Methods, compositions, and kits for adjunctive therapy using 25-hydroxyvitamin D are disclosed. The 25-hydroxyvitamin D may be administered with an agent that increases the risk of hypocalcemia, such as cinacalcet or a salt thereof, and/or an anticancer agent. The adjunctive therapy is effective to treat and prevent iatrogenic hypocalcemia and/or secondary hyperparathyroidism, as well as delay cancer progression and the time to a post-treatment skeletal related event.
