MRCP-0426

A 70-year-old man presents to the emergency department acutely unwell. He is shocked, drowsy and confused. He is known to be type-2 diabetic maintained on metformin. Blood tests reveal a metabolic acidosis with an anion gap of 24 mmol/l. Ketones are not significantly elevated and random blood glucose was 8.7 mmol/l. What is the mainstay of treatment for this condition?