What is vitamin D?
Vitamin D is a hormone that helps the body to absorb calcium. Calcium is needed to build and maintain healthy bones and keep our muscles strong.
Vitamin D is manufactured in the body when our bare skin is exposed to ultraviolet (UV) radiation from sunlight. Most people can get adequate vitamin D naturally this way.
A small amount of vitamin D comes from food — including oily fish, eggs, margarine and some milks — but it is very difficult to get enough vitamin D from diet alone.
Download our 'Vitamin D tests and deficiency' fact sheet to find out if you are at risk of deficiency, how to improve your vitamin D levels, and whether you need a vitamin D test.
What could happen if I don’t get enough vitamin D?
People with very low levels of vitamin D are at risk of having softer bones that are prone to breaking.
Children with very low vitamin D levels can develop rickets. Because the bones don’t form normally, the child can be short, with bowed legs. Very low calcium levels may result in your child having seizures (fits).
In adults over the age of 50, low vitamin D levels can lead to osteoporosis and increase the risk of falls and fractures (broken bones).
Many health conditions, including diabetes, heart disease and some cancers, have been linked to low vitamin D levels, but the exact role vitamin D plays in these conditions is unclear. The benefits of increasing vitamin D intake for these health problems — through sun exposure, diet or supplements — are unknown.