Last updated: 31 October 2026. Written by DELIM, a UK sleep wellness brand.
Short answer: Most people feel more tired in winter because there is less daylight. Less light can shift your body clock and change brain chemicals like melatonin and serotonin, which affect mood and sleep. Shorter days also mean less time outside, less movement and, from October to March, not enough sunlight for your skin to make vitamin D.
Feeling a bit slower when the clocks go back is common and usually normal. But if low mood, heavy tiredness or oversleeping come back every winter, it is worth speaking to a GP. This guide explains the main causes, what you can do today, and when to get help.
Is it normal to feel more tired in winter?
Yes, a dip in energy in winter is common. The NHS says that many cases of tiredness come from lifestyle factors such as stress, not enough sleep and poor diet, and winter tends to make several of these harder at once. Darker mornings, colder weather and more time indoors all add up.
There is also early evidence that our sleep itself changes with the seasons. A 2023 study in Frontiers in Neuroscience looked at 188 sleep clinic patients in Berlin. It found REM sleep (the dreaming stage of sleep) was about 30 minutes longer in winter than in spring. Total sleep looked up to 60 minutes longer in winter than in summer, but that difference was not statistically significant. The authors say the results need repeating in healthy people before anyone changes sleep advice.
Why does less daylight make you sleepy?
Daylight is the main signal that sets your body clock, also called your circadian rhythm (your internal 24-hour timer for sleep and alertness). The NHS says reduced daylight in winter may change brain chemicals like melatonin and serotonin, which affect your mood and your sleeping patterns. Melatonin is the hormone that helps you feel sleepy at night.
In winter many of us leave home in the dark and get back in the dark. A January 2025 survey by Simba and The Sleep Charity, reported by Stylist, found two thirds of people in the UK get less than three hours of daylight exposure a day. In the same piece, Lisa Artis of The Sleep Charity said morning light is "the single most important ingredient for setting our circadian clock."
The clocks going back also nudges your routine. Our guide on how to protect your sleep when the clocks go back covers that change in more detail.
Can low vitamin D make you tired in winter?
The NHS says that between October and early March we do not make enough vitamin D from sunlight in the UK. Because of this, government advice is that everyone should consider taking a daily supplement containing 10 micrograms of vitamin D during autumn and winter. Vitamin D mainly helps keep bones, teeth and muscles healthy.
A vitamin D supplement is not a cure for tiredness, and tiredness has many possible causes. The NHS vitamin D page also warns adults not to take more than 100 micrograms (4,000 IU) a day, as it could be harmful. If you take other medicines or have a health condition, check with a GP or pharmacist first.
Is it winter tiredness or seasonal affective disorder (SAD)?
Seasonal affective disorder (SAD) is a type of depression that comes and goes with the seasons. The NHS says its main symptom is depression that happens in winter and goes away in summer. Symptoms can include low mood, losing interest in things, eating more, and being more tired and sleeping more than usual.
The NHS says you may be diagnosed with SAD if you have had these symptoms at a particular time of year for 2 years or longer. You can read more on the NHS SAD page. This table may help you think about which side you are on. It is not a diagnosis.
| Usually everyday winter tiredness | Worth speaking to a GP |
|---|---|
| A bit slower in the mornings after the clocks change | Low mood most days that returns every winter |
| Energy picks up after a walk outside or a good night's sleep | Tiredness that rest and sleep do not ease (the NHS calls this fatigue) |
| You still enjoy your usual activities | Losing interest in things you normally enjoy |
| Small changes in appetite | Eating much more, sleeping much more, or feeling hopeless or worthless |
| Improves within a few weeks as you adjust | Symptoms at the same time of year for 2 years or more |
If you ever have thoughts of harming yourself, get help straight away by calling NHS 111, your GP, or 999 in an emergency.
How can I stop feeling so tired in winter?
The best fixes are simple and free: get outside in daylight early, move every day, keep a regular sleep time and watch caffeine and alcohol. These come from NHS advice on SAD and on fighting tiredness. Try them for two to three weeks before judging the results.
Your UK winter energy checklist
- Get daylight every day. The NHS advises getting as much natural daylight as you can and going outside in the daytime every day. A morning walk, even on a cloudy day, counts.
