Vitamin D3 is a steroid derivative, is a fat-soluble vitamins, the human body is a very important class of vitamins in the body's main role is to regulate the metabolism of calcium and phosphorus, and the health status of the body and a great relationship. The main active forms of vitamin D are 25-hydroxyvitamin D3, 1,25-dihydroxyvitamin D3 and 24,25-dihydroxyvitamin D3. Among them, 25 - hydroxy vitamin D3 is the body 's blood in the main form of vitamin D, when the body will cause a lack of disease. The test results of this kit should be combined with other clinical and experimental data to assist clinicians in assessing vitamin D3 metabolic status.