Purpose: To explore the effects of primary and secondary hyperglycemia and the application of the hypoglycemic drug metformin on the prognosis of patients with diffuse large B-cell lymphoma (DLBCL). Methods: We performed a retrospective analysis of 1767 DLBCL patients.Cox regression method was used for analysis to evaluate the prognostic factors, and the Kaplan-Meier method was used to draw a survival curve to analyze the effect of hyperglycemia and the hypoglycemic drug metformin on the progression-free survival (PFS) and overallsurvival (OS) of DLBCL patients. Results: Our study showed that patients with hyperglycemia tend to have higher age (age > 60 years), high body mass index (BMI) (>= 24kg/m(2)), late Ann Arbor stage (III-IV), high international prognostic index (IPI) (3-5 score), high lactic dehydrogenase (LDH) level (> 250U/L), bulky disease and comorbidity. Hyperglycemia affects the survival time of the DLBCL population (PFS: adjusted HR 1.41, 95% CI: 1.16-1.70, P < 0.001, OS: adjusted HR 1.33, 95% CI:1.09-1.61, P=0.004).Compared with the non-hyperglycemia group, the secondary hyperglycemia increase affects the prognosis of the DLBCL population (P < 0.001). Compared with the secondary hyperglycemia group, the primary hyperglycemia group has a poor prognosis (P < 0.05). For patients with DLBCL and hyperglycemia (732 patients in total), the use of metformin can improve their PFS and OS (PFS: adjusted HR 0.69, 95% CI: 0.49-0.96, P=0.028, OS: adjusted HR 0.68, 95% CI: 0.49-0.95, P=0.024). Conclusion: Hyperglycemia and secondary hyperglycemia are related to the poor prognosis of DLBCL population.For patients with DLBCL combined with hyperglycemia, the application of metformin can improve survival rate.