Calcitriol is an analogue to the vitamin D which is used to prevent low levels of calcium and bone disease in patients whose kidneys are not working properly or parathyroid glands are not functioning well. The parathyroid glands produces natural substances to control the amount of calcium in the blood. Calcitriol also used to treat condition in which the body produces too much parathyroid hormone due to kidney diseases. This drug helps the body to absorb more calcium from the foods or supplements to regulating the body functioning. In case of overdose this medicine may lead to temporary bad health effects like weakness, headache, upset stomach, dry mouth, muscle pain, change in vision and difficult or painful urination.