Trauma has been an important global public health issue. Yet it is the sixth cause of death in Taiwan, trauma brings great negative impact to national productivity since it presents specifically as the leading cause of death for the population aged below 40 years. According to the national databank from Formosa Association for the Surgery of Trauma, mortality rate in critically traumatic patients with injury severity score (ISS) ≥ 25 is as high as 23%. Vitamin D, a pleiotropic hormone, regulates directly functions of most organs and immune system. It has been proven that vitamin D insufficiency or deficiency would deteriorate survival of critically ill patients, while supplementation of high-dose vitamin D ameliorates the clinical outcomes. This study investigates whether multiple high doses of vitamin D supplementation in one week can decrease the mortality and morbidity in critically traumatic patients. The serum levels of calcidiol and PTH will be measured on Day 0, Day 3, Day 10, Day 15, Day 30 and Day 60 before and after vitamin D supplementation.