The aim of our study was to evaluate the influence of asymptomatic infection and the occurrence of symptomatic COVID-19 on specific biochemical, renal, and immune parameters—renalase, neutrophil gelatinase-associated lipocalin (NGAL) cystatin C (CysC), and creatinine—and their weekly fluctuations during a one-month observation period in COVID-19 patients admitted to hospital. The gene discussed is RNLS; the disease is COVID-19.