- OBJECTIVE: SARS-CoV-2 might present with multisystem involvement due to its entry into many cells with ACE2 receptors on their surfaces, such as heart, endothelial, and lung al-veoli cells. Studies have indicated that COVID-19 infection causes a severe clinical presentation in diabetic patients due to dysregulation of the meta-bolic and immune systems. The hematological ef-fects of COVID-19 and the relationship of lympho-penia with the severity of the disease have been reported previously. The parameter of percent-age of large unstained cells (LUCs) reflects active lymphocytes and peroxidase-negative cells. The neutrophil-to-lymphocyte ratio (NLR) is another reliable marker of inflammation in cases of cardi-ac diseases, solid tumors, and sepsis. The present study aimed to evaluate whether the parame-ters of LUCs and NLR differed between diabetic and nondiabetic individuals with COVID-19. Asso-ciations with disease severity were also sought.MATERIALS AND METHODS: In our retro-spective study, the data of 1,053 patients [230 diabetic patients (21.83%) and 823 nondiabetic patients (78.15%)] were reviewed. The white blood cell (WBC) count, neutrophil count, neutrophil%, lymphocyte count, lymphocyte%, LUC count, %LUCs, NLR, platelet count, hemoglobin level, HbA1c, history of diabetes, surveillance during hospitalization, and pulmonary infiltration status within the first 24 hours after admission to the hospital were analyzed from the records.RESULTS: When diabetic patients were com-pared with nondiabetics, the age [65 (20-90) vs. 42 (18-94) years], WBC count [6.72 (2.6-24.04) vs. 5.91 (1.35-52.68)], neutrophil count [4.29 (1.28-65) vs. 3.68 (0.02-50.47)], neutrophil% [67.53 +/- 12.3 vs.64.08 +/- 13.28], NLR [3.35 (0.83-38.11) vs. 2.48 (0.01-68.58)], and LUC count [0.11 (0.03-0.98) vs. 0.1 (0.02-3.06)] of the diabetic group were found to be higher and these differences were statistically significant (p<0.001, p<0.001, p<0.001, p<0.001, p<0.001, and p=0.015, respectively).CONCLUSIONS: We determined that LUC counts and NLR values in COVID-19-positive pa-tients with diabetes were statistically significant-ly higher compared to nondiabetic patients.