We aimed to examine independent predictive factors for the severity and survival of COVID-19 disease, from routine blood parameters, especially the blood urea nitrogen (BUN)/creatinine (Cr) ratio. A total of 139 patients with COVID-19 were investigated at Siirt State Hospital. According to the disease severity, the patients were categorized as three groups (moderate: 85, severe: 54, and critical: 20). Then, patients were divided into two groups: nonsevere (moderate) and severe (severe and critical). Demographic, clinical data, and routine blood parameters were analyzed. In multivariate model adjusted for potential confounders BUN/Cr ratio (odds ratio [OR] = 1.70; 95% confidence interval [CI]: 1.20-2.40; P = .002) and neutrophil to lymphocyte ratio (NLR) (OR = 2.21; 95% CI: 1.20-4.30; P < .001) were independent predictive factors for disease severity. In multivariate Cox proportional hazard model BUN/Cr ratio (hazard ratio [HR] = 1.02; 95% CI: 1.01-1.05; P = .030), and NLR (HR = 1.17; 95% CI: 1.06-1.30; P = .020) were independent predictors for survival of COVID-19 disease. The optimal thresholds of the BUN/Cr ratio at 33.5 and 51.7 had the superior possibility for severe disease and mortality, area under the curve (AUC) were 0.98 and 0.95, respectively. The optimal thresholds of NLR at 3.27 and 5.72 had a superior possibility for severe disease and mortality, AUC were 0.87 and 0.85, respectively. BUN/Cr and NLR are independent predictors for COVID-19 patient severity and survival. Routine evaluation of BUN/Cr and NLR can help identify high-risk cases with COVID-19.