Background: Clinical status of children admitted to the intensive care units (ICUs) is important. We aimed to investigate prevalence of hypomagnesaemia in children admitted to the pediatric intensive care unit (PICU), and its relation factors.
Materials and Methods: This cross-sectional study was conducted in Ali Ebne Abitalib Hospital Zahedan, Iran, in 2018. From total children who were admitted to the PICU, 150 individuals aged one month to 12 years that were entered to the study. Magnesium level was estimated by XYLIDYL BLUE method using Erba kits. Children were divided into two groups based on their serum magnesium concentration defined as normal and abnormal.  Data were analyzed using SPSS software version 18.0. 
Results: From 150 admitted children to the PICU, 44.7% were hypomagnesaemia with longer hospital stay, higher levels of Na, K and Ca (p>0.05). During the first five day of hospitalization, 58 children died, most of them were hypomagnesaemia. About 39.6% of 101 children who consumed diuretic medicine were hypomagnesemia. This pattern was 43.8% and 40.00% from 130 and 85 patients who used digital or aminoglycoside medicines. About half of the children who had heart diseases were hypomagnesemia. These trends were 33.3% in kidney and sepsis; about 50.00% and 43.5% were hypomagnesaemia from those who had central nervous disorder and respiratory problems, respectively. The eldest children had 1.79 times higher odds (95% CI=0.76 to 8.30) to be hypomagnesaemia compared to the youngest, and girls had 1.01 times higher odds (95% CI=0.44 to 2.30) to be hypomagnesaemia.
Conclusion: Prevalence of hypomagnesaemia in children admitted to the PICU was high and it was associated with the major electrolytes of sodium, potassium, and calcium.