Background: Hypomagnesemia in patients with critical illnesses ranged from 20% to 60% in various studies conducted throughout the world. It is among the most typical electrolyte problem that goes undiagnosed in severely unwell patients. Low magnesium levels can be utilised as a determinant of the severity and prognosis of patients who are critically ill. Objectives: Theobjectivesofthestudyaretocorrelatehypomagnesemia with the clinical and other biochemical parameters and also clinical outcome inthosepatients. Materials and Method: A total of 78 subjects were enrolled in the study. Serum magnesium, calcium, sodium, creatinine and blood urea were evaluated. Results obtained were analyzed using SPSS 20.0 version and the association was tested using independentt-test. A p value less than 0.05 was considered significant. Results: Among the study population, 37patientshad hypomagnesemiaand41 patients had normal serum magnesium level. Among the 37 patients who had hypomagnesemia, 51.35% were females and 48.65% were males. The mean APACHE score was high in patients with hypomagnesemia. The ‘p’ value of APACHE II was less than 0.05 showed that there was significant difference between these two groups. Comparison of serum magnesium level with serum potassium, serum calcium, sepsis and diabetes also showed statistical significance. The need for ventilation and mortality was high in patients with hypomagnesemia compared to normomagnesemia patients 26 vs 17 and 21 vs 11 respectively.