Drisdol is vitamin D2. Vitamin D helps your body absorb calcium. Drisdol is used to treat hypoparathyroidism (decreased functioning of the parathyroid glands). Drisdol is also used to treat rickets (softening of the bones caused by vitamin D deficiency) or low levels of phosphate in the blood (hypophosphatemia). Drisdol may also be used for purposes not listed in this medication guide.