Role of Vitamin D Levels in COVID-19 Disease Severity: A Multicenter Retrospective Study from Qatar.

&lt;b&gt;Background and Objective:&lt;/b&gt; Up to now, evidence remains inconclusive about how vitamin D (VD) status relates to the severity of COVID-19 among hospitalized patients. The present study aims to explore the impact of VD status on the severity of COVID-19 among hospitalized patients in Qatar and examine its effects on health factors related to the disease. &lt;b&gt;Materials and Methods:&lt;/b&gt; A retrospective, cross-sectional, multicenter study was conducted at Hamad Medical Corporation in Qatar from March, 2020 to May, 2021. Demographics, laboratory values, comorbidities, clinical outcomes and some inflammatory markers were retrieved from the hospital's system. The severity of COVID-19 disease was determined by an elevated neutrophil-lymphocyte ratio (NLR). A patient with VD levels less than 20 ng/mL was considered deficient. Data were analyzed using SPSS v22, with significance set at p<0.05, employing Mann-Whitney, Chi-squared and correlation tests as appropriate. &lt;b&gt;Results:&lt;/b&gt; The VD deficiency was common (68.6%), with longer ICU stays observed in deficient patients compared to those with normal VD status (19.7 vs. 11.2; p = 0.04). There was a trend of higher NLR with lower VD levels. No significant difference in interleukin-6 levels was found between the deficient and sufficient VD groups (60.6±64.1 vs. 41.2±45.2 pg/mL; p = 0.472). &lt;b&gt;Conclusion:&lt;/b&gt; This study highlights the link between VD status and COVID-19 disease severity. The findings suggest that suboptimal levels of VD in COVID-19 patients may be potentially associated with increased length of stay in the ICU and have a minor impact on the pro-inflammatory state.