Background: Community-acquired pneumonia (CAP) represents a substantial burden to the Health care system. Pneumonia imposes a staggering clinical and economic burden to our community. Despite being the cause of significant morbidity and mortality, pneumonia is often misdiagnosed, wrongly treated, and underestimated. No perfect bio-marker or scoring system is available to this date to evaluate the severity of CAP patients. The incidence of hyponatremia at hospital admission among CAP patients is found to be 28%and is associated with not only prolongation of hospitalization but also an increase in hospital mortality. Aim of the study: 1. To evaluate hyponatremia as a possible bio-marker to assess severity of community acquired pneumonia (CAP). 2. To compare hyponatremia with CURB-65 as an initial screening tool for assessment of severity of CAP. Materials and methods: 100 patients with CAP who were hospitalized were included in study. Serum sodium levels were measured on day 1,3 and 7 after initial assessment of patients and were analyzed with the clinical profile and outcome in these study groups. Results: CAP was more commonly seen between age group 31-40 years (22%), among males (61%), Type 2 diabetes mellitus was the major co morbidity associated (23%), smoking was an important risk factor (33%). Majority of them belonged to Pneumonia severity index (PSI) risk class 3 and above. Serum sodium levels showed a significant correlation from day 1 to the day of discharge in both resolving and un-resolving pneumonias, and also at the time of admission as compared to CURB-65 score. Conclusion: In our study patients with severe hyponatremia had high in – hospital morbidity and mortality, whereas those with rising sodium levels showed signs of improvement. This proves that serum sodium levels can be used as a prognostic biomarker in community acquired pneumonia which is cost effective and easily available.