U shape association of hemoglobin level with in-hospital mortality for COVID-19 patients.

Our hypothesis was that high hemoglobin (Hb) level might be associated with hypercoagulable state and death due to COVID-19. Of the 9467 hospitalized COVID-19 patients, patients were subdivided into 5 groups based on the level of Hb; Hb < 10 g/dL, 10 g/dL ≤ Hb < 12 g/dL, 12 g/dL ≤ Hb < 14 g/dL, 14 g/dL ≤ Hb < 16 g/dL, and Hb ≥ 16 g/dL. Compared to patients with 12 g/dL ≤ Hb < 14 g/dL, patients with Hb ≥ 16 g/dL had significantly higher adjusted in-hospital mortality (OR [95% CI] 1.62 [1.15-2.27], P = 0.005).