Background: Covid-19 infection is a highly infectious illness with high mortality especially among elderly patients with chronic illnesses . During the pandemic of Covid-19 , it is necessary to find a screening method to predict the patients at high risk for developing severe immortal disease . increased interleukin-6 (IL-6) is a key factor contributing to the cytokine storm syndrome involved in clinical manifestations of Covid-19.

Aim of the work: to determine the significance of Interleukin- 6 as a predictive factor of Hypoxemia and the severity of Covid-19 infection .

Subjects and Methods: Case - Control study was done at Abassia Fever hospital and Ain Shams University Isolation Hospitals on 75 persons (50 patients with different grades of severity for Covid-19 disease and 25 controls) during 6 months duration from September 2021 to March 2022 .

Results: we found a statistically significant difference as regard serum IL-6 between critically severe , mild and control groups with more increased levels of IL-6 between died patients than survived patients .

Conclusion: Neutrophil-Lymphocyte Ratio , CRP , ESR , Ferritin and Albumin were associated with increased disease severity and worse clinical outcome but IL-6 was found to be better than them in predicting disease severity . the level of IL-6 > 12.6 pg/mL at the initial presentation had excellent sensitivity and specificity in predicting the development of hypoxia demanding hospitalization . Further larger studies are needed to predict the significance of IL-6 as an effective screening method for the severe Covid-19 disease .