Vitamin D has been shown to related to clinical outcomes in critically ill patients. The object of this study is to investigate the prevalence of Vitamin D deficiency in critically ill patients with various length of ICU stay .

Studies have revealed that the serum level of 25-hydroxyvitamin D, as known as calcidiol, is low in critically ill patients. The prevalence ranges from 26 to 82%. 25-hydroxyvitamin D deficiency is associated with longer ICU stay, higher medical cost and higher death rate in septic patients. 25-hydroxyvitamin D is a kind of hormone related to bone and mineral metabolism. Moreover, the receptors were found in almost all cells, and it is related to immune system, cytokine release, cellular proliferation and differentiation, angiogenesis, and muscular energy. The main source is skin metabolism triggered by sunshine and food consumption. It is subsequently converted to calcifediol in the liver and then calcitriol in the kidney (the active form). Its serum level is regulated by parathyroid hormone and serum calcium and phosphate. The critically ill patients are deprived of sunshine, suffered from poor nutrition support, impaired liver and kidney function, higher rate of consumption, and are under higher risk of deficiency. Nowadays, the studies about 25-hydroxyvitamin D in ICU patients were conducted mostly in Europe and America. There is no large-scale study in Taiwan or Asia. A randomized controlled study from Austria has shown large dose supply in patients with 25-hydroxyvitamin D deficiency could decrease the mortality.

The object of this multi-center study is to investigate the prevalence of 25-hydroxyvitamin D deficiency, the risk factors and the correlation with outcomes. The results could be a step-stone for future randomized controlled studies.

Inclusion Criteria:

• All ICU patients

Exclusion Criteria:

• 1, Less than 20 years 2, BMI < 18 kg/m^2 3, Had large dose vit D within previous four weeks (over 3000 IU per day) 4, ICU admission within previous three months 5, Have disease affecting vit D level, calcium metabolism, bone metabolism such as parathyroid disease, Rickets, liver cirrhosis child C 6, Communication difficulty

This is a multi-center, cross-sectional study involving four medical center in Taipei, Taiwan, which are National Taiwan University Hospital (NTUH), Far Eastern Memorial Hospital (FEMH), MacKay Memorial Hospital (MMH), and Taipei Medical University Hospital (TMUH). The target population is all the ICU patients, divided into four groups according to the length of ICU stay. The serum level of vit D, ICU event such as infection, ventilator dependency is to be recorded.