Alfacalcidol is a synthetic form of Vitamin D3, which is used in the treatment of hypocalcemia (low calcium levels) and osteoporosis (bone weakening and loss). It is a prodrug that gets converted in the liver and kidneys to its active form, calcitriol, which regulates calcium and phosphorus levels in the body. Alfacalcidol is also used to treat renal osteodystrophy, a condition that occurs due to kidney failure, and helps in the absorption of calcium from the intestines, as well as in the maintenance of bone health. It is available in various forms such as capsules, oral solutions, and injections.