Prognostic nutritional index (PNI) is a novel inflammation marker that useful in predicting prognosis of certain conditions. We aimed to study PNI of the outpatient and inpatient subjects with established Covid-19 and also aimed to compare PNI of deceased and survived Covid-19 patients.Methods The patients with Covid-19 whom presented to outpatient or inpatient clinics of Abant Izzet Baysal University Hospital were enrolled to the study. PNI levels of the inpatients and outpatients, deceased and survived were compared. PNI values of deceased and survived in inpatients were also compared. ResultsStudy population was consisted of 4419 subjects (2907 outpatients and 1512 inpatients). PNI of the inpatient (41.55 (36.42-47.1)) group was significantly lower than the PNI of the outpatient (51.95 (47.95-55.75)) subjects (p<0.001). The sensitivity and specificity of PNI (≤46.2 level) in determination of requirement inpatient treatment were 71.2% and 83.5%, respectively. PNI of the deceased patients (37(33.39-40.86)) was lower than the PNI of the survivors (50.45(45.6-54.65)), (p<0.001). The sensitivity and specificity of PNI at ≤44.55 level in determining mortality were 89.22% and 78.87%, respectively. Conclusion We suggest that PNI could serve as a reliable prognostic index in covid-19 patients. Reduced level of PNI should alert physicians since it is associated with need for hospitalization and mortality in this population.