Methods and compositions for reducing serum parathyroid levels in, for example, chronic kidney disease patients are disclosed. In these methods, an effective amount of a modified release formulation of 25-hydroxyvitamin D is orally administered to a patient suffering from secondary hyperparathyroidism to lower the patient's serum intact parathyroid hormone (iPTH) level, while avoiding a surge in serum total 25-hydroxyvitamin D.