Ultra Vitamin D 3000 IU from Vitabiotics is the strongest vitamin D available to ensure optimum levels of vitamin D are maintained during the year. Vitamin D contributes to the normal function of the immune system. Ultra Vitamin D contains 75μg of vitamin D which equates to 3000 IU and is the highest strength of vitamin D avilable within the Vitabiotics vitamin D range. Ultra Vitamin D 3000 IU from Vitabiotics UK's No.1 vitamin D brand.