A 58-year-old man with BMI 32 kg/m² is diagnosed with type 2 diabetes mellitus. After 3 months of structured lifestyle intervention his HbA1c remains 7.8% (62 mmol/mol) and fasting glucose is 8.5 mmol/L. His eGFR is 75 mL/min/1.73 m² and there is no albuminuria or cardiovascular disease. What is the most appropriate next step in management?