Aims: To correlate serum magnesium levels with prognosis and clinical outcome of sepsis patients Materials and methods: In this prospective, observational case-control study, we analyzed a total of 100 cases, 50 cases (sepsis with low magnesium) and 50 controls (sepsis with normal magnesium), respectively. Results: There is statistically significant difference between the patient groups was seen with respect to the serum magnesium (p=0.001). The mean serum magnesium was found to be decreasing with increase in the Q-SOFA score among the patients in the case group.The mean serum magnesium was found to be decreasing with increase in the Q-SOFA score in control group, and statistically significant difference between the scores was seen. A statistically significant association between the patients groups and the need for mechanical ventilation, duration of ventilatory support, need for ionotropic support and mortality. Mean serum magnesium in the group of patients died was 1.13, while the mean serum magnesium in the group of patient’s lives was 1.46. A statistically significant difference between the patient groups (alive and dead ) was seen with respect to the serum magnesium (p=0.001). The mean Q-SOFA score in the group of patients died was 2.79, while the mean Q-SOFA score in the group of patient’s lives was 1.92, respectively. A statistically significant difference between the patient groups (alive and dead ) was seen with respect to the Q- SOFA scores (p=0.001). The sensitivity of the Q-SOFA cut-off value >2 was 90.62%, sensitivity of 51.47%, and the accuracy was 64%, respectively. Conclusion: Hypomagnesemia, when detected require correction for the management of those with critical illness for better outcomes.