Vitamin D deficiency
Vitamin D is essential for maintaining healthy bones, teeth and muscles. It helps the body absorb calcium and phosphate from food and plays a role in immune function.
The body produces vitamin D when the skin is exposed to sunlight, but in the UK, particularly during autumn and winter, many people do not get enough. The Department of Health recommends that adults and children over 1 year consider taking a daily supplement of 10 micrograms of vitamin D during these months.
People at higher risk of deficiency include those who spend little time outdoors, people with darker skin, those who cover most of their skin for cultural reasons, older adults and people with conditions affecting fat absorption.
Symptoms of deficiency can include fatigue, bone and muscle pain, muscle weakness and, in severe cases, bone conditions such as rickets in children and osteomalacia in adults. A blood test for 25-hydroxyvitamin D is the standard measure of vitamin D status.
Causes of Vitamin D deficiency
Vitamin D deficiency occurs when the body does not receive or produce enough vitamin D.
The main causes are:
- Insufficient sunlight exposure, the primary source of vitamin D for most people. In the UK, UVB radiation is only strong enough to stimulate vitamin D production in the skin from approximately April to September
- Darker skin, which requires more sun exposure to produce the same amount of vitamin D as lighter skin due to higher melanin content
- Covering the skin for cultural, religious or occupational reasons
- Being housebound or spending very little time outdoors
- Dietary insufficiency, as few foods are naturally rich in vitamin D (oily fish, egg yolks, fortified foods)
- Malabsorption from conditions such as coeliac disease, Crohn's disease and cystic fibrosis
- Obesity, as vitamin D is sequestered in fat tissue, reducing its availability in the bloodstream
- Chronic kidney or liver disease, which impairs conversion of vitamin D to its active form
Tests that can help check this condition
Learn more on the official NHS page .
