Winter Fatigue: Causes and Ways to Manage It

• 10 December 2024, by SANUSq Research team
• 13 min reading time

The mornings are dark, the evenings arrive mid-afternoon, and your energy seems to have gone into hibernation. Winter fatigue is so common that most of us shrug it off as part of the season. Yet it usually has identifiable causes, several of which you can do something about.

Written by SANUSq Research Team | Medically reviewed by Dr Ajay Kumar, MD
Published: 10 December 2024 | Updated: 10 December 2024

Why winter fatigue happens

Tiredness in winter is rarely down to one thing. Less daylight, a body clock that drifts, lower vitamin D status, less movement and a steady run of colds tend to stack up together.

Some causes, though, have nothing to do with the season and simply become more noticeable when everything else is harder. Iron deficiency and an underactive thyroid are two of the most common. It helps to look at each in turn.

Less daylight and a drifting body clock

Your internal clock, or circadian rhythm, is set mainly by light, and morning light is the strongest signal of all. In winter we wake in the dark, travel in the dark and spend most of the day under indoor lighting, which is far dimmer than daylight even on an overcast day. The result is a clock that runs later than the day you're trying to live, so you can feel awake without feeling properly alert.

Low vitamin D in the darker months

Most of our vitamin D is made in the skin in response to sunlight. At northern European latitudes, the winter sun sits too low for the skin to make much, so blood levels tend to fall through the season. People who spend little time outdoors, older adults, people with darker skin and people with a higher body weight are especially likely to run low.

Vitamin D contributes to the normal function of the immune system and to the maintenance of normal muscle function. It is not, however, one of the nutrients authorised to claim a role in reducing tiredness, so low vitamin D shouldn't be assumed to be the reason you feel drained.

Moving less

Cold, wet weather and dark evenings cut activity for almost everyone. That matters, because one of the best-established findings about fatigue runs against intuition: regular movement tends to increase energy, while resting more usually doesn't.

Winter infections

Colds, flu and other respiratory infections peak in winter, and the tiredness that follows them can last longer than the sniffles.

Iron deficiency

Iron deficiency is one of the most common nutritional shortfalls worldwide, particularly in women who menstruate, during pregnancy, in people who eat little or no meat and in regular blood donors. Iron contributes to normal formation of red blood cells and haemoglobin and to the reduction of tiredness and fatigue. Importantly, you can be low in iron stores without being anaemic.

Because too much iron can be harmful, iron is best taken when a blood test (including ferritin) shows you need it, and under your doctor's guidance.

An underactive thyroid

The thyroid sets the pace of your metabolism. When it produces too little hormone, the result can look a lot like winter: tiredness, sluggishness, feeling the cold more than others, weight gain, constipation and dry skin. Because these symptoms overlap with the season, hypothyroidism can be missed for a long time.

A simple blood test can rule it in or out. Supplements are not a substitute for medical care of thyroid disease.

Low mood that returns every winter

For some people, winter brings more than low energy: a persistently low mood, loss of interest, oversleeping and strong carbohydrate cravings that come back each year and lift in spring. This is seasonal affective disorder (SAD), a recognised form of depression that responds to treatment. We cover it, and light therapy, in our article on seasonal affective disorder. If this sounds like you, speak to your GP rather than reaching for a supplement.

Winter fatigue remedies: what actually helps

The most effective steps cost nothing, and they target the causes rather than masking the symptoms.

1. Get outside in the morning. Fifteen to thirty minutes of daylight early in the day, even under grey skies, gives your body clock a much stronger signal than an hour beside a window.
2. Keep a steady wake-up time. Getting up at the same time every day, weekends included, helps anchor your rhythm. Dimming screens and lights in the evening helps you fall asleep on time.
3. Move every day. A brisk 30-minute walk in daylight combines two of the best levers at once. Consistency matters more than intensity; the aim is to avoid letting winter turn into weeks of inactivity.
4. Eat for steady energy. Sugary snacks give a quick lift and a slump. Wholegrains, pulses, vegetables and some protein at each meal keep energy more even through the day.
5. Go easy on caffeine and "energy" drinks. They can borrow energy from later in the day and, taken late, cost you sleep the following night.

Nutrients for tiredness in winter: what the claims allow

Supplements make most sense when they fill a genuine gap, not as a substitute for light, sleep and movement. Within EU rules, the following nutrients are authorised to say they contribute to the reduction of tiredness and fatigue:

• Vitamin C — found in citrus fruit, kiwi, peppers and leafy greens. It also contributes to the normal function of the immune system.
• B vitamins — including B2, B3, B5, B6, B12 and folate, found in wholegrains, eggs, dairy foods, meat, fish, pulses and green vegetables. Vitamin B12 is worth particular attention if you eat a plant-based diet.
• Iron — from red meat, pulses, tofu and fortified cereals, ideally eaten with a source of vitamin C. Supplements only after testing.
• Magnesium — from nuts, seeds, wholegrains and leafy greens. It also contributes to normal energy-yielding metabolism.

