Why you feel tired in winter and how to get your energy back
Winter tiredness is extremely common in the UK, and it often comes down to a combination of biology, light exposure, vitamin changes, and lifestyle shifts. The good news is that winter fatigue is manageable once you understand what causes it - and the steps you can take to get your energy back.
As daylight drops, many people notice slower mornings, mid-afternoon slumps, carb cravings, or feeling unusually sleepy. These changes are natural responses to reduced sunlight and seasonal rhythms. This article breaks down what is happening inside your body, why winter affects energy so strongly, and how to feel more alert, motivated, and balanced even on the darkest days.
Why you feel tired in winter
Winter tiredness has nothing to do with willpower. When daylight decreases, your internal body clock - called the circadian rhythm - starts to shift. Your brain uses sunlight to regulate melatonin (the hormone that makes you sleepy) and serotonin (which helps regulate mood and energy). Reduced light exposure increases melatonin during the day, which can leave you - feeling flat, foggy, or unusually tired.
The NHS highlights that reduced sunlight in winter can disrupt this rhythm and contribute to low energy, sluggishness, and mood changes. Increased melatonin during winter months plays a major role in daytime tiredness and lethargy.
Typical winter-related symptoms include:
• Struggling to wake up, even after a full night’s sleep
• Feeling sleepy or unfocused during the day
• Craving carbohydrates or comfort foods
• Feeling less motivated or less productive
• Wanting to sleep earlier or sleep longer
These symptoms are extremely common during darker months, and they often appear gradually across late autumn and winter.
Low energy in winter: How daylight affects your body
Light exposure is one of your body’s strongest regulators for wakefulness and alertness. When sunlight is scarce, particularly in the UK between October and March, your brain receives fewer “wake-up” signals. This can lead to daytime sleepiness, poorer concentration, and reduced motivation.
Lack of sunlight can disrupt serotonin levels, contributing to tiredness, low mood, and difficulty focusing. Even cloudy daylight offers significantly more brightness than indoor lighting, which is why outdoor exposure - even for short periods - can noticeably impact energy.
Morning light is especially powerful. Light exposure early in the day helps “reset” your body clock and decreases melatonin production, supporting better alertness.
Winter tiredness and vitamin D levels
Vitamin D plays a key role in muscle function, mood, and overall wellbeing - and it drops sharply in winter. The NHS states that UK sunlight is not strong enough for vitamin D production between October and March, making deficiency more likely during winter months.
The NHS recommends that everyone in the UK take a daily vitamin D supplement during autumn and winter because the sun simply isn’t strong enough for your skin to produce it naturally. Even people who spend time outdoors won’t make meaningful amounts of vitamin D between October and March. Low levels are strongly linked with tiredness, muscle weakness, low mood, and feeling “run down,” which is why many people notice their energy dipping during the darker months. A simple at-home test can help you understand whether vitamin D deficiency is contributing to your symptoms, giving you clarity on whether supplementation or lifestyle adjustments could support your energy more effectively.
Because vitamin D deficiency can be subtle, many people attribute the effects to general winter tiredness without realising their levels have fallen. Testing can help identify whether vitamin D is influencing your energy, especially if tiredness becomes persistent.
How winter impacts sleep quality
Even if your sleep duration stays the same, winter can affect sleep quality. When it stays dark late into the morning, your natural cues for waking are delayed. Earlier sunsets can also make you feel sleepy too soon, leading to irregular sleep patterns.
Common winter sleep disruptions include:
• More broken sleep
• Waking up groggy
• Oversleeping but still feeling tired
• Trouble feeling fully awake
• Falling asleep earlier than usual
NHS guidance notes that irregular light exposure which disrupts your circadian rhythm contributes to these changes. A consistent routine can help stabilise your sleep-wake cycle.
Winter tiredness and mood: Understanding the connection
Seasonal shifts affect mood as well as energy. Reduced sunlight lowers serotonin production, which can affect motivation, emotional balance, and mental clarity. Some people experience the “winter blues,” while others may notice stronger emotional shifts in the darker months.
NHS England highlights that low motivation, sluggishness, and “winter blues” are common when daily structure and sunlight decrease. Supporting your mood is an essential part of improving winter energy.
Nutrition for better energy during winter
When you are tired, comfort foods feel appealing - especially carb-heavy meals. However, these can cause quick rises and drops in blood sugar, leading to more fatigue. The British Dietetic Association notes that balanced meals and stable blood glucose help maintain steady energy and prevent crashes.
