A 24-year-old woman presents to her GP with polyuria, polydipsia and fatigue over 2 months. BMI is 32 kg/m². Fasting venous plasma glucose is 8.5 mmol/L on two separate mornings. HbA1c is 7.4% (57 mmol/mol). She has no ketonuria and is clinically well. According to Australian guidelines, what is the most appropriate initial pharmacological management?