- Walk for 15 minutes. The NHS tiredness tips say even a single 15-minute walk can give you an energy boost. Build up to 2 hours 30 minutes of moderate exercise a week.
- Keep the same sleep and wake times. The NHS suggests going to bed and waking up at the same time every day, including weekends.
- Stop caffeine by early afternoon. The NHS says the effects of caffeine can last up to 7 hours.
- Go easy on alcohol. The NHS advises not regularly drinking more than 14 units a week. Our post on alcohol and sleep explains how a nightcap affects rest.
- Eat regularly. The NHS suggests regular meals and healthy snacks every 3 to 4 hours, rather than one big heavy meal.
- Drink water. The NHS notes that sometimes you feel tired simply because you are mildly dehydrated.
- Put the phone down before bed. NHS advice for SAD includes not using smartphones and other devices right before going to bed.
- Consider vitamin D from October to March. 10 micrograms a day, as the NHS advises, and no more than 100 micrograms.
Should I sleep more in winter?
There is no official advice to sleep longer in winter. The Berlin study above hints that sleep may change with the seasons, but it looked at people with sleep problems, and the authors say it needs to be repeated in healthy adults. For now, the safest approach is a regular sleep pattern and enough sleep that you wake feeling rested.
Long daytime naps can make night sleep harder, and the NHS tiredness advice suggests avoiding naps in the day. If you want an interesting look at how people slept through long winter nights in the past, read our true story on first sleep and second sleep.
Can your bedroom make winter tiredness worse?
Yes, a bedroom that is too warm, too stuffy or too bright can make sleep lighter, which leaves you more tired the next day. In winter, the heating and closed windows can make the air feel dry, and colds can block your nose. Small changes to your room often help more than you expect.
- See our guide on whether you should sleep with the heating on for temperature tips.
- If a cold is keeping you up, read how to sleep with a blocked nose.
- Fresh bedding helps a room feel calmer. Here is how often to wash your bed sheets.
If you often wake with a dry mouth, you may be breathing through your mouth at night. Some people use DELIM mouth tape to support nose breathing while they sleep. It is not a treatment for tiredness or any condition. If you have breathing problems, sleep apnoea, or a blocked nose, speak to a GP before trying mouth tape.
When should I see a GP about tiredness in winter?
See a GP if tiredness does not get better with rest and sleep, if it lasts for weeks, or if you think you might have SAD. The NHS also says to see a GP if you have been diagnosed with SAD and treatment is not helping. A GP can check for other causes and talk you through options.
The NHS lists treatments for SAD such as talking therapies and antidepressants. It says light therapy is not usually available on the NHS because there is not enough evidence to tell whether it works, though many people find it helps. The NHS advises speaking to a GP before trying a light box.
Frequently asked questions
Why am I so tired in winter even when I sleep well?
Less daylight can shift your body clock and lower your alertness during the day, even after a full night's sleep. Getting outside in the morning and moving every day often helps. If tiredness does not ease with rest, see a GP.
Does vitamin D help with winter tiredness?
The NHS advises everyone in the UK to consider 10 micrograms of vitamin D a day from autumn to early March, because sunlight is too weak to make enough. It supports bones and muscles, but it is not a proven fix for tiredness. Do not take more than 100 micrograms a day.
Is it normal to want to sleep more in winter?
Many people feel sleepier in winter, and one 2023 study of sleep clinic patients found more REM sleep in winter than in spring. But wanting to sleep much more than usual, along with low mood, can be a sign of SAD. Speak to a GP if this happens every winter.
How do I know if I have SAD or just winter blues?
The NHS says SAD is depression that happens in winter and goes away in summer. It may be diagnosed if symptoms appear at the same time of year for 2 years or more. Only a GP can diagnose it.
Do light boxes work for winter tiredness?
The NHS says there is not enough evidence to tell whether light therapy works, but many people find it helps SAD symptoms. If you try one, the NHS suggests 10,000 lux, UV-free and with a UKCA or CE mark. Speak to a GP first.
The bottom line
Winter tiredness is mostly about light: less daylight, a shifted body clock and less time outside. Morning daylight, a daily walk, regular sleep times and vitamin D from October to March are the simplest steps. For more ideas, read our complete guide to improving sleep quality.
This post is for information only and is not medical advice. If you are worried about tiredness, low mood or your health, please speak to your GP.
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