Last updated: October 2026
Usually you can’t sleep because something is keeping your brain on alert: stress and racing thoughts, caffeine or alcohol too late in the day, an irregular schedule, screens, or a bedroom that’s too warm or noisy. Worrying about sleep then keeps it going. If it lasts for weeks, see a GP to rule out insomnia, sleep apnoea, hormones or medicines.
This guide helps you work out which one is you. Start with the symptom table, try the “tonight” steps if you’re reading this in bed, then follow the links to our detailed guides for your cause.
Match your symptom to the likely cause
How you can’t sleep is a big clue to why. Find the row that sounds most like your nights.
| What happens | Most likely causes | Read next |
|---|---|---|
| Can’t fall asleep: you lie awake for ages after lights out | Racing thoughts, caffeine after lunch, screens and bright light late in the evening, a body clock that runs late, worrying about not sleeping | How to fall asleep fast |
| Wake at 3am and can’t get back to sleep | Alcohol wearing off, stress, needing the loo, night sweats, snoring or sleep apnoea | Why do I wake up at 3am? |
| Wake too early (4 or 5am) and stay awake | Low mood (the NHS lists waking very early as a sign of depression), a light bedroom at dawn, going to bed very early, a body clock that runs early | Fix your sleep schedule |
| Tired but wired: exhausted all day, alert at bedtime | Stress, late caffeine, evening screens, an irregular schedule | Tired but wired |
| Can’t sleep even when you’re exhausted, night after night | Your brain has learned to link bed with being awake (conditioned arousal), anxiety, long-term insomnia | Insomnia |
| Mind races the moment your head hits the pillow | Worry, anxiety, an unfinished to-do list | Anxiety at night |
| Snoring, gasping or waking a lot, then sleepy all day | Sleep apnoea | Sleep apnoea |
| An urge to move your legs as soon as you lie down | Restless legs syndrome, sometimes linked to low iron or pregnancy | Restless legs |
| Worse in the week before your period, or hot, sweaty nights in your 40s | Hormone changes, perimenopause | Perimenopause and sleep |
More than one row fits? That’s common. Two or three causes often stack up, such as a stressful week plus a late coffee plus a warm room.
Everyday reasons you can’t sleep
Sleep problems are very common. A major review of more than 50 population studies found that about a third of people have at least one insomnia symptom, though only around 6% meet the full criteria for an insomnia diagnosis. For most people the cause is in this list.
1. Stress and racing thoughts
Stress, anxiety and depression top the NHS list of common causes. When your mind is busy, your body stays in alert mode, and that’s the opposite of the calm state you need to drift off. If thoughts loop at bedtime, see how to stop overthinking.
2. Caffeine, alcohol and nicotine timing
The NHS advises no tea, coffee, alcohol or smoking in the 6 hours before bed. In one sleep study, a strong dose of caffeine taken 6 hours before bedtime still disrupted sleep compared with a placebo. See how long caffeine lasts to set your cut-off. Alcohol works the other way round: a review of sleep studies found it helps you fall asleep faster but increases disrupted sleep in the second half of the night, which is why a few drinks so often mean a 3am wake-up. Read alcohol and sleep.
3. An irregular schedule
Going to bed and getting up at different times confuses your body clock. Late weekends, shift work and jet lag all do the same. The NHS says going to bed and getting up at similar times each day helps your body know when it’s time to sleep. Our 7-day sleep schedule reset walks you through it.
4. Screens and evening light
Bright light in the evening tells your brain it’s still daytime. In a controlled study, people who read on a light-emitting tablet before bed took longer to fall asleep, released less melatonin and felt less alert the next morning than when they read a printed book. The NHS suggests putting phones, tablets and computers away for an hour before bed.
5. A bedroom that’s too warm, light or noisy
Noise, light, being too hot or cold, and an uncomfortable bed are all on the NHS list. Heat is the bigger problem in real life: in a review of sleep research, a warm bedroom with normal bedding increased time awake and reduced deep sleep. See the best temperature for sleep for what to aim for. If you can’t control street noise or early light, earplugs and a sleep mask are cheap fixes the NHS itself suggests.
6. Naps and lie-ins
A long afternoon nap or a lie-in after a bad night eases your tiredness, but it also uses up the sleep pressure you need at bedtime. That’s why the NHS advises against napping during the day and sleeping in after a poor night if you have insomnia.
7. Worrying about sleep itself
This is the cause most people miss. After a run of bad nights, you start to dread bedtime, check the clock and try hard to sleep. Your brain then learns to link bed with being awake and frustrated. Sleep researchers call this conditioning, and it explains why some people feel sleepy on the sofa but wide awake the moment they get into bed.
