Not all vitamin D is made equal

Vitamin D is produced by the body through direct skin exposure to the Sun. You may be deficient in Vitamin D if you spend a lot of time indoors. Other sources of Vit D are Oily fish such as mackerel, sardines and Salmon also found in eggs. Home tests are available online if you think you may have low Vit D levels. 

Vitamin D supports healthy bones, muscle function and contributes to a healthy immune system.

Academics urge for a rethink on guidelines after study finds one form is twice as important to our health –

Source – https://www.dailymail.co.uk/health/article-4664814/Vitamin-D3-twice-important-health-D2.html