Upon admission (Table 2), patients with COVID-associated hyperglycaemia exhibited a significantly higher white blood cell count (9.7 (6.1–14.3) vs. 7.1 (5.4–10.4) × 109/L, p = 0.004), neutrophil count (8.4 (4.85–12.9) vs. 5.2 (3.9–8.1) × 109/L, p = 0.003), and tissue damage markers (LDH 8.04 (5.35–16.63) vs. 5.92 (4.42–8.17) μkat/L, p = 0.001; AST 0.95 (0.65–1.39) vs. 0.63 (0.42–1.14) μkat/L, p = 0.001; ALT 0.78 (0.47–1.24) vs. 0.53 (0.3–0.93) μkat/L, p = 0.012) compared to patients with pre-existing diabetes. This evidence concerns the gene GPT and diabetes mellitus.