Health reasons you can’t sleep
8. Hormones: periods, perimenopause and menopause
Some women sleep worse in the days before a period: see insomnia before your period. In perimenopause and menopause, the NHS says not being able to get to sleep or stay asleep is common, and sleep problems may be worse if you also have night sweats. Our perimenopause and sleep guide covers what helps, including HRT and CBT.
9. Pain and other physical conditions
Long-term pain is on the NHS list of insomnia causes, along with an overactive thyroid, and conditions such as Parkinson’s and Alzheimer’s disease. If something physical keeps you awake or wakes you up, getting it treated is often the real sleep fix.
10. Medicines
The NHS notes that many medicines can cause insomnia. If your sleep changed after you started or changed a medicine, ask your pharmacist or GP whether it could be the reason and whether the timing of your dose matters. Don’t stop a prescribed medicine without talking to them first.
11. Mental health
Anxiety tends to make it hard to fall asleep. Depression can do that too, and the NHS also lists waking up very early in the morning as a symptom. Occasionally, not needing much sleep while feeling full of energy can be part of a high mood in bipolar disorder. If your sleep and your mood have both changed, talk to your GP. You can also refer yourself to NHS Talking Therapies for anxiety and depression if you’re 18 or over.
12. Sleep apnoea
In sleep apnoea, your breathing stops and starts while you sleep. The NHS lists loud snoring, gasping or choking noises and waking up a lot, then feeling very tired, struggling to concentrate or waking with a headache during the day. It can be serious if it’s not treated, so see a GP. Read sleep apnoea symptoms and tests.
13. Restless legs syndrome
Restless legs syndrome causes a strong urge to move your legs, with tingling, throbbing or itching, and the NHS says it’s usually worse at night when you’re resting. It’s linked to iron deficiency anaemia and pregnancy. See a GP if it’s stopping you sleeping. More in our restless legs guide.
14. A body clock that runs late (or early)
Some people’s body clock is simply set later than their alarm allows. They can’t fall asleep until 1 or 2am but sleep well if they’re allowed to wake late. Others run early and wake at dawn. These circadian rhythm problems often improve with a fixed wake time and morning light, which our sleep schedule guide covers. If not, a GP can refer you to a sleep clinic.
What to do tonight if you can’t sleep
- Stop watching the clock. Turn it round or put your phone out of reach. Counting the hours left only adds pressure.
- Get up after about 20 minutes. This is NHS advice: if you’re still awake after around 20 minutes, get up and sit somewhere comfortable, do something calm such as reading a paper book or listening to quiet music in dim light, and go back to bed when you feel sleepy.
- Park your worries. Write down tomorrow’s to-do list or whatever is on your mind, so your brain doesn’t have to hold it.
- Slow your breathing. Breathe out for longer than you breathe in. Our fall asleep fast guide has the military method and other techniques.
- Don’t try to make up for it. Get up at your normal time tomorrow, even after a bad night, and skip the nap. That builds the sleep pressure that helps tomorrow night.
Remember: one bad night feels awful, but it doesn’t mean you have insomnia. The NHS describes insomnia as regularly having problems sleeping, and sleeplessness linked to a short-term stress often settles once the stress passes.
What to change this week
- Fix your wake time. Same time every day, weekends included. Go to bed only when you’re sleepy.
- Set a caffeine cut-off of about 6 hours before bed, and keep alcohol and cigarettes out of that window too.
- Build a wind-down hour. Dim lights, screens away, something calm. Our 60-minute bedtime routine gives you a plan.
- Move during the day. The NHS advises regular exercise, but not in the 4 hours before bed.
- Make your bedroom for sleep: cool, dark, quiet, and no work or scrolling in bed.
- Eat earlier. The NHS advises against a large meal late at night.
- Keep a simple sleep diary for 1 to 2 weeks: bedtime, wake time, caffeine, alcohol and how you felt. It shows up patterns and is useful to take to a GP appointment.
For the full list of habits, see our sleep hygiene guide.
If a warm drink is part of your wind-down, our Magnesium Glycinate Sleep Complex is a caffeine-free berry drink made with magnesium bisglycinate and citrate, glycine, L-theanine and chamomile. Magnesium contributes to a reduction of tiredness and fatigue and to normal psychological function. To be clear, it isn’t a sleeping aid or a treatment for insomnia, and NICE’s guidance for GPs doesn’t recommend over-the-counter remedies for insomnia, so the habits above come first. We don’t recommend our products during pregnancy or breastfeeding, and they’re for adults only.
CBT-I: the first-line treatment for long-term insomnia
If you’ve struggled to sleep for weeks or months, the treatment with the best evidence isn’t a pill. It’s cognitive behavioural therapy for insomnia (CBT-I), a short, structured programme that retrains the habits and thoughts keeping you awake. It usually includes a fixed wake time, only going to bed when sleepy, getting up when you can’t sleep, a temporary limit on time in bed (sleep restriction), and work on worries about sleep.