Vitamin D is a different case. Its role is in normal immune function, normal muscle function and the maintenance of normal bones, which is why many health authorities suggest considering it during the darker months, especially if you rarely get outdoors. It has no authorised claim for tiredness.

If you choose a vitamin D product that also contains vitamin K2, such as our Liposomal Vitamin D3 + K2, bear in mind that vitamin K contributes to normal blood clotting. If you take warfarin or another vitamin K antagonist blood thinner, speak to your doctor before starting any product containing vitamin K.

When tiredness in winter needs a doctor

No supplement makes up for too little sleep, and none deals with a medical cause. See your doctor if your tiredness:

• lasts more than a few weeks, or keeps getting worse
• comes with breathlessness, palpitations, unexplained weight loss, fever or night sweats
• comes with heavy periods, very pale skin or feeling unusually cold
• is accompanied by low mood, loss of interest or thoughts of hopelessness
• comes with loud snoring or pauses in breathing at night, which can point to sleep apnoea

Common, treatable causes such as anaemia, an underactive thyroid, sleep apnoea and depression are usually picked up with a conversation and a few blood tests.

The bottom line

Winter fatigue usually comes from several small things adding up: less light, a later body clock, less movement and more infections. In order of priority, get morning daylight, keep regular sleep hours, stay active, eat for steady energy and keep an eye on your vitamin D through the dark months. Supplements can support that where there is a real shortfall. And if the tiredness won't lift, a check-up beats another box from the shelf.

Frequently asked questions

Why am I so tired in winter?

Less morning light shifts your body clock later, you probably move less, your vitamin D levels fall without enough sun, and winter infections are more frequent. These factors tend to combine. If tiredness persists, iron deficiency and thyroid problems are worth ruling out.

What are the best natural winter fatigue remedies?

Morning daylight, a regular wake-up time and daily physical activity are the most effective steps, because they address the causes of low energy rather than masking it. A balanced diet helps too.

Which vitamins help with tiredness?

Vitamin C, several B vitamins, iron and magnesium contribute to the reduction of tiredness and fatigue. Iron should only be supplemented when a blood test shows you need it.

Does vitamin D help with winter tiredness?

Vitamin D contributes to normal immune function and normal muscle function, and levels commonly drop in winter. It is not authorised to claim a role in reducing tiredness, so if fatigue is your main concern, look at sleep, light, activity, iron and thyroid function as well.

Is winter fatigue the same as seasonal affective disorder?

No. Seasonal affective disorder is a form of depression, with low mood, loss of interest, oversleeping and carbohydrate cravings that return every winter. It needs medical support, so talk to your GP if this sounds familiar.

When should I see a doctor about tiredness?

If it lasts more than a few weeks, gets worse, or comes with breathlessness, weight loss, fever, heavy periods or persistently low mood. Many common causes are easy to identify and manage once diagnosed.

References

1. Stothard ER, McHill AW, Depner CM, et al. Circadian entrainment to the natural light-dark cycle across seasons and the weekend. Current Biology. 2017;27(4):508–513. PMID 28162893
2. Cashman KD, Dowling KG, Škrabáková Z, et al. Vitamin D deficiency in Europe: pandemic? American Journal of Clinical Nutrition. 2016;103(4):1033–1044. PMID 26864360
3. Puetz TW, O'Connor PJ, Dishman RK. Effects of chronic exercise on feelings of energy and fatigue: a quantitative synthesis. Psychological Bulletin. 2006;132(6):866–876. PMID 17073524
4. Martineau AR, Jolliffe DA, Hooper RL, et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ. 2017;356:i6583. PMID 28202713
5. Houston BL, Hurrie D, Graham J, et al. Efficacy of iron supplementation on fatigue and physical capacity in non-anaemic iron-deficient adults: a systematic review of randomised controlled trials. BMJ Open. 2018;8(4):e019240. PMID 29626044
6. Chaker L, Bianco AC, Jonklaas J, Peeters RP. Hypothyroidism. Lancet. 2017;390(10101):1550–1562. PMID 28336049

Read more on the blog

• Top Causes of Unexplained Fatigue →
• Magnesium and Tiredness: Why Low Magnesium Can Leave You Running on Empty →
• Vitamin D in Winter: Benefits, Deficiency, and How to Get Enough →

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Explore more on our channel, @SANUSqHealthSupplements.

We wish you good health on your terms.
The team at SANUSq.

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