Doxercalciferol is a hydroxy seco-steroid and synthetic vitamin D2 analogue that undergoes metabolic activation in vivo to form 1alpha,25-dihydroxyvitamin D2 (1alpha,25-(OH)2D2), a naturally occurring, biologically active form of vitamin D2. It is used to treat secondary hyperparathyroidism, a condition in which the body produces excess parathyroid hormone (PTH; a natural substance needed to control the amount of calcium in the blood) in certain people with chronic kidney disease. It has a role as a provitamin, a bone density conservation agent and a prohormone. It is a vitamin D and a hydroxy seco-steroid.