Metformin in Post Chronic Pancreatitis Diabetes Mellitus

Inclusion Criteria: 1. Aged 18-65 years, any sex. 2. Patients diagnosed with chronic pancreatitis. 3. Diagnose diabetes at least 3 months after chronic pancreatitis diagnosis. 4. Never used any diabetes drug/glucose-lowering medication or had discontinued any glucose-lowering medications for at least 8 weeks prior to screening. 5. HbA1c criteria: 7.5%\~9.0%. 6. BMI \>18.5. 7. Provision of signed informed consent. Exclusion Criteria: 1. Type 1 diabetes or secondary diabetes not caused by chronic pancreatitis (e.g. diabetes due to monogenic defects, cystic fibrosis, medications, autoimmune diseases, stress, or other factors). 2. Contraindications or history of intolerance or allergy to metformin. 3. Fasting C-peptide \<0.3 nmol/L. 4. Acute episodes of chronic pancreatitis at enrollment or within 3 months prior to enrollment. 5. History of congestive heart failure (NYHA class 3 or greater), unstable angina, or other severe cardiovascular diseases. 6. History of cancer (except non-melanoma skin cancer) within 5 years prior to screening. 7. History of partial or total pancreatectomy. 8. History of or planning bariatric surgery. 9. Previous organ transplantation. 10. Treatment with oral or systemic glucocorticoids within 3 months prior to enrollment or plan to use during the study (inhaled steroids are permitted). 11. History of hemolytic anemia, chronic transfusion requirements, or other conditions rendering HbA1c results unreliable. 12. Other conditions requiring glucose-lowering medications, such as polycystic ovary syndrome. 13. Fasting blood glucose \>11.1 mmol/L during screening, requiring immediate treatment as judged by the physician. 14. Sever psychiatric disorders or health conditions deemed unsuitable for clinical research participation. 15. Pregnancy or plans for pregnancy during the course of the study. 16. Any other condition considered by the investigator to be inappropriate for participation in the trial.