Results: This study was conducted on 297 critically ill children in ICU department of Children hospital 2 the year 2016, without hypophosphatemia at admission, were followed up nutrition support ratio, hypophosphatemia, refeeding syndrome in 1 week, > 2 weeks length stay in PICU, 2 weeks mortality ratio in 2 weeks, reported at day 0 (D0), day 3 - 4 (D3), day 7 - 8 (D7) and day 15 (D15).