ALB and COVID-19: For the liver and kidney function biomarkers (Left panel of Figure 2), we observed that higher levels of albumin have a protective effect [OR from IVW method, 0.85 (95% CI: 0.73–0.98), P = 0.024] and higher levels of direct bilirubin have a risk effect [1.10 (1.01–1.19), P = 0.023] on severe COVID-19, and the other three MR methods revealed consistent results.