Public Health England recommends that ALL people should consider taking a daily supplement of vitamin D in autumn and winter. The likelihood of vitamin D insufficiency is increased in malabsorption syndromes, aging (elderly individuals have a reduced capacity for vitamin D3 formation), darker skin (higher concentrations of melanin reduce efficiency in vitamin D3 production), obesity (fat-soluble vitamin D is stored in adipose, which reduces bioavailability), and minimal sun exposure, such as in winter or at more northern latitudes. 

Total Vitamin D (measured as 25-OH-D) generally refers to both its natural and synthetic forms. Vitamin D2 is synthetic, while D3 is naturally found in food and activated by sun exposure. To provide you with more complete information about your own intake, we test measure both forms, 25-hydroxyvitamin D3 (cholecalciferol), and 25-hydroxyvitamin D2 (ergocalciferol). -‘[