Why Vitamin D Is Essential
Vitamin D isn't just a vitamin — it's actually a hormone that affects virtually every cell in your body. It plays a crucial role in:
- Bone health — Helps your body absorb calcium
- Immune function — Supports your body's defence against infections
- Mood regulation — Low levels are linked to depression and seasonal affective disorder (SAD)
- Muscle function — Deficiency can cause weakness and aches
- Heart health — Emerging research suggests a protective role
Understanding Your Levels
| Level (nmol/L) | Status |
|---|---|
| Below 25 | Deficient — treatment needed |
| 25 – 50 | Insufficient — supplementation recommended |
| 50 – 80 | Adequate |
| 80 – 150 | Optimal |
| Above 375 | Potentially toxic |
Who's at Risk?
- Anyone living above 37° latitude — Including the entire UK, where UV is too weak for vitamin D production from October to March
- People with darker skin — Melanin reduces vitamin D synthesis
- Indoor workers — Office workers, shift workers
- Older adults — Skin becomes less efficient at producing vitamin D with age
- People who cover up — Whether for cultural, religious, or sun-protection reasons
- Overweight individuals — Vitamin D gets trapped in fat tissue
Symptoms of Deficiency
- Fatigue and tiredness
- Bone pain and back pain
- Frequent illness or infections
- Low mood, especially in winter
- Slow wound healing
- Muscle weakness
- Hair loss
How to Get More Vitamin D
Sunlight
- 10–20 minutes of midday sun on bare arms and face (without sunscreen) during summer months
- This isn't possible in the UK from October to March
Supplements
- NHS recommendation: Everyone should consider taking 10 µg (400 IU) daily in autumn and winter
- If deficient: Your GP may prescribe higher doses (800–4000 IU daily)
- Vitamin D3 (cholecalciferol) is more effective than D2
- Take with a meal containing fat for better absorption
Food Sources
- Oily fish (salmon, mackerel, sardines)
- Egg yolks
- Fortified foods (cereals, milk, plant milks)
- Mushrooms exposed to UV light
Track Your Vitamin D
Vitamin D is one of the most commonly tracked biomarkers on CheckMyBloods. Upload your results to see how your levels change with the seasons, track the effect of supplementation, and get personalised insights from your AI health assistant.
