A 32-year-old woman presents with menorrhagia for 6 months. Menarche at 12 years, cycles regular 28/5 days until 6 months ago. She denies intermenstrual bleeding, postcoital bleeding, or pelvic pain. Vitals stable, BMI 24 kg/m². General and pelvic examination unremarkable. Haemoglobin 9.8 g/dL. What is the next step in management?