Background: Biochemical markers in COVID-19 remain to be defined. We analyzed the usefulness of LDH and ferritin in predicting outcome. Methods: This retrospective study analyzed ferritin and LDH concentrations obtained during the first 11 days of hospitalization in COVID-19 patients. We compared the change in ferritin and LDH concentrations obtained on each day of hospital admission with respect to baseline values between patients with favorable and unfavorable outcomes. We used receiver operating curve analysis to determine cutoffs for predicting outcomes. Results: We analyzed 387 patients. For determinations done on the 9th day, increases in LDH concentrations > 14.6% over the baseline yielded 80% positive predictive value, and a lack of increase yielded 96% negative predictive value for unfavorable outcomes. The change in ferritin concentration yielded lower predictive values. Conclusion: The percentage of change in LDH with respect to the baseline on the 9th day of hospitalization can predict outcome..