AMC Part 1 August Recall

A 3-year-old has been unwell for several days with fever and has eaten almost nothing. He is brought to the emergency department after a generalised tonic-clonic seizure. Blood glucose is 1.9 mmol/L, blood ketones are strongly positive, and the liver is not enlarged. His parents describe a viral illness with fever and a sore throat starting four days ago, since when he has refused most food and taken only sips of water. The seizure lasted about two minutes and stopped without treatment. What is the most likely cause of the low glucose?