Energy-supporting foods include:
• Whole grains such as oats, brown rice, and wholemeal bread
• Lean proteins like eggs, poultry, legumes, and tofu
• Healthy fats such as olive oil, nuts, and seeds
• Fruits and vegetables for vitamins, minerals, and antioxidants
Hydration also matters. Many people drink less water in winter because they feel less thirsty, but dehydration contributes to headaches, tiredness, and poor concentration.
Winter tiredness: Proven ways to boost energy
1. Get outside within the first few hours of waking
Morning light helps regulate melatonin and boost alertness, even on overcast days.
2. Keep a consistent sleep schedule
Going to sleep and waking at the same time each day helps stabilise your body clock.
3. Eat balanced meals to stabilise energy
Skipping meals or relying on sugary foods leads to energy crashes. Focus on whole grains, lean proteins, and healthy fats.
4. Stay active, even gently
Regular movement boosts circulation, supports mood, and improves sleep - all essential for winter energy.
5. Supplement vitamin D if needed
The NHS recommends daily vitamin D supplements in winter because sunlight is insufficient for natural production. Testing can help confirm if low levels are contributing to tiredness.
When winter tiredness may need closer attention
Winter tiredness usually improves with light exposure, better sleep routines, and balanced nutrition. But if your energy levels stay low for several weeks, or if tiredness affects daily life, it may be helpful to check what is happening internally.
Nutrient deficiencies, thyroid changes, and fluctuating vitamin D levels can all contribute to persistent fatigue. At-home testing offers an accessible way to understand your energy on a deeper level.
The role of at-home testing
If you have been feeling unusually tired for several weeks, if your energy does not improve with lifestyle changes, or if your symptoms are affecting daily life, it’s sensible to speak with your GP. At-home testing can also help you understand whether nutrient or vitamin levels may be contributing to how you feel.
MyHealthChecked’s Energy Profile Blood Test assesses biomarkers commonly linked to fatigue. It includes a full blood count, kidney function, liver function, ferritin (iron), total bilirubin, folate, vitamin D, active vitamin B12, and thyroid-stimulating hormone (TSH). These markers can help identify potential contributors to low energy, such as vitamin deficiencies, anaemia, or thyroid-related issues. The test also provides GP-reviewed recommendations with clear next steps based on your results.
MyHealthChecked’s Vitamin D Rapid Test is a simple finger-prick test that provides results in around 10 minutes. It indicates whether your vitamin D levels are sufficient (>30 ng/ml), insufficient (10–30 ng/ml), or deficient (<10 ng/ml). The report includes doctor-led guidance on what your result means and what you may wish to do next.
Using at-home tests can help you understand whether winter tiredness is related to seasonal changes alone or whether nutrient levels or other biomarkers may also be playing a role.
Frequently asked questions
1. Why do I feel tired all winter?
Shorter daylight disrupts the body's production of melatonin and serotonin, affecting alertness and mood. Low vitamin D can also contribute to tiredness.
2. How can I boost my energy in winter?
Morning daylight, balanced meals, hydration, gentle exercise, and consistent sleep help to boost energy. Light therapy may also support daytime alertness.
3. Does vitamin D affect energy levels?
Yes. Low vitamin D is linked to low energy, muscle weakness, and mood changes. Levels typically fall in UK winter.
4. Why do I crave carbs in winter?
Reduced serotonin from lower daylight can increase cravings for carbohydrate-rich foods, which temporarily lift mood.
5. Should I get tested for winter tiredness?
Testing can help identify nutrient deficiencies, thyroid issues, or low vitamin D if fatigue persists despite lifestyle changes.
In summary
Winter tiredness is common, and it often stems from reduced sunlight, changes in sleep rhythms, shifts in mood-regulating hormones, and lower vitamin D levels. The good news is that practical habits - morning light, consistent routines, balanced meals, hydration, movement, and checking your vitamin D or energy markers - can help you feel more awake and energised. Understanding what your body needs during the darker months helps you take simple steps toward better energy, clearer mornings, and brighter days ahead.
References
1. NHS. Vitamin D. 2020. https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d/
2. Mayo Clinic. Seasonal affective disorder (SAD) - Symptoms and causes. 2021. https://www.mayoclinic.org/diseases-conditions/seasonal-affective-disorder/symptoms-causes/syc-20364651.
3. Harvard Health Publishing. Shining a light on winter depression. 2024. https://www.health.harvard.edu/newsletter_article/shining-a-light-on-winter-depression.
4. NHS. Seasonal affective disorder (SAD) - Overview. 2022. https://www.nhs.uk/mental-health/conditions/seasonal-affective-disorder-sad/overview/.