NICE’s guidance for GPs says that when sleep hygiene hasn’t worked and insomnia is unlikely to settle soon, people should be offered CBT-I, face to face or digitally. Sleeping pills are only for short courses, ideally under a week and no longer than 2 weeks. NICE also recommends one digital CBT-I programme for use in primary care for people who would otherwise be offered sleep hygiene advice or sleeping pills.
The results are real. A review of 20 trials found that CBT-I helped people fall asleep about 19 minutes faster and cut time awake in the night by about 26 minutes, with benefits that seemed to last. In a trial of 1,711 people with insomnia symptoms, run by researchers who included the programme’s developers, digital CBT-I improved sleep-related quality of life much more than sleep hygiene education alone.
Ask your GP what’s available locally, as access to face-to-face CBT-I varies. Our insomnia guide explains how CBT-I works step by step.
When to see a GP
The NHS says to see a GP if:
- changing your sleeping habits hasn’t helped
- you’ve had trouble sleeping for months
- your insomnia is affecting your daily life and how you cope
Also see a GP if someone has noticed you stop breathing or gasp in your sleep, you’re very sleepy in the day, your legs won’t settle at night, or your sleep changed after starting a medicine. Don’t drive if you feel sleepy. If you’re pregnant and sleeping badly, talk to your midwife or GP before taking any remedy or supplement.
Need help now? If you can’t sleep because you feel unsafe, hopeless or in crisis, call NHS 111 and select the mental health option, or call Samaritans free on 116 123. If your life or someone else’s is at risk, call 999 or go to A&E.
FAQs
Why can’t I sleep even when I’m tired?
Being tired and being ready to sleep aren’t the same. Stress, late caffeine, evening screens or worry about sleep can keep your brain alert even when your body is exhausted. If it happens most nights, your brain may have learned to link bed with being awake.
Why can’t I sleep all of a sudden?
Think about what changed recently: a stressful event, a new medicine, more caffeine or alcohol, a new schedule, illness or hormone changes. Short-term sleeplessness often settles once the trigger passes. If it lasts more than a few weeks, see a GP.
What should I do if I haven’t slept for 2 or 3 days?
Keep a normal wake time, avoid naps, caffeine and alcohol, and don’t drive if you feel sleepy. See a GP if it carries on or is affecting how you cope. If you also feel unusually high, agitated, confused or unsafe, get urgent help from NHS 111 or call 999 in an emergency.
Why can I sleep during the day but not at night?
Usually your body clock has shifted later, often after late nights, shift work or long naps. Daytime naps also use up the sleep pressure you need at night. A fixed wake time and morning daylight help reset it.
Is it better to stay in bed and rest if I can’t sleep?
Not for long. The NHS advises getting up if you’re still awake after about 20 minutes and doing something calm until you feel sleepy. Lying awake in bed can train your brain to link bed with being awake.
What is the best treatment if I can’t sleep for months?
CBT for insomnia (CBT-I) is the first-line treatment for long-term insomnia, and NICE says it can be offered face to face or digitally. Sleeping pills are only used for short courses. Ask your GP what’s available locally.
Sources
- NHS. Insomnia.
- NHS Every Mind Matters. How to fall asleep faster and sleep better.
- NICE Clinical Knowledge Summaries. Insomnia: managing insomnia (revised June 2026).
- NICE. HealthTech guidance HTG624 (formerly MTG70): digital CBT-I for insomnia.
- NHS. Sleep apnoea and Restless legs syndrome.
- NHS. Menopause symptoms and Depression symptoms.
- Trauer JM et al. (2015). Cognitive behavioral therapy for chronic insomnia: a systematic review and meta-analysis. Annals of Internal Medicine.
- Espie CA et al. (2019). Effect of digital CBT for insomnia on health, psychological well-being, and sleep-related quality of life. JAMA Psychiatry.
- Drake C et al. (2013). Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. Journal of Clinical Sleep Medicine.
- Chang AM et al. (2015). Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. PNAS.
- Ebrahim IO et al. (2013). Alcohol and sleep I: effects on normal sleep. Alcoholism: Clinical and Experimental Research.
- Okamoto-Mizuno K, Mizuno K (2012). Effects of thermal environment on sleep and circadian rhythm. Journal of Physiological Anthropology.
- Ohayon MM (2002). Epidemiology of insomnia: what we know and what we still need to learn. Sleep Medicine Reviews.
- Spielman AJ et al. (1987). A behavioral perspective on insomnia treatment. Psychiatric Clinics of North America.
This guide is general information, not medical advice. Evopure makes the Magnesium Glycinate Sleep Complex.
