Abstract: Open Access Original Article DOI: 10.7759/cureus.26266 The Association Between Vitamin D Serum Level and COVID-19 Patients’ Outcomes in a Tertiary Center in Saudi Arabia: A Retrospective Cohort Study Review began 05/31/2022 Review ended 06/19/2022 Published 06/23/2022 © Copyright 2022 Alzahrani et al. This is an open access article distributed under the terms of the Mahmoud A. Alzahrani 1 , Faisal Almalki 2 , Ayman Aljohani 2 , Bassam Alharbi 2 , Bandar Alsulami 2 , Ahmed Alhaddad 2 , Alaa Althubaiti 3 , Bader Khawaji 4 , Fayssal Farahat 5 Creative Commons Attribution License CCBY 4.0., which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. 1. Specialized Polyclinic Primary Health Care Department, National Guard Health Affairs (NGHA), Jeddah, SAU 2. College of Medicine, King Saud Bin Abdulaziz University for Health Sciences College of Medicine, Jeddah, SAU 3. College of Medicine, King Saud Bin Abdulaziz University for Health Sciences, Jeddah, SAU 4. Basic Medical Sciences, College of Medicine, King Saud Bin Abdulaziz University for Health Sciences College of Medicine, Jeddah, SAU 5. Infection Prevention and Control, King Abdulaziz Medical City, Riyadh, SAU Corresponding author: Ayman Aljohani, aymalje@gmail.com Abstract Vitamin D deficiency has been associated with the risk for immune-mediated inflammatory reactions in various respiratory infections. Our study investigated the association between vitamin D deficiency and coronavirus disease 2019 (COVID-19) patients’ outcomes. We included 545 patients who were admitted to a tertiary center in Jeddah, Saudi Arabia from March 2020 to July 2021 with a vitamin D serum test result at the time of infection or prior to disease onset. The data were extracted retrospectively using a data collection sheet. Our primary outcomes were intensive care unit (ICU) admission and in-hospital mortality. The cut-off values for vitamin D were <25, 25-49, and 50-250 for deficient, suboptimal, and optimal levels respectively. Our result revealed that there is no association between vitamin D serum levels deficiency and ICU admission (OR=1.08, p=0.75) or in-hospital mortality (OR=1.74, p=0.97). ICU admission and in-hospital mortality percentages in patients with vitamin D deficiency were 14.1% and 6.4%, respectively. In comparison, percentages for patients with optimal levels were 16.67% and 6.15% for ICU admission and inhospital mortality, respectively. Smoking was not associated with ICU admission (p=0.05) or in-hospital mortality (p=0.38). Our study does not support a relationship between vitamin D deficiency and COVID-19 patients’ outcomes. Future studies should be directed toward conducting randomized clinical trials to determine whether vitamin D has an effective role in reducing COVID-19 severity. Categories: Family/General Practice, Internal Medicine, Infectious Disease Keywords: severe covid-19, family medicine, infectious disease, vitamin-d deficiency, covid 19