Vitamin A refers to a group of fat-soluble substances that are structurally related to and possess the biological activity of the parent substance of the group called All-trans-retinol or retinol.
Vitamin D refers to the secosterols ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3) as well as to the metabolites and analogues of these substances.
Vitamin D2 is derived from fungal and plant sources. It's fat soluble or stored in the body.
Vitamin D3 is derived from animal sources. It's not stored in the body.
As a dietary supplement, 1 tablet daily, or as recommended by your health care professional.