Why Am I Always Tired? Winter Fatigue, Low Vitamin D & Causes
By Dr Daniel Gordon • 03, Apr 2026
Feeling unusually tired as winter comes to an end is common. Many people notice low energy, reduced motivation, and difficulty concentrating during late winter and early spring.
This isn’t random. Reduced sunlight, changes in routine, and lower vitamin D levels all contribute. In some cases, fatigue is temporary. In others, it may signal something that needs attention.
This guide explains the most common causes, what symptoms to look for, and what you can do to improve your energy levels.
Why You Feel Tired at the End of Winter
During winter, your body is exposed to less natural light. This affects your internal clock, hormone levels, and overall energy balance.
At the same time, lifestyle habits often shift. People tend to exercise less, spend more time indoors, and change eating patterns. These small changes build up over time and can leave you feeling persistently tired.
As winter ends, your body is still adjusting. That’s why fatigue often peaks just before spring fully arrives.
Symptoms of End-of-Winter Fatigue
Common signs of low energy
Ongoing tiredness despite getting enough sleep
Low motivation or lack of drive
Difficulty concentrating or “brain fog”
Low mood or irritability
Feeling physically sluggish
These symptoms tend to develop gradually and may last for several weeks.
Common Causes of Fatigue at the End of Winter
Fatigue is rarely caused by one single factor. It is usually a combination of biological and lifestyle influences.
Low Vitamin D and fatigue
Vitamin D is mainly produced through sunlight exposure. During winter months, levels often drop.
Low vitamin D can affect:
Energy levels
Muscle strength
Immune function
Mood
Common signs include fatigue, muscle aches, and increased susceptibility to infections.
In the UK, low vitamin D levels are particularly common from October to early spring.
Reduced sunlight and disrupted sleep cycle
Less daylight affects your circadian rhythm, which controls your sleep-wake cycle.
This can lead to:
Increased daytime tiredness
Difficulty waking up
Changes in sleep quality
Your body may produce more melatonin, making you feel more sleepy than usual.
Poor sleep quality
Even if you are sleeping enough hours, the quality of sleep may be reduced.
Common contributing factors:
Irregular sleep patterns
Increased screen use in the evening
Stress or disrupted routines
Poor sleep quality often leads to ongoing fatigue during the day.
Seasonal low mood and energy levels
Some people experience a noticeable drop in mood during winter months.
This can result in:
Reduced motivation
Low energy
Difficulty focusing
Even mild seasonal changes in mood can affect how energised you feel.
Diet, activity levels and winter habits
Winter routines often include:
Less physical activity
Heavier or less balanced meals
Reduced exposure to fresh air
These factors can contribute to feeling sluggish and low in energy.
How to Check the Cause of Persistent Fatigue
If fatigue continues or feels excessive, it is important to identify the underlying cause.
What a GP may assess
Sleep patterns and daily routine
Diet and activity levels
Stress and mental wellbeing
Medical history
Tests for fatigue and low energy
A GP may recommend blood tests to check:
Vitamin D levels
Iron levels (to rule out anaemia)
Thyroid function
This helps determine whether there is a specific medical reason for fatigue.
How to Boost Energy Levels After Winter
Improving energy often involves small, consistent changes.
Increase daylight exposure
Spend time outdoors during daylight hours
Let natural light into your home early in the day
Vitamin D supplements
Supplements are commonly recommended during autumn and winter
Speak to a pharmacist or GP for guidance if needed
Improve sleep routine
Keep consistent sleep and wake times
Reduce screen exposure before bed
Stay active
Regular movement supports energy and mood
Even light activity such as walking can help
Improve diet
Focus on balanced meals
Include fresh foods, fruit, and vegetables
Manage stress
Take breaks during the day
Use relaxation techniques where needed
These steps can help restore energy levels over time.
When to See a GP for Ongoing Fatigue
Seek medical advice if
Fatigue lasts for several weeks without improvement
It is affecting daily life or work
You have additional symptoms such as dizziness, weight changes, or shortness of breath
You are unsure of the cause
Urgent symptoms to watch for
Severe or worsening fatigue with other unexplained symptoms
Persistent shortness of breath
Chest pain or fainting
These symptoms require prompt medical attention.
The Bottom Line on Winter Fatigue
Feeling tired at the end of winter is common and often linked to reduced sunlight, low vitamin D, and lifestyle changes. For many people, energy levels improve naturally as spring progresses. If fatigue continues or worsens, identifying the cause and taking targeted steps can help you recover more effectively.
Disclaimer
This blog post provides general information only. It is not intended to provide instruction and you should not rely on this information to determine a diagnosis, prognosis or course of treatment. It should not be used in place of a professional consultation with a doctor.
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