Hence, we investigated the serum levels of vitamin D3 (cholecalciferol) and its metabolites (calcifediol and calcitriol), in addition to their relative ratios and correlations with angiotensin-converting enzyme 2 (ACE2), interleukin-6 (Il-6), and neutrophil–lymphocyte ratio (NLR) in COVID-19 patients compared with healthy controls. This evidence concerns the gene IL6 and COVID-19.