A 68-year-old woman presents with mild confusion for two days. She has had a worsening headache for the past two weeks. There is no history of fever; respiratory, urinary or gastrointestinal symptoms; or recent trauma. She was diagnosed with type 2 diabetes mellitus five years ago, which is uncomplicated and well controlled on metformin 850 mg once daily. She is not on any other medications. She only drinks socially and does not smoke. Her family history is unremarkable. A full blood count, liver profile, renal profile, and serum electrolytes are all within normal parameters. Her capillary blood glucose is 160 mg/dL.