Objective To evaluate the relationships between admission fasting serum C-peptide concentration and cardiac function status in chronic heart failure (CHF) patients with or without diabetes. Methods From July 2017 to December 2018, 262 CHF patients with or without diabetes in the Department of Cardiology of Pudong hospital in Shanghai were analyzed.Their cardiac function was classified as New York Heart Association (NYHA) grade Ⅱ to Ⅳ, and they were divided into diabetes group (80 cases) and non diabetes group (182 cases). At the same time, 62 subjects without diabetes and heart disease were randomly selected as the control group.To analyze the relationship between fasting serum C-peptide level and cardiac function in diabetic and nondiabetic CHF patients. Results (1)The fasting plasma glucose and serum C-peptide concentrations of diabetes group paitents were(8.7±2.9) mmol/L and(0.78±0.67) nmol/L respectively, the nondiabetes group paitents were(5.8±1.67) mmol/L and(0.56±0.61)nmol/L respectively, the control group were(5.1±0.69) mmol/L and(0.16±0.12)nmol/L respectively.The difference in the three groups was statistically significant(all P 0.05). (2) In all patients with heart failure, diabetes mellitus and non diabetes heart failure, the levels of serum C-peptide were (1.05±0.85), (1.17±0.82), (0.99±0.86) nmol/L in NYHA Ⅳ group, and (0.53±0.22), (0.52±0.20), (0.54±0.23) nmol/L in NYHA Ⅲ group, and (0.32±0.09), (0.32±0.11), (0.31±0.09) nmol/L in NYHA Ⅱ group.After adjustment of age, gender, smoking, insulin secretion and hypoglycemic drugs, body mass index, blood pressure, total bilirubin (TBIL), alanine aminotransferase (ALT), creatinine, blood glucose, blood lipid, white blood cell count (WBC) and hemoglobin level by covariance analysis, all patients with heart failure The level of serum C-peptide in NYHA Ⅳ group was significantly higher than that in Ⅲ group (all P 0.05) (3) Using multiple linear regression analysis, the adjustment factors included age, gender, smoking, BMI, blood pressure, TBIL, alt, creatinine, blood glucose, blood lipid, WBC and hemoglobin levels.The results showed that the serum C-peptide level was positively correlated with pro-BNP in all patients with heart failure, diabetes and non diabetes heart failure (β: 0.006, 95%CI -0.016-0.028 , P=0.007; β: 0.117, 95%CI-0.042-0.277 , P=0.006; β: 0.411, 95%CI-0.149-0.971 , P=0.023), negatively correlated with LVEF(β: -0.122, 95%CI-0.285-0.041, P=0.004; β: -0.008, 95%CI-0.032-0.016, P=0.010; β: -0.065, 95%CI-0.139-0.011, P=0.036). Conclusion The level of fasting serum C-peptide was significantly increased in patients with CHF and non-diabetic patients, and was related to the severity of heart failure. Key words: Chronic heart failure; Diabetes mellitus; Serum C-peptide; N-terminal B-type natriuretic peptide; Cardiac function