Pure & Essential Vegan Vitamin D3 is a natural algae extractÊproviding cholecalciferol Ð the most biologically active form of vitamin D that is easily absorbed by the body and taken up into the bloodstream. Small tablets deliver 1000 IU of vitamin D3, suitable for everyday use throughout the year. Excessive doses of vitamin D3 can upset the delicate ratio of calcium and vitamin D in the body, so higher doses should only be taken for acute periods as needed.ÊÊ