A 52-year-old retired schoolteacher is brought to the emergency department by her daughter, exhibiting recurrent episodes of confusion and somnolence. These episodes have occurred several times over the past two months, consistently resolving shortly after consuming sugary drinks or snacks. Her daughter reports that these events are becoming more frequent and severe, often accompanied by sweating and palpitations. The patient has no significant past medical history, takes no regular medications, and has no family history of diabetes. On examination, her temperature is 36.8°C, blood pressure is 128/78 mmHg, pulse is 92/min, respirations are 18/min, and oxygen saturation is 99% on room air. She is disoriented to time and place, responding slowly to verbal stimuli, and has fine tremors in her outstretched hands. Pupils are equal and reactive to light, and deep tendon reflexes are symmetrical. A bedside glucose check reveals a value of 1.7 mmol/L. Which of the following represents the most likely diagnosis and the critical initial management step for this patient's condition?