. Many people have a mix.
The NHS says adults need 7 to 9 hours of sleep. MedlinePlus lists not sleeping long enough among the causes of drowsiness. So are long working hours, and night or weekend shifts. If your body clock is out of step with your hours, see our guide to jet lag and shift work. For how much sleep you really need, see how much sleep do adults need.
You can spend enough hours in bed but still sleep badly. The HSE describes insomnia as difficulty sleeping 3 or more times a week for more than 3 months. You may wake several times, wake early, feel tired after waking, and find it hard to concentrate in the day.
The NHS says restless legs syndrome is usually worse at night when resting and can affect sleep. Chronic pain is also on MedlinePlus's list of causes of drowsiness.
The NHS says some medicines, drinking too much alcohol and taking drugs can cause excessive daytime sleepiness. MedlinePlus lists tranquillisers, sleeping pills, antihistamines, some painkillers and some psychiatric medicines.
Do not stop or change a prescribed medicine yourself. Ask your GP or pharmacist whether a medicine could be the cause.
The NHS describes sleep apnoea as breathing that stops and starts while you sleep. Night-time signs include gasping, snorting or choking noises, waking up a lot and loud snoring. During the day you may feel very tired, find it hard to concentrate, have mood swings or wake with a headache.
The NHS suggests asking someone to watch you sleep, and bringing them to the GP. It says sleep apnoea needs treatment because it can lead to more serious problems. The STOP-BANG questions are a quick screen you can do at home.
The NHS lists depression and bipolar disorder among conditions linked to excessive sleepiness. Depression often comes with low mood and little interest in things. If this sounds like you, a GP can help. If you are struggling to cope, use the numbers in the box above.
MedlinePlus lists diabetes, an underactive thyroid, and changes in blood sodium or calcium among causes of drowsiness. The NHS links ME/CFS with sleepiness, alongside problems recovering after activity. The NHS also lists excessive daytime sleepiness among the possible symptoms of Parkinson's disease, linked to poor sleep at night.
The NHS describes narcolepsy as a rare condition causing sleepiness and muscle weakness you cannot control. Symptoms can include:
Symptoms usually start in children and young adults. Diagnosis often takes years; we explain why in narcolepsy: why diagnosis takes years.
The NHS describes idiopathic hypersomnia as sleeping for long periods and waking confused, irritable and unrefreshed. This is called sleep inertia. There is no known cause.
This is not a way to diagnose yourself. It shows the details doctors find useful.
The NHS says a GP may ask about mental or physical health problems and your medicines. They may suggest a sleep diary. MedlinePlus lists questions such as:
It helps to bring a partner or housemate who has seen you sleep. MedlinePlus lists possible blood tests, including blood count, blood sugar, salts, calcium and thyroid levels.
The GP may refer you to a sleep clinic. For sleep apnoea, the NHS says you may be given devices to wear overnight, usually at home. For narcolepsy, tests may include an overnight sleep study and a daytime test of how quickly you fall asleep. Our guide to sleep studies explains what to expect.
Falling asleep at the wheel is dangerous. MedlinePlus says do not drive when drowsy.
The NHS says changing sleep habits may not cure hypersomnia, but it might help you feel better. The NHS and HSE suggest:
For narcolepsy, the NHS says planned daytime naps may be recommended. Ask your specialist what suits you.
Time in bed is not the same as good sleep. Broken sleep from sleep apnoea, restless legs or waking often can leave you sleepy. Alcohol and some medicines can also play a part. If it keeps happening, see your GP.
The NHS advises seeing a GP if you often fall asleep during the day, or sleepiness affects your life.
Usually it points to poor or short sleep, or a treatable sleep disorder such as sleep apnoea. Sudden drowsiness with confusion, a head injury or a severe headache is an emergency.
The NHS lists depression among the conditions linked to excessive daytime sleepiness. Depression is treatable. Talk to your GP.
This article is general information, not medical advice. It cannot diagnose the cause of your symptoms. If someone is suddenly very drowsy or confused, call 112 or 999 (Ireland), 999 (UK) or 911 (US). Talk to your GP or pharmacist before starting, stopping or changing any medicine.
Reviewed by: Proco Team
Last updated: November 2026