Abstract: International Journal of General Medicine Dovepress open access to scientific and medical research International Journal of General Medicine For personal use only. Open Access Full Text Article ORIGINAL RESEARCH Clinical and Prognostic Significance of Baseline Serum Vitamin D Levels in Hospitalized Egyptian Covid-19 Patients Sadek Mostafa 1 , Shaymaa A Mohammed 2 , Salwa I Elshennawy 2 , Doaa Mohammed Zakaria 1 , Sammar Ahmed Kasim Mahmoud 1 , Amira Mohammed Alsadek 3 , Inass Hassan Ahmad 4 , Doaa Sayed Mohammed 4 , Marwa Abdelmonim Mohammed 1 , Heba H Eltrawy 3 1 Internal Medicine Department, Al-Azhar University, Cairo, Egypt; 2Clinical Pathology Department, Al-Azhar University, Cairo, Egypt; 3Chest Diseases Department, Al-Azhar University, Cairo, Egypt; 4Endocrinology and Metabolism Department, Al-Azhar University, Cairo, Egypt Correspondence: Heba H Eltrawy, Chest Diseases Department, Al-Azhar University, Cairo, Egypt, Tel +201006381297, Email hebahamed182@gmail.com Background and Aim: Vitamin D is a hormone with essential roles in both cellular metabolism and immunity. It controls calcium homeostasis and modulates innate and adaptive immune system responses. Many studies suggested an association between vitamin D deficiency and clinical outcomes of covid-19 infection, while others failed to document such a relation. The present study aimed to evaluate the clinical and prognostic significance of baseline vitamin D levels in hospitalized Egyptian covid-19 patients. Patients and Methods: The present retrospective study included 300 hospitalized covid-19 patients. Patients were submitted to standard clinical, laboratory, and radiological assessment. According to vitamin D levels, patients were classified to have normal levels (≥30), insufficient levels (20–29) or deficient levels (<20). Results: According to their vitamin D levels, patients were classified into those with normal vitamin D (n=135), others with vitamin D insufficiency (n=114), and a third group with vitamin D deficiency (n=51). Patients with normal vitamin D levels and vitamin D insufficiency are significantly younger [median (IQR): 49.0 (39.0–57.0) versus 51.0 (40.0–61.0) and 55.0 (43.0–62.0) years, respectively, p=0.012] and had less frequency of severe disease (24.4% versus 40.4% and 51.0%, respectively) when compared with those with vitamin D deficiency. Moreover, they had significantly lower levels of D dimer [median (IQR): 1.5 (0.9–2.5) versus 1.8 (0.9–3.1) and 2.0 (1.0–3.2)], CRP [median (IQR): 58.0 (30.0–120.0) versus 76.0 (42.5–160.0) and 105.0 (74.0–208.0), respectively, p<0.001], ferritin [median (IQR): 458.0 (240.0–759.0) versus 606.0 (433.8–897.8) and 820.0 (552.0–1087.0), respectively, p<0.001], and procalcitonin [median (IQR): 290.0 (152.0–394.0) versus 372.5 (227.0–530.5) and 443.0 (272.0–575.0), respectively, p<0.001]. Only lower vitamin D levels were significant predictors of mortality in multivariate analysis [OR (95% CI): 0.88 (0.84–0.92), p<0.001]. Conclusion: Low vitamin D levels are related to exaggerated inflammatory response, disease severity, and poor clinical outcome in hospitalized covid-19 patients. Keywords: covid-19, vitamin D, vitamin D deficiency