A 2-year-old girl from a coastal fishing community presents with irritability, poor feeding, and swollen wrists and ankles for 2 weeks. On examination, she has tender swelling over the wrists and ankles, bleeding gums, and petechial rashes on the lower limbs. Her mother reports that the child eats mainly rice and dried fish, with no fresh fruits or vegetables for the past 3 months due to seasonal unavailability. Hemoglobin is 10.5 g/dL. What is the most appropriate next step in management?