Vitamin D deficiency
Linked to Vitamin D
Low vitamin D weakens bones and muscles and can affect immunity.
Where it shows on the body
Rotate the figure and click a red marker to see the affected area. Internal organs open a 3D organ model.
Causes
- Little sun exposure
- Darker skin
- Covering skin / sunscreen
- Low dietary intake
- Malabsorption
Symptoms
- Bone pain
- Muscle weakness and aches
- Fatigue
- Frequent infections
- Low mood
What happens if untreated
- Rickets in children
- Osteomalacia and fractures in adults
- Falls in older people
Who is most at risk
- Older adults
- People with limited sun exposure
- Darker-skinned individuals
- Breastfed infants
Prevention & sources
- Sensible sun exposure
- Oily fish and fortified foods
- Winter supplements (10 µg+)
Correcting it: foods, amounts & timing
Foods that help & safe amounts
- Oily fish (salmon, mackerel, sardines) — 1–2 portions a week
- Eggs and fortified foods most days
- 10–15 minutes of midday sun on skin in summer
- Supplement of 10 µg (400 IU)/day for most adults; higher short courses only if advised (adult upper limit ~100 µg/day)
Bone and muscle aches usually ease over 6–8 weeks; blood levels normalise in about 8–12 weeks of steady intake.
Sources & references
Symptoms overlap — testing matters
Most deficiency symptoms (fatigue, poor concentration, skin and hair changes) are shared across several nutrients and many unrelated conditions. A symptom on this page is a reason to investigate, not a diagnosis.
A GP can confirm or rule out a deficiency with a blood test and check for underlying causes such as absorption problems. Do not start high-dose supplements on suspicion alone — some nutrients are harmful in excess, and supplementing before testing can mask the underlying result.