Our formula contains 10ug (400iu) of Vitamin D3, however some people may need more. Supplementation of Vitamin D is officially recommended during autumn and winter, however if you are unwell, staying indoors for extended periods of time, elderly, have dark skin or are pregnant or breast-feeding, you will need to supplement all year round. We would also recommend taking our Vitamin D alongside this product in cases of a fracture or joint issues, and when managing a bone condition. If you would like any further advice please contact our Nutritional Team.