If you live in the UK, Vitamin D is something most of us need to think about — especially from autumn through to early spring.
Vitamin D is often called the “sunshine vitamin,” but it’s actually a hormone your body makes when your skin is exposed to ultraviolet B (UVB) light from the sun. In the UK, the sun is only strong enough for this when the UV index is 3 or above, which usually happens in the warmer months.
That means that for much of the year, our bodies can’t make Vitamin D naturally — even on bright, sunny days. This is normal at northern latitudes, but it does mean deficiency is common and often overlooked.
This guide explains:
- When and how Vitamin D is made
- Why deficiency is so common in the UK
- How to support healthy levels safely and simply
- How Vitamin D fits into a wider picture of seasonal wellbeing and light exposure
It’s designed to inform and reassure, not to overwhelm or tell you what to do.
Vitamin D: Nourishing your inner sunshine
Vitamin D It plays an important role in mood, energy, immunity, muscle and bone health, and overall resilience.
In the UK, Vitamin D is one of the most common nutrient deficiencies, especially in autumn and winter. Understanding how it works and how to support it can make winter feel noticeably more manageable.
How your body makes Vitamin D
Your body can only make Vitamin D through your skin when ultraviolet B (UVB) rays from the sun are strong enough. This happens when the UV index is 3 or above.
In the UK, that typically means:
- Late March/April to September (depending on weather, time of day, and location)
- Usually around the middle of the day
- Not early morning, late afternoon, or through windows
- Sunlight through glass does not allow Vitamin D production, because UVB rays are filtered out.
From roughly October to early spring, the sun in the UK simply isn’t strong enough for Vitamin D production, even on bright, sunny days. This is normal and expected at our latitude.
Why Vitamin D matters in winter
Vitamin D supports many systems in the body, including:
- Mood and emotional wellbeing
- Energy levels and fatigue
- Immune function
- Muscle strength and bone health
Low Vitamin D doesn’t automatically cause low mood or winter struggles, but it can amplify how hard winter feels, especially alongside seasonal light changes or existing health conditions.
Addressing Vitamin D is often one of the simplest ways to reduce unnecessary strain on your system.
Sun exposure: awareness, not pressure
Sun exposure has been used for health and wellbeing for centuries, and modern science is still uncovering its wide-ranging benefits beyond Vitamin D alone.
That said, how (or whether) you choose to get sunlight is a personal decision.
Some people:
- Prefer short, sensible periods of sun exposure in summer
- Are cautious due to skin type, medication, or health history
- Have personal or family experiences of skin cancer
- Choose to stay covered or use sunscreen at all times
All of these choices are valid.
The key point is awareness:
- Vitamin D stores will gradually run down if they aren’t replenished
- In UK winter, this can’t happen naturally through sunlight
- Supplementation is a safe, widely recommended alternative
Supplementing Vitamin D
Because of our climate, UK public health guidance recommends that adults and children consider taking a daily Vitamin D supplement, particularly during autumn and winter.
Supplementing:
- Helps maintain healthy Vitamin D levels when sunlight isn’t sufficient
- Is especially important if you get little outdoor sun exposure year-round
- Can be a simple, low-effort “quick win” for winter wellbeing
If you’re unsure what’s right for you, or if you have existing health conditions, a healthcare professional can provide personalised advice.
Small choices that support Vitamin D
You don’t need to do everything. Even one small, consistent action helps.
You might choose to:
- Take a daily supplement during autumn and winter
- Pair your supplement with a meal containing healthy fats to aid absorption
- Use a UV index or Vitamin D app to build awareness and plan when you might go outdoors and how long for
- Enjoy outdoor daylight when conditions allow, in ways that feel safe for you
Consistency matters far more than perfection.
Learn more
If you’d like to explore Vitamin D further, these trusted resources offer different perspectives – from official UK guidance to specialist research and practical tools. All are optional.
Official UK guidance
NHS – Vitamin D: Clear, accessible information on why Vitamin D matters, who may be at risk of deficiency, and current UK recommendations on supplementation.
Making Vitamin D safely from sunlight
GrassrootsHealth – How to Make Vitamin D from Sunshine: Practical guidance on how Vitamin D is made in the skin, the role of the UV index (≥3), and how to approach sun exposure with awareness and care.
Deeper dives & alternative perspectives
Defend Your Life II – Susan Rex Ryan: Explores Vitamin D research, testing, and supplementation in more depth. Includes suggested protocols and access to a supportive online community for those who want to go further.
Please note: Vitamin D supplementation and sun safety can be contentious topics. We intentionally share both official guidance and specialist perspectives so you can read broadly and decide what feels right for you.
Helpful tools
dminder app (iOS & Android): Helps you understand when UV levels are high enough to make Vitamin D, track sun exposure safely, and set reminders for supplementation if you choose.
A gentle reminder
Winter at northern latitudes places real demands on the body. Supporting your Vitamin D levels – as with all light nutrition tactics – is about working with your biology, not against it. Sometimes, feeling brighter starts with the smallest tweaks.
These resources are provided for information and learning, not as medical advice. Everyone’s body, history and circumstances are different – you’re always free to take what’s useful and leave the rest.
Next steps…
- Read more about light nutrition.
- If you’re interested in a more holistic, seasonal approach to wellbeing, you may also like Bright in Winter – a gentle programme exploring light, rhythm, and energy through the darker months.