Active vitamin D (1,25-hydroxyvitamin D₃) is used clinically as a drug, including osteotriol and alfacalcitol. 1. Osteotriol: Osteotriol enters the human body without the transformation of liver and kidney can directly play a role, and after combining with the vitamin D receptor in the tissue cells, it is used to regulate the body’s absorption and metabolism of calcium and phosphorus. It can be used in the treatment of rickets, osteomalacia, renal osteodystrophy and other diseases. 2. Alfacalcitol: Alfacalcitol regulates calcium metabolism in muscles by increasing calcium reabsorption in the small intestine and decreasing synthesis and release of parathyroid gland. It is mainly used to improve the abnormalities of vitamin D metabolism, such as renal bone disease and osteochondrosis. In addition, some new vitamin D analogs, such as paricalcitol and dulcitol, which have similar biological effects as active vitamin D, are also used in the clinic. Please do not self-medicate, but standardize the diagnosis and treatment under the guidance of your doctor.