Active vitamin D is a steroid derivative. Unlike common vitamins, active vitamin D is converted in the body to produce different forms of hydroxylated metabolites, which are not only necessary for bone development, maintenance and repair, but also have various extra-bone functions. Active vitamin D is used clinically as a drug, not as a nutrient, and includes osteotriol and alfa osteotriol.1. Osteotriol: Osteotriol enters the body without activation and has a rapid onset of action, but a relatively short duration of action. It is mainly used for postmenopausal and senile osteoporosis, vitamin D-dependent rickets, etc. During treatment with osteopontinol, blood and urine calcium levels need to be monitored regularly because excessive use of osteopontinol may lead to hypercalcemia or hypercalciuria. When the blood calcium and urine calcium levels are abnormally elevated, the drug should be discontinued in time, and then the doctor should decide the dosing plan after the recovery to the normal range; 2. Alfazocalciferol: Alfazocalciferol needs further activation and has a slow onset of action, but the duration of action is relatively long. It is mainly used to improve chronic renal insufficiency, osteochondrosis, osteoporosis, etc.; 3, other active vitamin D: mainly new vitamin D analogues, including paricalcitol, dulcitol, marsupialol, etc., which belong to a class of drugs with similar chemical structure and biological effects as active vitamin D. It is mainly used for the treatment of hyperparathyroidism caused by chronic renal failure, which leads to abnormal vitamin D metabolism.