Osteotrienol pills are a drug that promotes the absorption of calcium in the human body. They are actually 1-25 dihydroxyvitamin D3 formed by the dual metabolism of vitamin D3 by hydroxylase in the liver and kidneys, and are the most active vitamin-like drugs known for their anti-rickets activity. It is used clinically for rickets, osteoporosis in menopausal women and the elderly, idiopathic or postoperative hypoparathyroidism, chronic renal failure, and also for the treatment of osteochondrosis. The principle of its action is to promote the absorption of calcium by the intestine, inhibit the excretion of calcium by the kidneys, and also stimulate the activity of existing osteoclasts to accelerate the formation of new osteoclasts, thus promoting the absorption of bone and increasing the concentration of calcium in the blood, which is rapidly converted by the small intestine after oral administration, so it does not require metabolic activation and is therefore very suitable for the treatment of calcium in patients with hepatic or renal insufficiency.